From 6f8fc2ca99d1943977697920940d4bcadaef0374 Mon Sep 17 00:00:00 2001
From: Joe Crayne <joe@jerkface.net>
Date: Tue, 23 Jul 2019 02:14:49 -0400
Subject: Fancier specular lighting.

---
 hello_obj2.lc | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/hello_obj2.lc b/hello_obj2.lc
index a6df7b7..00ba27c 100644
--- a/hello_obj2.lc
+++ b/hello_obj2.lc
@@ -46,6 +46,9 @@ ambientOnly cam color texture prims = prims
 -- The illum 0 can be implemented using illum 1 code by setting
 --   KaIa = Kd
 --   Ij = 0 forall j
+--
+-- The spec seems to require settings for Ia and Ij (j = light number).
+-- Ka should probably be calculated similar to Kd: using a Ka_map texture.
 lambertianReflectance cam lightpos color texture prims = prims
     & mapPrimitives (\(p,n,uvw) ->
         let light_vector = normalize $ -- light direction from surface
@@ -78,17 +81,21 @@ blinnPhong cam lightpos color texture specular prims = prims
                             if lightpos%w == 0
                                 then lightpos%xyz
                                 else homoproj lightpos - homoproj p
-            campos = cam *. V4 0 0 0 1
-            view_vector = normalize $ homoproj campos - homoproj p
-            h = normalize $ light_vector + view_vector
-            refl = dot h (normalize n)
             lambertian = dot light_vector (normalize n)
-          in ( coordmap cam p, V2 uvw%x (1 - uvw%y), lambertian, refl ))
-    & rasterizePrimitives (TriangleCtx CullBack PolygonFill NoOffset LastVertex) (Smooth,Smooth,Smooth)
-    & mapFragments (\(uv,lambertian, refl) ->
+          in ( coordmap cam p, V2 uvw%x (1 - uvw%y), lambertian, n, p ))
+    & rasterizePrimitives (TriangleCtx CullBack PolygonFill NoOffset LastVertex) (Smooth,Smooth,Smooth,Smooth)
+    & mapFragments (\(uv,lambertian, n, p) ->
         let ct = texture2D (Sampler PointFilter MirroredRepeat texture) uv
             ns = specular%w
             ks = point $ specular%xyz
+            campos = cam *. V4 0 0 0 1
+            view_vector = normalize $ homoproj campos - homoproj p
+            h = normalize $ light_vector + view_vector
+            refl = dot h (normalize n)
+            light_vector = normalize $ -- light direction from surface
+                            if lightpos%w == 0
+                                then lightpos%xyz
+                                else homoproj lightpos - homoproj p
         in (( color * ct *! (0.5 + 0.5*lambertian) + if refl>0 then ks *! pow refl ns else zero )) )
     & accumulateWith (DepthOp Less True, ColorOp NoBlending (V4 True True True True))
 
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