More file format docs.

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diff --git a/doc/cs-notes.txt b/doc/cs-notes.txt
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+cstypes
+
+bezier
+
+Type bezier specifies a sequence of Bezier curves of similar degree, each
+beginning where the prior terminated.  If there are multiple curves in the
+sequence, then the initial control point of a latter curve is not explicitly
+specified since it is equal to the last control point of the prior curve.
+
+Consider the following example.
+
+    curv2 -6 -5 -4 -3 -2 -1 -6
+
+When the degree is 3, the above specifies two Bézier curves: C₁=(-6,-5,-4,-3) and
+C₂=(-3,-2,-1,-6).
+
+The Bézier curve functions are taken to be branches of a peicewise function C
+obtianed by dividing the parameter space into regions and mapping each region
+to a different curve.  For example,
+
+    parm u 0.00 1.00 2.00
+
+specifies two intervals, [0,1] and [1,2].  If the parameter is between 0 and 1,
+it will be mapped via the first curve C₁ and if it is between 1 and 2, it will
+be mapped via the second curve C₂.  In order to maintain continuity, an affine
+transformation will be applied first to obtain a value between 0 and 1 so that
+C(1.5) = C₂(0.5).
+
diff --git a/doc/mtl-format.txt b/doc/mtl-format.txt
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+                     MTL material format (Lightwave, OBJ)
+
+                    Excerpt from FILE FORMATS, Version 4.2
+                                 October 1995
+      Documentation created by: Diane Ramey, Linda Rose, and Lisa Tyerman
+                     Copyright 1995 Alias|Wavefront, Inc.
+                              All rights reserved
+
+
+
+5.  Material Library File (.mtl)
+
+ Material library files contain one or more material definitions, each
+of which includes the color, texture, and reflection map of individual
+materials.  These are applied to the surfaces and vertices of objects.
+Material files are stored in ASCII format and have the .mtl extension.
+
+ An .mtl file differs from other Alias|Wavefront property files, such as
+light and atmosphere files, in that it can contain more than one
+material definition (other files contain the definition of only one
+item).
+
+ An .mtl file is typically organized as shown below.
+
+
+        newmtl my_red
+                Material color
+                & illumination
+                statements
+
+                texture map
+                statements
+
+                reflection map
+                statement
+
+        newmtl my_blue
+                Material color
+                & illumination
+                statements
+
+                texture map
+                statements
+
+                reflection map
+                statement
+
+        newmtl my_green
+                Material color
+                & illumination
+                statements
+
+                texture map
+                statements
+
+                reflection map
+                statement
+
+        Figure 5-1.  Typical organization of .mtl file
+
+
+ Each material description in an .mtl file consists of the newmtl
+statement, which assigns a name to the material and designates the start
+of a material description.  This statement is followed by the material
+color, texture map, and reflection map statements that describe the
+material.  An .mtl file map contain many different material
+descriptions.
+
+ After you specify a new material with the "newmtl" statement, you can
+enter the statements that describe the materials in any order.  However,
+when the Property Editor writes an .mtl file, it puts the statements in
+a system-assigned order.  In this chapter, the statements are described
+in the system-assigned order.
+
+
+ Format
+
+ The following is a sample format for a material definition in an .mtl
+file:
+
+ Material
+ name
+ statement:
+                newmtl my_mtl
+
+ Material
+ color and
+ illumination
+ statements:
+                Ka 0.0435 0.0435 0.0435
+                Kd 0.1086 0.1086 0.1086
+                Ks 0.0000 0.0000 0.0000
+                Tf 0.9885 0.9885 0.9885
+                illum 6
+                d -halo 0.6600
+                Ns 10.0000
+                sharpness 60
+                Ni 1.19713
+
+ Texture
+ map
+ statements:
+                map_Ka -s 1 1 1 -o 0 0 0 -mm 0 1 chrome.mpc
+                map_Kd -s 1 1 1 -o 0 0 0 -mm 0 1 chrome.mpc
+                map_Ks -s 1 1 1 -o 0 0 0 -mm 0 1 chrome.mpc
+                map_Ns -s 1 1 1 -o 0 0 0 -mm 0 1 wisp.mps
+                map_d -s 1 1 1 -o 0 0 0 -mm 0 1 wisp.mps
+                disp -s 1 1 .5 wisp.mps
+                decal -s 1 1 1 -o 0 0 0 -mm 0 1 sand.mps
+                bump -s 1 1 1 -o 0 0 0 -bm 1 sand.mpb
+
+ Reflection
+ map
+ statement:
+                refl -type sphere -mm 0 1 clouds.mpc
+
+
+ Material Name
+
+ The material name statement assigns a name to the material description.
+
+ Syntax
+ The folowing syntax describes the material name statement.
+
+        newmtl name
+
+ Specifies the start of a material description and assigns a name to the
+material.  An .mtl file must have one newmtl statement at the start of
+each material description.
+
+        "name" is the name of the material.  Names may be any length but
+cannot include blanks.  Underscores may be used in material names.
+
+
+ Material color and illumination
+
+ The statements in this section specify color, transparency, and
+reflectivity values.
+
+ Syntax
+ The following syntax describes the material color and illumination
+statements that apply to all .mtl files.
+
+
+        Ka r g b
+        Ka spectral file.rfl factor
+        Ka xyz x y z
+
+ To specify the ambient reflectivity of the current material, you can
+use the "Ka" statement, the "Ka spectral" statement, or the "Ka xyz"
+statement.
+
+ Tip    These statements are mutually exclusive.  They cannot be used
+concurrently in the same material.
+
+ Ka r g b
+
+ The Ka statement specifies the ambient reflectivity using RGB values.
+
+ "r g b" are the values for the red, green, and blue components of the
+color.  The g and b arguments are optional.  If only r is specified,
+then g, and b are assumed to be equal to r.  The r g b values are
+normally in the range of 0.0 to 1.0.  Values outside this range increase
+or decrease the relectivity accordingly.
+
+ Ka spectral file.rfl factor
+
+ The "Ka spectral" statement specifies the ambient reflectivity using a
+spectral curve.
+
+ "file.rfl" is the name of the .rfl file.
+ "factor" is an optional argument.
+ "factor" is a multiplier for the values in the .rfl file and defaults
+to 1.0, if not specified.
+
+ Ka xyz x y z
+
+ The "Ka xyz" statement specifies the ambient reflectivity using CIEXYZ
+values.
+
+ "x y z" are the values of the CIEXYZ color space.  The y and z
+arguments are optional.  If only x is specified, then y and z are
+assumed to be equal to x.  The x y z values are normally in the range of
+0 to 1.  Values outside this range increase or decrease the reflectivity
+accordingly.
+
+
+        Kd r g b
+        Kd spectral file.rfl factor
+        Kd xyz x y z
+
+ To specify the diffuse reflectivity of the current material, you can
+use the "Kd" statement, the "Kd spectral" statement, or the "Kd xyz"
+statement.
+
+ Tip    These statements are mutually exclusive.  They cannot be used
+concurrently in the same material.
+
+ Kd r g b
+
+ The Kd statement specifies the diffuse reflectivity using RGB values.
