render modelViewProj = let
  emptyFB           = FrameBuffer (colorImage1 (V4 0.5 0.0 0.4 1.0))
  rasterCtx         = LineCtx 1.0 LastVertex
  fragmentCtx       = accumulationContext (ColorOp NoBlending (V4 True True True True))
  vertexShader v    = (PrimMulMatVec modelViewProj v, v)
  vertexStream      = fetch "stream4" Line (Attribute "position4" :: Vec 4 Float)
  primitiveStream   = mapPrimitives vertexShader vertexStream
  fragmentStream    = rasterizePrimitives rasterCtx Flat primitiveStream
  fragmentShader =  \f -> f
  frame             = accumulate fragmentCtx  fragmentShader fragmentStream emptyFB
 in ScreenOut frame

main = render (Uniform "MVP" :: Mat 4 4 Float)