render modelViewProj = let
  emptyFB           = FrameBuffer (depthImage1 1000.0)
  rasterCtx         = LineCtx 1.0 LastVertex
  fragmentCtx       = accumulationContext (DepthOp Less False)
  vertexShader v    = (v, v)
  vertexStream      = fetch "stream4" Line (Attribute "position4" :: Vec 4 Float)
  primitiveStream   = mapPrimitives vertexShader vertexStream
  fragmentStream    = rasterizePrimitives rasterCtx Flat primitiveStream
  fragmentShader    = \v -> ()
  frame             = accumulate fragmentCtx fragmentShader fragmentStream emptyFB
 in ScreenOut frame

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