+
+ "r g b" are the values for the red, green, and blue components of the
+atmosphere.  The g and b arguments are optional.  If only r is
+specified, then g, and b are assumed to be equal to r.  The r g b values
+are normally in the range of 0.0 to 1.0.  Values outside this range
+increase or decrease the relectivity accordingly.
+
+ Kd spectral file.rfl factor
+
+ The "Kd spectral" statement specifies the diffuse reflectivity using a
+spectral curve.
+
+ "file.rfl" is the name of the .rfl file.
+ "factor" is an optional argument.
+ "factor" is a multiplier for the values in the .rfl file and defaults
+to 1.0, if not specified.
+
+ Kd xyz x y z
+
+ The "Kd xyz" statement specifies the diffuse reflectivity using CIEXYZ
+values.
+
+ "x y z" are the values of the CIEXYZ color space.  The y and z
+arguments are optional.  If only x is specified, then y and z are
+assumed to be equal to x.  The x y z values are normally in the range of
+0 to 1.  Values outside this range increase or decrease the reflectivity
+accordingly.
+
+
+        Ks r g b
+        Ks spectral file.rfl factor
+        Ks xyz x y z
+
+ To specify the specular reflectivity of the current material, you can
+use the "Ks" statement, the "Ks spectral" statement, or the "Ks xyz"
+statement.
+
+ Tip    These statements are mutually exclusive.  They cannot be used
+concurrently in the same material.
+
+ Ks r g b
+
+ The Ks statement specifies the specular reflectivity using RGB values.
+
+ "r g b" are the values for the red, green, and blue components of the
+atmosphere.  The g and b arguments are optional.  If only r is
+specified, then g, and b are assumed to be equal to r.  The r g b values
+are normally in the range of 0.0 to 1.0.  Values outside this range
+increase or decrease the relectivity accordingly.
+
+ Ks spectral file.rfl factor
+
+ The "Ks spectral" statement specifies the specular reflectivity using a
+spectral curve.
+
+ "file.rfl" is the name of the .rfl file.
+ "factor" is an optional argument.
+ "factor" is a multiplier for the values in the .rfl file and defaults
+to 1.0, if not specified.
+
+ Ks xyz x y z
+
+ The "Ks xyz" statement specifies the specular reflectivity using CIEXYZ
+values.
+
+ "x y z" are the values of the CIEXYZ color space.  The y and z
+arguments are optional.  If only x is specified, then y and z are
+assumed to be equal to x.  The x y z values are normally in the range of
+0 to 1.  Values outside this range increase or decrease the reflectivity
+accordingly.
+
+
+        Tf r g b
+        Tf spectral file.rfl factor
+        Tf xyz x y z
+
+ To specify the transmission filter of the current material, you can use
+the "Tf" statement, the "Tf spectral" statement, or the "Tf xyz"
+statement.
+
+ Any light passing through the object is filtered by the transmission
+filter, which only allows the specifiec colors to pass through.  For
+example, Tf 0 1 0 allows all the green to pass through and filters out
+all the red and blue.
+
+ Tip    These statements are mutually exclusive.  They cannot be used
+concurrently in the same material.
+
+ Tf r g b
+
+ The Tf statement specifies the transmission filter using RGB values.
+
+ "r g b" are the values for the red, green, and blue components of the
+atmosphere.  The g and b arguments are optional.  If only r is
+specified, then g, and b are assumed to be equal to r.  The r g b values
+are normally in the range of 0.0 to 1.0.  Values outside this range
+increase or decrease the relectivity accordingly.
+
+ Tf spectral file.rfl factor
+
+ The "Tf spectral" statement specifies the transmission filterusing a
+spectral curve.
+
+ "file.rfl" is the name of the .rfl file.
+ "factor" is an optional argument.
+ "factor" is a multiplier for the values in the .rfl file and defaults
+to 1.0, if not specified.
+
+ Tf xyz x y z
+
+ The "Ks xyz" statement specifies the specular reflectivity using CIEXYZ
+values.
+
+ "x y z" are the values of the CIEXYZ color space.  The y and z
+arguments are optional.  If only x is specified, then y and z are
+assumed to be equal to x.  The x y z values are normally in the range of
+0 to 1.  Values outside this range will increase or decrease the
+intensity of the light transmission accordingly.
+
+
+ illum illum_#
+
+ The "illum" statement specifies the illumination model to use in the
+material.  Illumination models are mathematical equations that represent
+various material lighting and shading effects.
+
+ "illum_#"can be a number from 0 to 10.  The illumination models are
+summarized below; for complete descriptions see "Illumination models" on
+page 5-30.
+
+ Illumination    Properties that are turned on in the
+ model           Property Editor
+
+ 0              Color on and Ambient off
+ 1              Color on and Ambient on
+ 2              Highlight on
+ 3              Reflection on and Ray trace on
+ 4              Transparency: Glass on
+                Reflection: Ray trace on
+ 5              Reflection: Fresnel on and Ray trace on
+ 6              Transparency: Refraction on
+                Reflection: Fresnel off and Ray trace on
+ 7              Transparency: Refraction on
+                Reflection: Fresnel on and Ray trace on
+ 8              Reflection on and Ray trace off
+ 9              Transparency: Glass on
+                Reflection: Ray trace off
+ 10             Casts shadows onto invisible surfaces
+
+
+ d factor
+
+ Specifies the dissolve for the current material.
+
+ "factor" is the amount this material dissolves into the background.  A
+factor of 1.0 is fully opaque.  This is the default when a new material
+is created.  A factor of 0.0 is fully dissolved (completely
+transparent).
+
+ Unlike a real transparent material, the dissolve does not depend upon
+material thickness nor does it have any spectral character.  Dissolve
+works on all illumination models.
+
+ d -halo factor
+
+ Specifies that a dissolve is dependent on the surface orientation
+relative to the viewer.  For example, a sphere with the following
+dissolve, d -halo 0.0, will be fully dissolved at its center and will
+appear gradually more opaque toward its edge.
+
+ "factor" is the minimum amount of dissolve applied to the material.
+The amount of dissolve will vary between 1.0 (fully opaque) and the
+specified "factor".  The formula is:
+
+ dissolve = 1.0 - (N*v)(1.0-factor)
+
+ For a definition of terms, see "Illumination models" on page 5-30.
+
+
+ Ns exponent
+
+ Specifies the specular exponent for the current material.  This defines
+the focus of the specular highlight.
+
+ "exponent" is the value for the specular exponent.  A high exponent
+results in a tight, concentrated highlight.  Ns values normally range
+from 0 to 1000.
+
+
+ sharpness value
+
+ Specifies the sharpness of the reflections from the local reflection
+map.  If a material does not have a local reflection map defined in its
+material definition, sharpness will apply to the global reflection map
+defined in PreView.
+
+ "value" can be a number from 0 to 1000.  The default is 60.  A high
+value results in a clear reflection of objects in the reflection map.
+
+ Tip    Sharpness values greater than 100 map introduce aliasing effects
+in flat surfaces that are viewed at a sharp angle
+
+
+ Ni optical_density
+
+ Specifies the optical density for the surface.  This is also known as
+index of refraction.
