Hi! Profiling says that my program spends 18.4 % of time (that is around three seconds) and 18.3 % of allocations in this function which is saving the rendered image to a PPM file: saveImageList :: String -> Int -> Int -> [ViewportDotColor] -> IO () saveImageList filename width height image = do B.writeFile filename file where file = B.append header bytes header = C.pack $ "P6\n" ++ show width ++ " " ++ show height ++ "\n255\n" bytes = B.pack $ concatMap (color . dealpha . (\(ViewportDotColor _ c) -> c)) image where color (VoxelColor red green blue _) = [floor $ red * 255, floor $ green * 255, floor $ blue * 255] dealpha c = addColor c (VoxelColor 1.0 1.0 1.0 1.0) -- white background For a 921615 bytes large file to save this is too much in my opinion. And I think that it consumes to much allocations. Probably it should not store intermediate lists? Any suggestions? Best regards Mitar