tetrahedron = map (\v -> V4 v%x v%y v%z 1)
    [ V3 0 0 0, V3 1 0 0, V3 0 1 0
    , V3 1 0 0, V3 0 1 0, V3 0 0 1
    , V3 0 1 0, V3 0 0 1, V3 0 0 0
    , V3 0 0 1, V3 0 0 0, V3 0 0 1
    ]

f x = (x + sin x + sin (1.1 * x)) `mod` 4 * 2

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

    =         imageFrame (emptyDepthImage 1, emptyColorImage navy)
    `overlay` accumulablefragments
  where
    accumulablefragments
        = vertexstream
        & mapPrimitives (\x -> (scale 0.5 (projmat *. x), x))
        & rasterizePrimitives (TriangleCtx CullNone PolygonFill NoOffset LastVertex) Smooth
        & filterFragments (\x -> True)
        & mapFragments (\x -> (rotMatrixZ time *. rotMatrixY time *. x) *! f time)
        & accumulateWith (DepthOp Less True, ColorOp NoBlending (V4 True True True True))

main = renderFrame $
   makeFrame (Uniform "Time")
             (Uniform "MVP")
             (fetchArrays Triangle tetrahedron)