+
+ "optical_density" is the value for the optical density.  The values can
+range from 0.001 to 10.  A value of 1.0 means that light does not bend
+as it passes through an object.  Increasing the optical_density
+increases the amount of bending.  Glass has an index of refraction of
+about 1.5.  Values of less than 1.0 produce bizarre results and are not
+recommended.
+
+
+ Material texture map
+
+ Texture map statements modify the material parameters of a surface by
+associating an image or texture file with material parameters that can
+be mapped.  By modifying existing parameters instead of replacing them,
+texture maps provide great flexibility in changing the appearance of an
+object's surface.
+
+ Image files and texture files can be used interchangeably.  If you use
+an image file, that file is converted to a texture in memory and is
+discarded after rendering.
+
+ Tip Using images instead of textures saves disk space and setup time,
+however, it introduces a small computational cost at the beginning of a
+render.
+
+ The material parameters that can be modified by a texture map are:
+
+ - Ka (color)
+ - Kd (color)
+ - Ks (color)
+ - Ns (scalar)
+ - d (scalar)
+
+ In addition to the material parameters, the surface normal can be
+modified.
+
+
+ Image file types
+
+ You can link any image file type that is currently supported.
+Supported image file types are listed in the chapter "About Image" in
+the "Advanced Visualizer User's Guide".  You can also use the "im_info -
+a" command to list Image file types, among other things.
+
+
+ Texture file types
+
+ The texture file types you can use are:
+
+ - mip-mapped texture files (.mpc, .mps, .mpb)
+ - compiled procedural texture files (.cxc, .cxs, .cxb)
+
+
+ Mip-mapped texture files
+
+ Mip-mapped texture files are created from images using the Create
+Textures panel in the Director or the "texture2D" program.  There are
+three types of texture files:
+
+ - color texture files (.mpc)
+ - scalar texture files (.mps)
+ - bump texture files (.mpb)
+
+ Color textures.  Color texture files are designated by an extension of
+".mpc" in the filename, such as "chrome.mpc".  Color textures modify the
+material color as follows:
+
+ - Ka - material ambient is multiplied by the texture value
+ - Kd - material diffuse is multiplied by the texture value
+ - Ks - material specular is multiplied by the texture value
+
+ Scalar textures.  Scalar texture files are designated by an extension
+of ".mps" in the filename, such as "wisp.mps".  Scalar textures modify
+the material scalar values as follows:
+
+ - Ns - material specular exponent is multiplied by the texture value
+ - d - material dissolve is multiplied by the texture value
+ - decal - uses a scalar value to deform the surface of an object to
+create surface roughness
+
+ Bump textures.  Bump texture files are designated by an extension of
+".mpb" in the filename, such as "sand.mpb".  Bump textures modify
+surface normals.  The image used for a bump texture represents the
+topology or height of the surface relative to the average surface.  Dark
+areas are depressions and light areas are high points.  The effect is
+like embossing the surface with the texture.
+
+
+ Procedural texture files
+
+ Procedural texture files use mathematical formulas to calculate sample
+values of the texture.  The procedural texture file is compiled, stored,
+and accessed by the Image program when rendering.  for more information
+see chapter 9, "Procedural Texture Files (.cxc, .cxb. and .cxs)".
+
+ Syntax
+
+ The following syntax describes the texture map statements that apply to
+.mtl files.  These statements can be used alone or with any combination
+of options.  The options and their arguments are inserted between the
+keyword and the "filename".
+
+ map_Ka -options args filename
+
+ Specifies that a color texture file or a color procedural texture file
+is applied to the ambient reflectivity of the material.  During
+rendering, the "map_Ka" value is multiplied by the "Ka" value.
+
+ "filename" is the name of a color texture file (.mpc), a color
+procedural texture file (.cxc), or an image file.
+
+ Tip    To make sure that the texture retains its original look, use the
+.rfl file "ident" as the underlying material.  This applies to the
+"map_Ka", "map_Kd", and "map_Ks" statements.  For more information on
+.rfl files, see chapter 8, "Spectral Curve File (.rfl)".
+
+ The options for the "map_Ka" statement are listed below.  These options
+are described in detail in "Options for texture map statements" on page
+5-18.
+
+        -blendu on | off
+        -blendv on | off
+        -cc on | off
+        -clamp on | off
+        -mm base gain
+        -o u v w
+        -s u v w
+        -t u v w
+        -texres value
+
+
+ map_Kd -options args filename
+
+ Specifies that a color texture file or color procedural texture file is
+linked to the diffuse reflectivity of the material.  During rendering,
+the map_Kd value is multiplied by the Kd value.
+
+ "filename" is the name of a color texture file (.mpc), a color
+procedural texture file (.cxc), or an image file.
+
+ The options for the map_Kd statement are listed below.  These options
+are described in detail in "Options for texture map statements" on page
+5-18.
+
+        -blendu on | off
+        -blendv on | off
+        -cc on | off
+        -clamp on | off
+        -mm base gain
+        -o u v w
+        -s u v w
+        -t u v w
+        -texres value
+
+
+ map_Ks -options args filename
+
+ Specifies that a color texture file or color procedural texture file is
+linked to the specular reflectivity of the material.  During rendering,
+the map_Ks value is multiplied by the Ks value.
+
+ "filename" is the name of a color texture file (.mpc), a color
+procedural texture file (.cxc), or an image file.
+
+ The options for the map_Ks statement are listed below.  These options
+are described in detail in "Options for texture map statements" on page
+5-18.
+
+        -blendu on | off
+        -blendv on | off
+        -cc on | off
+        -clamp on | off
+        -mm base gain
+        -o u v w
+        -s u v w
+        -t u v w
+        -texres value
+
+
+ map_Ns -options args filename
+
+ Specifies that a scalar texture file or scalar procedural texture file
+is linked to the specular exponent of the material.  During rendering,
+the map_Ns value is multiplied by the Ns value.
+
+ "filename" is the name of a scalar texture file (.mps), a scalar
+procedural texture file (.cxs), or an image file.
+
+ The options for the map_Ns statement are listed below.  These options
+are described in detail in "Options for texture map statements" on page
+5-18.
+
+        -blendu on | off
+        -blendv on | off
+        -clamp on | off
+        -imfchan r | g | b | m | l | z
+        -mm base gain
+        -o u v w
+        -s u v w
+        -t u v w
+        -texres value
+
+
+ map_d -options args filename
+
+ Specifies that a scalar texture file or scalar procedural texture file
+is linked to the dissolve of the material.  During rendering, the map_d
+value is multiplied by the d value.
+
+ "filename" is the name of a scalar texture file (.mps), a scalar
+procedural texture file (.cxs), or an image file.
+
+ The options for the map_d statement are listed below.  These options
+are described in detail in "Options for texture map statements" on page
+5-18.
+
+        -blendu on | off
+        -blendv on | off
+        -clamp on | off
+        -imfchan r | g | b | m | l | z
+        -mm base gain
+        -o u v w
+        -s u v w
+        -t u v w
+        -texres value
+
+
+ map_aat on
+
+ Turns on anti-aliasing of textures in this material without anti-
+aliasing all textures in the scene.
