Question

基于this post，我试图弄清楚如何在Haskell中使用VBO。我试着填写那里没有的位：

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

如果需要，您可以找到完整的代码here。

在master branch上，同一个函数使用普通的vertex调用来绘制Sprites，它完美无缺。但是使用VBO，精灵就不在那里;我得到一个空白的屏幕。

有谁可以向我解释我在这里做错了什么？

Answer 1

你正在为顶点和uv使用一个缓冲区。使用两个缓冲区，一个用于顶点，一个用于uvs。

Haskell中的OpenGL VBO

1 个答案: