Basing on this post, I was trying to figure out how to use VBO's in Haskell. I tried to fill in the bits that were not covered there:
data Sprite = Sprite { spriteImage :: Image
, spritePosition :: Position
} deriving (Show, Eq)
spriteBatch :: [Sprite] -> [(TextureObject, [Sprite])]
spriteBatch = (map f) . toList . (groupedBy (imageTexture . spriteImage))
where f (t, s) = (t, s)
offset = plusPtr nullPtr
renderSprites :: [Sprite] -> IO ()
renderSprites l = (flip mapM_) (spriteBatch l) $ \(t, sps) -> do
textureBinding Texture2D $= Just t
let l = concat $ map sprToList sps
vbo <- vboOfList ((length l)*4) l
displayVbo vbo $ fromIntegral $ length sps
where
sprToList :: Sprite -> [GLfloat]
sprToList (Sprite (Image _ (TexCoord2 u0 v0) (TexCoord2 u1 v1) (Size w h) _) (Position x y)) =
[fromIntegral x, fromIntegral y, u0, v0
,fromIntegral (x+w), fromIntegral y, u1, v0
,fromIntegral (x+w), fromIntegral (y+h), u1, v1
,fromIntegral x, fromIntegral (y+h), u0, v1
]
vboOfList :: Int -> [GLfloat] -> IO BufferObject
vboOfList size elems = do
let ptrsize = toEnum $ size * 4
arrayType = ElementArrayBuffer
(array:_) <- genObjectNames 1
bindBuffer arrayType $= Just array
arr <- newListArray (0, size - 1) elems
withStorableArray arr $ \ptr -> bufferData arrayType $= (ptrsize, ptr, StaticDraw)
bindBuffer ArrayBuffer $= Nothing
return array
displayVbo buff size = do
let stride = 2*(2*4)
vxDesc = VertexArrayDescriptor 2 Float stride $ offset 0
texCoo = VertexArrayDescriptor 2 Float stride $ offset 8
bindBuffer ArrayBuffer $= Just buff
arrayPointer VertexArray $= vxDesc
arrayPointer TextureCoordArray $= texCoo
clientState VertexArray $= Enabled
clientState TextureCoordArray $= Enabled
drawArrays Quads 0 size
bindBuffer ArrayBuffer $= Nothing
You can find the full code here, in case you need to.
On the master branch, the very same function uses normal vertex calls to draw the Sprites and it works perfectly. But using VBO's, the sprite just isn't there; I get a blank screen.
Can anyone explain to me what I did wrong here?