+
+ If you wish to selectively anti-alias textures, first insert this
+statement in the material file.  Then, when rendering with the Image
+panel, choose the anti-alias settings:  "shadows", "reflections
+polygons", or "polygons only".  If using Image from the command line,
+use the -aa or -os options.  Do not use the -aat option.
+
+ Image will anti-alias all textures in materials with the map_aat on
+statement, using the oversampling level you choose when you run Image.
+Textures in other materials will not be oversampled.
+
+ You cannot set a different oversampling level individually for each
+material, nor can you anti-alias some textures in a material and not
+others.  To anti-alias all textures in all materials, use the -aat
+option from the Image command line.  If a material with "map_aat on"
+includes a reflection map, all textures in that reflection map will be
+anti-aliased as well.
+
+ You will not see the effects of map_aat in the Property Editor.
+
+ Tip    Some .mpc textures map exhibit undesirable effects around the
+edges of smoothed objects.  The "map_aat" statement will correct this.
+
+
+ decal -options args filename
+
+ Specifies that a scalar texture file or a scalar procedural texture
+file is used to selectively replace the material color with the texture
+color.
+
+ "filename" is the name of a scalar texture file (.mps), a scalar
+procedural texture file (.cxs), or an image file.
+
+ During rendering, the Ka, Kd, and Ks values and the map_Ka, map_Kd, and
+map_Ks values are blended according to the following formula:
+
+ result_color=tex_color(tv)*decal(tv)+mtl_color*(1.0-decal(tv))
+
+ where tv is the texture vertex.
+
+ "result_color" is the blended Ka, Kd, and Ks values.
+
+ The options for the decal statement are listed below.  These options
+are described in detail in "Options for texture map statements" on page
+5-18.
+
+        -blendu on | off
+        -blendv on | off
+        -clamp on | off
+        -imfchan r | g | b | m | l | z
+        -mm base gain
+        -o u v w
+        -s u v w
+        -t u v w
+        -texres value
+
+
+ disp -options args filename
+
+ Specifies that a scalar texture is used to deform the surface of an
+object, creating surface roughness.
+
+ "filename" is the name of a scalar texture file (.mps), a bump
+procedural texture file (.cxb), or an image file.
+
+ The options for the disp statement are listed below.  These options are
+described in detail in "Options for texture map statements" on page 5-
+18.
+
+        -blendu on | off
+        -blendv on | off
+        -clamp on | off
+        -imfchan r | g | b | m | l | z
+        -mm base gain
+        -o u v w
+        -s u v w
+        -t u v w
+        -texres value
+
+
+ bump -options args filename
+
+ Specifies that a bump texture file or a bump procedural texture file is
+linked to the material.
+
+ "filename" is the name of a bump texture file (.mpb), a bump procedural
+texture file (.cxb), or an image file.
+
+ The options for the bump statement are listed below.  These options are
+described in detail in "Options for texture map statements" on page 5-
+18.
+
+        -bm mult
+        -clamp on | off
+        -blendu on | off
+        -blendv on | off
+        -imfchan r | g | b | m | l | z
+        -mm base gain
+        -o u v w
+        -s u v w
+        -t u v w
+        -texres value
+
+
+ Options for texture map statements
+
+ The following options and arguments can be used to modify the texture
+map statements.
+
+ -blenu on | off
+
+ The -blendu option turns texture blending in the horizontal direction
+(u direction) on or off.  The default is on.
+
+ -blenv on | off
+
+ The -blendv option turns texture blending in the vertical direction (v
+direction) on or off.  The default is on.
+
+ -bm mult
+
+ The -bm option specifies a bump multiplier.  You can use it only with
+the "bump" statement.  Values stored with the texture or procedural
+texture file are multiplied by this value before they are applied to the
+surface.
+
+ "mult" is the value for the bump multiplier.  It can be positive or
+negative.  Extreme bump multipliers may cause odd visual results because
+only the surface normal is perturbed and the surface position does not
+change.  For best results, use values between 0 and 1.
+
+ -boost value
+
+ The -boost option increases the sharpness, or clarity, of mip-mapped
+texture files -- that is, color (.mpc), scalar (.mps), and bump (.mpb)
+files.  If you render animations with boost, you may experience some
+texture crawling.  The effects of boost are seen when you render in
+Image or test render in Model or PreView; they aren't as noticeable in
+Property Editor.
+
+ "value" is any non-negative floating point value representing the
+degree of increased clarity; the greater the value, the greater the
+clarity.  You should start with a boost value of no more than 1 or 2 and
+increase the value as needed.  Note that larger values have more
+potential to introduce texture crawling when animated.
+
+ -cc on | off
+
+ The -cc option turns on color correction for the texture.  You can use
+it only with the color map statements:  map_Ka, map_Kd, and map_Ks.
+
+ -clamp on | off
+
+ The -clamp option turns clamping on or off.  When clamping is on,
+textures are restricted to 0-1 in the uvw range.  The default is off.
+
+ When clamping is turned on, one copy of the texture is mapped onto the
+surface, rather than repeating copies of the original texture across the
+surface of a polygon, which is the default.  Outside of the origin
+texture, the underlying material is unchanged.
+
+ A postage stamp on an envelope or a label on a can of soup is an
+example of a texture with clamping turned on.  A tile floor or a
+sidewalk is an example of a texture with clamping turned off.
+
+ Two-dimensional textures are clamped in the u and v dimensions; 3D
+procedural textures are clamped in the u, v, and w dimensions.
+
+ -imfchan r | g | b | m | l | z
+
+ The -imfchan option specifies the channel used to create a scalar or
+bump texture.  Scalar textures are applied to:
+
+ transparency
+ specular exponent
+ decal
+ displacement
+
+ The channel choices are:
+
+ r specifies the red channel.
+ g specifies the green channel.
+ b specifies the blue channel.
+ m specifies the matte channel.
+ l specifies the luminance channel.
+ z specifies the z-depth channel.
+
+ The default for bump and scalar textures is "l" (luminance), unless you
+are building a decal.  In that case, the default is "m" (matte).
+
+ -mm base gain
+
+ The -mm option modifies the range over which scalar or color texture
+values may vary.  This has an effect only during rendering and does not
+change the file.
+
+ "base" adds a base value to the texture values.  A positive value makes
+everything brighter; a negative value makes everything dimmer.  The
+default is 0; the range is unlimited.
+
+ "gain" expands the range of the texture values.  Increasing the number
+increases the contrast.  The default is 1; the range is unlimited.
+
+ -o u v w
+
+ The -o option offsets the position of the texture map on the surface by
+shifting the position of the map origin.  The default is 0, 0, 0.
+
+ "u" is the value for the horizontal direction of the texture
+
+ "v" is an optional argument.
+ "v" is the value for the vertical direction of the texture.
+
+ "w" is an optional argument.
+ "w" is the value used for the depth of a 3D texture.
