makeFrame (time :: Float)
          (vertexstream :: PrimitiveStream Triangle ((Vec 4 Float)))

          = imageFrame (emptyDepthImage 1, emptyColorImage navy)
  `overlay` fragments
  where
    projmat = perspective 0.1 100.0 (30 * pi / 180) 1.0
          .*. lookat (V3 3.0 1.3 0.3) (V3 0.0 0.0 0.0) (V3 0.0 1.0 0.0)
          .*. rotMatrixY (pi / 24.0 * time)

    fragments =
          vertexstream
        & mapPrimitives (\((x)) -> (scale 0.5 (projmat *. x), x))
        & rasterizePrimitives (TriangleCtx CullNone PolygonFill NoOffset LastVertex) ((Smooth))
        & accumulateWith (DepthOp Less True, ColorOp NoBlending (V4 True True True True))

main = renderFrame $
   makeFrame (Uniform "Time")
             (fetch "stream4" ((Attribute "position4")))