-- works with type signature
--frag :: (Vec 4 Float,Vec 2 Float) -> Vec 4 Float
frag = \(x,uv) -> x

makeFrame (vertexstream :: PrimitiveStream Triangle (Vec 4 Float,Vec 2 Float))

          = imageFrame (emptyDepthImage 1, emptyColorImage navy)
  `overlay` fragments
  where
    fragments =
          vertexstream
        & mapPrimitives (\(x,uv) -> (x,x,uv))
        & rasterizePrimitives (TriangleCtx CullNone PolygonFill NoOffset LastVertex) (Smooth,Smooth)
        & mapFragments frag
        & accumulateWith (DepthOp Less True, ColorOp NoBlending (V4 True True True True))

main = renderFrame $
   makeFrame (fetch "stream4" (Attribute "position4",Attribute "vertexUV"))