+
+ -s u v w
+
+ The -s option scales the size of the texture pattern on the textured
+surface by expanding or shrinking the pattern.  The default is 1, 1, 1.
+
+ "u" is the value for the horizontal direction of the texture
+
+ "v" is an optional argument.
+ "v" is the value for the vertical direction of the texture.
+
+ "w" is an optional argument.
+ "w" is a value used for the depth of a 3D texture.
+ "w" is a value used for the amount of tessellation of the displacement
+map.
+
+ -t u v w
+
+ The -t option turns on turbulence for textures.  Adding turbulence to a
+texture along a specified direction adds variance to the original image
+and allows a simple image to be repeated over a larger area without
+noticeable tiling effects.
+
+ turbulence also lets you use a 2D image as if it were a solid texture,
+similar to 3D procedural textures like marble and granite.
+
+ "u" is the value for the horizontal direction of the texture
+turbulence.
+
+ "v" is an optional argument.
+ "v" is the value for the vertical direction of the texture turbulence.
+
+ "w" is an optional argument.
+ "w" is a value used for the depth of the texture turbulence.
+
+ By default, the turbulence for every texture map used in a material is
+uvw = (0,0,0).  This means that no turbulence will be applied and the 2D
+texture will behave normally.
+
+ Only when you raise the turbulence values above zero will you see the
+effects of turbulence.
+
+ -texres resolution
+
+ The -texres option specifies the resolution of texture created when an
+image is used.  The default texture size is the largest power of two
+that does not exceed the original image size.
+
+ If the source image is an exact power of 2, the texture cannot be built
+any larger.  If the source image size is not an exact power of 2, you
+can specify that the texture be built at the next power of 2 greater
+than the source image size.
+
+ The original image should be square, otherwise, it will be scaled to
+fit the closest square size that is not larger than the original.
+Scaling reduces sharpness.
+
+
+ Material reflection map
+
+ A reflection map is an environment that simulates reflections in
+specified objects.  The environment is represented by a color texture
+file or procedural texture file that is mapped on the inside of an
+infinitely large, space.  Reflection maps can be spherical or cubic.  A
+spherical reflection map requires only one texture or image file, while
+a cubic reflection map requires six.
+
+ Each material description can contain one reflection map statement that
+specifies a color texture file or a color procedural texture file to
+represent the environment.  The material itself must be assigned an
+illumination model of 3 or greater.
+
+ The reflection map statement in the .mtl file defines a local
+reflection map.  That is, each material assigned to an object in a scene
+can have an individual reflection map.  In PreView, you can assign a
+global reflection map to an object and specify the orientation of the
+reflection map.  Rotating the reflection map creates the effect of
+animating reflections independently of object motion.  When you replace
+a global reflection map with a local reflection map, the local
+reflection map inherits the transformation of the global reflection map.
+
+ Syntax
+
+ The following syntax statements describe the reflection map statement
+for .mtl files.
+
+ refl -type sphere -options -args filename
+
+ Specifies an infinitely large sphere that casts reflections onto the
+material.  You specify one texture file.
+
+ "filename" is the color texture file, color procedural texture file, or
+image file that will be mapped onto the inside of the shape.
+
+ refl -type cube_side -options -args filenames
+
+ Specifies an infinitely large sphere that casts reflections onto the
+material.  You can specify different texture files for the "top",
+"bottom", "front", "back", "left", and "right" with the following
+statements:
+
+ refl -type cube_top
+ refl -type cube_bottom
+ refl -type cube_front
+ refl -type cube_back
+ refl -type cube_left
+ refl -type cube_right
+
+ "filenames" are the color texture files, color procedural texture
+files, or image files that will be mapped onto the inside of the shape.
+
+ The "refl" statements for sphere and cube can be used alone or with
+ any combination of the following options.  The options and their
+arguments are inserted between "refl" and "filename".
+
+ -blendu on | off
+ -blendv on | off
+ -cc on | off
+ -clamp on | off
+ -mm base gain
+ -o u v w
+ -s u v w
+ -t u v w
+ -texres value
+
+ The options for the reflection map statement are described in detail in
+"Options for texture map statements" on page 18.
+
+
+ Examples
+
+ 1  Neon green
+
+ This is a bright green material.  When applied to an object, it will
+remain bright green regardless of any lighting in the scene.
+
+ newmtl neon_green
+ Kd 0.0000 1.0000 0.0000
+ illum 0
+
+ 2  Flat green
+
+ This is a flat green material.
+
+ newmtl flat_green
+ Ka 0.0000 1.0000 0.0000
+ Kd 0.0000 1.0000 0.0000
+ illum 1
+
+ 3  Dissolved green
+
+ This is a flat green, partially dissolved material.
+
+ newmtl diss_green
+ Ka 0.0000 1.0000 0.0000
+ Kd 0.0000 1.0000 0.0000
+ d 0.8000
+ illum 1
+
+ 4  Shiny green
+
+ This is a shiny green material.  When applied to an object, it shows a
+white specular highlight.
+
+ newmtl shiny_green
+ Ka 0.0000 1.0000 0.0000
+ Kd 0.0000 1.0000 0.0000
+ Ks 1.0000 1.0000 1.0000
+ Ns 200.0000
+ illum 1
+
+ 5  Green mirror
+
+ This is a reflective green material.  When applied to an object, it
+reflects other objects in the same scene.
+
+ newmtl green_mirror
+ Ka 0.0000 1.0000 0.0000
+ Kd 0.0000 1.0000 0.0000
+ Ks 0.0000 1.0000 0.0000
+ Ns 200.0000
+ illum 3
+
+ 6  Fake windshield
+
+ This material approximates a glass surface.  Is it almost completely
+transparent, but it shows reflections of other objects in the scene.  It
+will not distort the image of objects seen through the material.
+
+ newmtl fake_windsh
+ Ka 0.0000 0.0000 0.0000
+ Kd 0.0000 0.0000 0.0000
+ Ks 0.9000 0.9000 0.9000
+ d 0.1000
+ Ns 200
+ illum 4
+
+ 7  Fresnel blue
+
+ This material exhibits an effect known as Fresnel reflection.  When
+applied to an object, white fringes may appear where the object's
+surface is viewed at a glancing angle.
+
+ newmtl fresnel_blu
+ Ka 0.0000 0.0000 0.0000
+ Kd 0.0000 0.0000 0.0000
+ Ks 0.6180 0.8760 0.1430
+ Ns 200
+ illum 5
+
+ 8  Real windshield
+
+ This material accurately represents a glass surface.  It filters of
+colorizes objects that are seen through it.  Filtering is done according
+to the transmission color of the material.  The material also distorts
+the image of objects according to its optical density.  Note that the
+material is not dissolved and that its ambient, diffuse, and specular
+reflective colors have been set to black.  Only the transmission color
+is non-black.
+
+ newmtl real_windsh
+ Ka 0.0000 0.0000 0.0000
+ Kd 0.0000 0.0000 0.0000
+ Ks 0.0000 0.0000 0.0000
+ Tf 1.0000 1.0000 1.0000
+ Ns 200
+ Ni 1.2000
+ illum 6
+
+ 9  Fresnel windshield
+
+ This material combines the effects in examples 7 and 8.
