Re: [Haskell-cafe] OpenGL's VBO with Haskell

Oh, and you might try this using Vertex Arrays instead of VBOs. I'll also assume you're checking for the appropriate ARB extensions to make sure VBOs are available on your hardware... If this displays correctly using Vertex Arrays (which can still be interleaved), then I would check your hardware if I were you. On Mon, Aug 25, 2008 at 2:35 PM, Jefferson Heard wrote:

That code looks like it ought to work, and I assume if you're using VBOs that you know how to make sure your frustum is setup so that you're object's visible. Are you running this in Windows or in Linux or ? and what version of GHC are you using?

There is also a specific HOpenGL mailinglist, just called HOpenGL that you can join by searching for it on the http://haskell.org site.

On Mon, Aug 25, 2008 at 1:43 PM, Twinside wrote:

...

Hi Haskell list,

Today I'm turning to you for the use of VBO (Vertex Buffer Object) in Haskell. I seem to be able to create one without any problem using the following code :

------------------------------------------------------ vboOfList :: Int -> [Float] -> IO BufferObject vboOfList size elems = let ptrsize = toEnum $ size * 4 arrayType = ElementArrayBuffer in do [array] <- genObjectNames 1 bindBuffer arrayType $= Just array arr <- newListArray (0, size - 1) elems withStorableArray arr (\ptr -> bufferData arrayType $= (ptrsize, ptr, StaticDraw)) bindBuffer ArrayBuffer $= Nothing reportErrors return array ------------------------------------------------------

However the problem arise when I try to draw primitives using this vbo :

------------------------------------------------------ displayVbo buff size = do let stride = toEnum sizeOfVertexInfo vxDesc = VertexArrayDescriptor 3 Float stride $ offset 0 colors = VertexArrayDescriptor 4 Float stride $ offset 12 texCoo = VertexArrayDescriptor 2 Float stride $ offset (12 + 16) filt = VertexArrayDescriptor 4 Float stride $ offset (12 + 16 + 8) bindBuffer ArrayBuffer $= Just buff

arrayPointer VertexArray $= vxDesc arrayPointer ColorArray $= colors arrayPointer TextureCoordArray $= texCoo arrayPointer SecondaryColorArray $= filt

drawArrays Quads 0 size bindBuffer ArrayBuffer $= Nothing ------------------------------------------------------

Nothing is displayed on screen.

As you can see, my VBO contain interleaved data : - 3 float for the vertex - 4 for the color - 2 for the texture coordinate - 4 for the secondary color)

The 'offset' function has type Int -> Ptr Float, and is used to forge a pointer from an Int, to mimic the C way of using VBO. As far as I've checked, the values in my list for VBO generation are valid and well displayed using other techniques.

So is there a workaround other method for my solution, preferably by keeping my data interleaved? Secondly, is there any sample for advanced features like VBOs in Haskell?

Regards, Vincent

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-- I try to take things like a crow; war and chaos don't always ruin a picnic, they just mean you have to be careful what you swallow. -- Jessica Edwards