+
+ newmtl fresnel_win
+ Ka 0.0000 0.0000 1.0000
+ Kd 0.0000 0.0000 1.0000
+ Ks 0.6180 0.8760 0.1430
+ Tf 1.0000 1.0000 1.0000
+ Ns 200
+ Ni 1.2000
+ illum 7
+
+ 10  Tin
+
+ This material is based on spectral reflectance samples taken from an
+actual piece of tin.  These samples are stored in a separate .rfl file
+that is referred to by name in the material.  Spectral sample files
+(.rfl) can be used in any type of material as an alternative to RGB
+values.
+
+ newmtl tin
+ Ka spectral tin.rfl
+ Kd spectral tin.rfl
+ Ks spectral tin.rfl
+ Ns 200
+ illum 3
+
+ 11  Pine Wood
+
+ This material includes a texture map of a pine pattern.  The material
+color is set to "ident" to preserve the texture's true color.  When
+applied to an object, this texture map will affect only the ambient and
+diffuse regions of that object's surface.
+
+ The color information for the texture is stored in a separate .mpc file
+that is referred to in the material by its name, "pine.mpc".  If you use
+different .mpc files for ambient and diffuse, you will get unrealistic
+results.
+
+ newmtl pine_wood
+ Ka spectral ident.rfl 1
+ Kd spectral ident.rfl 1
+ illum 1
+ map_Ka pine.mpc
+ map_Kd pine.mpc
+
+ 12  Bumpy leather
+
+ This material includes a texture map of a leather pattern.  The
+material color is set to "ident" to preserve the texture's true color.
+When applied to an object, it affects both the color of the object's
+surface and its apparent bumpiness.
+
+ The color information for the texture is stored in a separate .mpc file
+that is referred to in the material by its name, "brown.mpc".  The bump
+information is stored in a separate .mpb file that is referred to in the
+material by its name, "leath.mpb".  The -bm option is used to raise the
+apparent height of the leather bumps.
+
+ newmtl bumpy_leath
+ Ka spectral ident.rfl 1
+ Kd spectral ident.rfl 1
+ Ks spectral ident.rfl 1
+ illum 2
+ map_Ka brown.mpc
+ map_Kd brown.mpc
+ map_Ks brown.mpc
+ bump -bm 2.000 leath.mpb
+
+ 13  Frosted window
+
+ This material includes a texture map used to alter the opacity of an
+object's surface.  The material color is set to "ident" to preserve the
+texture's true color.  When applied to an object, the object becomes
+transparent in certain areas and opaque in others.
+
+ The variation between opaque and transparent regions is controlled by
+scalar information stored in a separate .mps file that is referred to in
+the material by its name, "window.mps".  The "-mm" option is used to
+shift and compress the range of opacity.
+
+ newmtl frost_wind
+ Ka 0.2 0.2 0.2
+ Kd 0.6 0.6 0.6
+ Ks 0.1 0.1 0.1
+ d 1
+ Ns 200
+ illum 2
+ map_d -mm 0.200 0.800 window.mps
+
+ 14  Shifted logo
+
+ This material includes a texture map which illustrates how a texture's
+origin may be shifted left/right (the "u" direction) or up/down (the "v"
+direction).  The material color is set to "ident" to preserve the
+texture's true color.
+
+ In this example, the original image of the logo is off-center to the
+left.  To compensate, the texture's origin is shifted back to the right
+(the positive "u" direction) using the "-o" option to modify the origin.
+
+ Ka spectral ident.rfl 1
+ Kd spectral ident.rfl 1
+ Ks spectral ident.rfl 1
+ illum 2
+ map_Ka -o 0.200 0.000 0.000 logo.mpc
+ map_Kd -o 0.200 0.000 0.000 logo.mpc
+ map_Ks -o 0.200 0.000 0.000 logo.mpc
+
+ 15  Scaled logo
+
+ This material includes a texture map showing how a texture may be
+scaled left or right (in the "u" direction) or up and down (in the "v"
+direction).  The material color is set to "ident" to preserve the
+texture's true color.
+
+ In this example, the original image of the logo is too small.  To
+compensate, the texture is scaled slightly to the right (in the positive
+"u" direction) and up (in the positive "v" direction) using the "-s"
+option to modify the scale.
+
+ Ka spectral ident.rfl 1
+ Kd spectral ident.rfl 1
+ Ks spectral ident.rfl 1
+ illum 2
+ map_Ka -s 1.200 1.200 0.000 logo.mpc
+ map_Kd -s 1.200 1.200 0.000 logo.mpc
+ map_Ks -s 1.200 1.200 0.000 logo.mpc
+
+ 16  Chrome with spherical reflection map
+
+ This illustrates a common use for local reflection maps (defined in a
+material).
+
+ this material is highly reflective with no diffuse or ambient
+contribution.  Its reflection map is an image with silver streaks that
+yields a chrome appearance when viewed as a reflection.
+
+ ka 0 0 0
+ kd 0 0 0
+ ks .7 .7 .7
+ illum 1
+ refl -type sphere chrome.rla
+
+
+ Illumination models
+
+ The following list defines the terms and vectors that are used in the
+illumination model equations:
+
+ Term   Definition
+
+ Ft     Fresnel reflectance
+ Ft     Fresnel transmittance
+ Ia     ambient light
+ I      light intensity
+ Ir     intensity from reflected direction
+        (reflection map and/or ray tracing)
+ It     intensity from transmitted direction
+ Ka     ambient reflectance
+ Kd     diffuse reflectance
+ Ks     specular reflectance
+ Tf     transmission filter
+
+ Vector Definition
+
+ H      unit vector bisector between L and V
+ L      unit light vector
+ N      unit surface normal
+ V      unit view vector
+
+ The illumination models are:
+
+ 0  This is a constant color illumination model.  The color is the
+specified Kd for the material.  The formula is:
+
+   color = Kd
+
+ 1  This is a diffuse illumination model using Lambertian shading. The
+color includes an ambient constant term and a diffuse shading term for
+each light source.  The formula is
+
+   color = KaIa + Kd { SUM j=1..ls, (N * Lj)Ij }
+
+ 2  This is a diffuse and specular illumination model using Lambertian
+shading and Blinn's interpretation of Phong's specular illumination
+model (BLIN77).  The color includes an ambient constant term, and a
+diffuse and specular shading term for each light source.  The formula
+is:
+
+   color = KaIa
+        + Kd { SUM j=1..ls, (N*Lj)Ij }
+        + Ks { SUM j=1..ls, ((H*Hj)^Ns)Ij }
+
+ 3  This is a diffuse and specular illumination model with reflection
+using Lambertian shading, Blinn's interpretation of Phong's specular
+illumination model (BLIN77), and a reflection term similar to that in
+Whitted's illumination model (WHIT80).  The color includes an ambient
+constant term and a diffuse and specular shading term for each light
+source.  The formula is:
+
+   color = KaIa
+        + Kd { SUM j=1..ls, (N*Lj)Ij }
+        + Ks ({ SUM j=1..ls, ((H*Hj)^Ns)Ij } + Ir)
+
+   Ir = (intensity of reflection map) + (ray trace)
+
+ 4  The diffuse and specular illumination model used to simulate glass
+is the same as illumination model 3.  When using a very low dissolve
+(approximately 0.1), specular highlights from lights or reflections
+become imperceptible.
+
+ Simulating glass requires an almost transparent object that still
+reflects strong highlights.  The maximum of the average intensity of
+highlights and reflected lights is used to adjust the dissolve factor.
+The formula is:
+
+   color = KaIa
+        + Kd { SUM j=1..ls, (N*Lj)Ij }
+        + Ks ({ SUM j=1..ls, ((H*Hj)^Ns)Ij } + Ir)
+
+ 5  This is a diffuse and specular shading models similar to
+illumination model 3, except that reflection due to Fresnel effects is
+introduced into the equation.  Fresnel reflection results from light
+striking a diffuse surface at a grazing or glancing angle.  When light
+reflects at a grazing angle, the Ks value approaches 1.0 for all color
+samples.  The formula is:
+
+   color = KaIa
+        + Kd { SUM j=1..ls, (N*Lj)Ij }
+        + Ks ({ SUM j=1..ls, ((H*Hj)^Ns)Ij Fr(Lj*Hj,Ks,Ns)Ij} +
+Fr(N*V,Ks,Ns)Ir})
+
+
+ 6  This is a diffuse and specular illumination model similar to that
+used by Whitted (WHIT80) that allows rays to refract through a surface.
+The amount of refraction is based on optical density (Ni).  The
+intensity of light that refracts is equal to 1.0 minus the value of Ks,
+and the resulting light is filtered by Tf (transmission filter) as it
+passes through the object.  The formula is:
+
+   color = KaIa
+        + Kd { SUM j=1..ls, (N*Lj)Ij }
+        + Ks ({ SUM j=1..ls, ((H*Hj)^Ns)Ij } + Ir)
+        + (1.0 - Ks) TfIt
+
+ 7  This illumination model is similar to illumination model 6, except
+that reflection and transmission due to Fresnel effects has been
+introduced to the equation.  At grazing angles, more light is reflected
+and less light is refracted through the object.  The formula is:
+
+   color = KaIa
+        + Kd { SUM j=1..ls, (N*Lj)Ij }
+        + Ks ({ SUM j=1..ls, ((H*Hj)^Ns)Ij Fr(Lj*Hj,Ks,Ns)Ij} +
+Fr(N*V,Ks,Ns)Ir})
+
+        + (1.0 - Kx)Ft (N*V,(1.0-Ks),Ns)TfIt
+
+ 8  This illumination model is similar to illumination model 3 without
+ray tracing.  The formula is:
+
+   color = KaIa
+        + Kd { SUM j=1..ls, (N*Lj)Ij }
+        + Ks ({ SUM j=1..ls, ((H*Hj)^Ns)Ij } + Ir)
+
+   Ir = (intensity of reflection map)
+
+ 9  This illumination model is similar to illumination model 4without
+ray tracing.  The formula is:
+
+
+   color = KaIa
+        + Kd { SUM j=1..ls, (N*Lj)Ij }
+        + Ks ({ SUM j=1..ls, ((H*Hj)^Ns)Ij } + Ir)
+
+   Ir = (intensity of reflection map)
+
+ 10  This illumination model is used to cast shadows onto an invisible
+surface.  This is most useful when compositing computer-generated
+imagery onto live action, since it allows shadows from rendered objects
+to be composited directly on top of video-grabbed images.  The equation
+for computation of a shadowmatte is formulated as follows.
+
+ color = Pixel color.  The pixel color of a shadowmatte material is
+always black.
+
+ color = black
+
+ M = Matte channel value.  This is the image channel which typically
+represents the opacity of the point on the surface.  To store the shadow
+in the matte channel of the image, it is calculated as:
+
+ M = 1 - W / P
+
+ where:
+
+ P = Unweighted sum.  This is the sum of all S values for each light:
+
+ P = S1 + S2 + S3 + .....
+
+ W = Weighted sum.  This is the sum of all S values, each weighted by
+the visibility factor (Q) for the light:
+
+ W = (S1 * Q1) + (S2 * Q2) + .....
+
+ Q = Visibility factor.  This is the amount of light from a particular
+light source that reaches the point to be shaded, after traveling
+through all shadow objects between the light and the point on the
+surface.  Q = 0 means no light reached the point to be shaded; it was
+blocked by shadow objects, thus casting a shadow.  Q = 1 means that
+nothing blocked the light, and no shadow was cast.  0 < Q < 1 means that
+the light was partially blocked by objects that were partially
+dissolved.
+
+ S = Summed brightness.  This is the sum of the spectral sample
+intensities for a particular light.  The samples are variable, but the
+default is 3:
+
+ S = samp1 + samp2 + samp3.
+
diff --git a/doc/obj-spec.txt b/doc/obj-spec.txt
new file mode 100644
index 0000000..2430367
--- /dev/null
+++ b/doc/obj-spec.txt
@@ -0,0 +1,292 @@
+Wavefront OBJ
+
+Also Known As: Wavefront Object, OBJ
+
+━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+Type                     3D Vector
+Colors                   Unlimited
+Compression              Uncompressed
+Maximum Image Size       Unlimited
+Multiple Images Per File Yes
+Numerical Format         NA
+Originator               Wavefront
+Platform                 UNIX
+Supporting Applications  Advanced Visualizer
+See Also                 Wavefront RLA
+
+Usage
+Used to store and exchange 3D data.
+
+Comments
+The Wavefront OBJ format is a useful standard for representing polygonal data
+in ASCII form.
+
+Vendor specifications are available for this format.
+
+━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+Wavefront OBJ (object) files are used by Wavefront's Advanced Visualizer
+application to store geometric objects composed of lines, polygons, and
+free-form curves and surfaces. Wavefront is best known for its high-end
+computer graphics tools, including modeling, animation, and image compositing
+tools. These programs run on powerful workstations such as those made by
+Silicon Graphics, Inc.
+
+Wavefront OBJ files are often stored with the extension ".obj" following the
+UNIX convention of lowercase letters for filenames. The most recently
+documented version of OBJ is v3.0, superseding the previous v2.11 release.
+
+Contents:
+File Organization
+File Details
+For Further Information
+
+In Wavefront's 3D software, geometric object files may be stored in ASCII
+format (using the ".obj" file extension) or in binary format (using the .MOD
+extension). The binary format is proprietary and undocumented, so only the
+ASCII format is described here.
+
+The OBJ file format supports lines, polygons, and free-form curves and
+surfaces. Lines and polygons are described in terms of their points, while
+curves and surfaces are defined with control points and other information
+depending on the type of curve. The format supports rational and non-rational
+curves, including those based on Bezier, B-spline, Cardinal (Catmull-Rom
+splines), and Taylor equations.
+
+File Organization
+
+OBJ files do not require any sort of header, although it is common to begin the
+file with a comment line of some kind. Comment lines begin with a hash mark
+(#). Blank space and blank lines can be freely added to the file to aid in
+formatting and readability. Each non-blank line begins with a keyword and may
+be followed on the same line with the data for that keyword. Lines are read and
+processed until the end of the file. Lines can be logically joined with the
+line continuation character ( \ ) at the end of a line.
+
+The following keywords may be included in an OBJ file. In this list, keywords
+are arranged by data type, and each is followed by a brief description.
+
+Vertex data:
+
+    v  Geometric vertices
+    vt Texture vertices
+    vn Vertex normals
+    vp Parameter space vertices
+
+Free-form curve/surface attributes:
+
+    deg    Degree
+    bmat   Basis matrix
+    step   Step size
+    cstype Curve or surface type
+
+Elements:
+
+    p     Point
+    l     Line
+    f     Face
+    curv  Curve
+    curv2 2D curve
+    surf  Surface
+
+Free-form curve/surface body statements:
+
+    parm Parameter values
+    trim Outer trimming loop
+    hole Inner trimming loop
+    scrv Special curve
+    sp   Special point
+    end  End statement
+
+Connectivity between free-form surfaces:
+
+    con Connect
+
+Grouping:
+
+    g  Group name
+    s  Smoothing group
+    mg Merging group
+    o  Object name
+
+Display/render attributes:
+
+    bevel      Bevel interpolation
+    c_interp   Color interpolation
+    d_interp   Dissolve interpolation
+    lod        Level of detail
+    usemtl     Material name
+    mtllib     Material library
+    shadow_obj Shadow casting
+    trace_obj  Ray tracing
+    ctech      Curve approximation technique
+    stech      Surface approximation technique
+
+File Details
+
+The most commonly encountered OBJ files contain only polygonal faces. To
+describe a polygon, the file first describes each point with the "v" keyword,
+then describes the face with the "f" keyword. The line of a face command
+contains the enumerations of the points in the face, as 1-based indices into
+the list of points, in the order they occurred in the file. For example, the
+following describes a simple triangle:
+
+# Simple Wavefront file
+v 0.0 0.0 0.0
+v 0.0 1.0 0.0
+v 1.0 0.0 0.0
+f 1 2 3
+
+It is also possible to reference points using negative indices. This makes it
+easy to describe the points in a face, then the face, without the need to store
+a large list of points and their indexes. In this way, "v" commands and "f"
+commands can be interspersed.
+
+v -0.500000 0.000000 0.400000
+v -0.500000 0.000000 -0.800000
+v -0.500000 1.000000 -0.800000
+v -0.500000 1.000000 0.400000
+f -4 -3 -2 -1
+
+OBJ files do not contain color definitions for faces, although they can
+reference materials that are stored in a separate material library file. The
+material library can be loaded using the "mtllib" keyword. The material library
+contains the definitions for the RGB values for the material's diffuse,
+ambient, and specular colors, along with other characteristics such as
+specularity, refraction, transparency, etc.
+
+The OBJ file references materials by name with the "usemtl" keyword. All faces
+that follow are given the attributes of this material until the next "usemtl"
+command is encountered.
+
+Faces and surfaces can be assigned into named groups with the "g" keyword. This
+is used to create convenient sub-objects to make it easier to edit and animate
+3D models. Faces can belong to more than one group.
+
+The following demonstrate more complicated examples of smooth surfaces of
+different types, material assignment, line continuation, and grouping.
+
+Cube with Materials
+
+# This cube has a different material
+# applied to each of its faces.
+    mtllib master.mtl
+    v   0.000000        2.000000        2.000000
+    v   0.000000        0.000000        2.000000
+    v   2.000000        0.000000        2.000000
+    v   2.000000        2.000000        2.000000
+    v   0.000000        2.000000        0.000000
+    v   0.000000        0.000000        0.000000
+    v   2.000000        0.000000        0.000000
+    v   2.000000        2.000000        0.000000
+    # 8 vertices
+    g front
+    usemtl red
+    f 1 2 3 4
+    g back
+    usemtl blue
+    f 8 7 6 5
+    g right
+    usemtl green
+    f 4 3 7 8
+    g top
+    usemtl gold
+    f 5 1 4 8
+    g left
+    usemtl orange
+    f 5 6 2 1
+    g bottom
+    usemtl purple
+    f 2 6 7 3
+    # 6 elements
+
+Bezier Patch
+
+# 3.0 Bezier patch
+v -5.000000 -5.000000 0.000000
+v -5.000000 -1.666667 0.000000
+v -5.000000 1.666667 0.000000
+v -5.000000 5.000000 0.000000
+v -1.666667 -5.000000 0.000000
+v -1.666667 -1.666667 0.000000
+v -1.666667 1.666667 0.000000
+v -1.666667 5.000000 0.000000
+v 1.666667 -5.000000 0.000000
+v 1.666667 -1.666667 0.000000
+v 1.666667 1.666667 0.000000
+v 1.666667 5.000000 0.000000
+v 5.000000 -5.000000 0.000000
+v 5.000000 -1.666667 0.000000
+v 5.000000 1.666667 0.000000
+v 5.000000 5.000000 0.000000
+# 16 vertices
+cstype bezier
+deg 3 3
+# Example of line continuation
+surf 0.000000 1.000000 0.000000 1.000000 13 14 \
+                 15 16 9 10 11 12 5 6 7 8 1 2 3 4
+parm u 0.000000 1.000000
+parm v 0.000000 1.000000
+end
+# 1 element
+
+Cardinal Curve
+
+# 3.0 Cardinal curve
+v 0.940000 1.340000 0.000000
+v -0.670000 0.820000 0.000000
+v -0.770000 -0.940000 0.000000
+v 1.030000 -1.350000 0.000000
+v 3.070000 -1.310000 0.000000
+# 6 vertices
+cstype cardinal
+deg 3
+curv 0.000000 3.000000 1 2 3 4 5 6
+parm u 0.000000 1.000000 2.000000 3.000000 end
+# 1 element
+
+Texture-Mapped Square
+
+# A 2 x 2 square mapped with a 1 x 1 square
+# texture stretched to fit the square exactly.
+mtllib master.mtl
+v  0.000000 2.000000 0.000000
+v  0.000000 0.000000 0.000000
+v  2.000000 0.000000 0.000000
+v  2.000000 2.000000 0.000000
+vt 0.000000 1.000000 0.000000
+vt 0.000000 0.000000 0.000000
+vt 1.000000 0.000000 0.000000
+vt 1.000000 1.000000 0.000000
+# 4 vertices
+usemtl wood
+# The first number is the point,
+# then the slash,
+# and the second is the texture point
+f 1/1 2/2 3/3 4/4
+# 1 element
+
+For Further Information
+
+For further information about the Wavefront OBJ format, see the specification.
+
+You can also contact:
+
+Wavefront Technologies
+530 East Montecito Street
+Santa Barbara, CA 93103
+Voice: 805-962-8117
+FAX: 805-963-0410
+WWW: http://www.aw.sgi.com/
+
+Wavefront also maintains a toll-free support number and a BBS for its
+customers. There are many Wavefront user groups, too.
+
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