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bobmckenzie123

OpenGL Hardware Skinning + GLSL + COLLADA + VBO

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bobmckenzie123    100
Hi,

I'm developing an application using C# and the Tao framework. The application currently loads a COLLADA file, exported from DAZ Studio, with a skeletal character/mesh with animations. Using Tao I've been able to render the skeleton and animate it, but only using the Fixed Functionality of OpenGL. Now I want to render the actual skin/mesh and this is where I"m having some issues. I have been able to load the vertexes and indexes into VBO's and I'm rendering the 'PolyLists' using glDrawElements. Currently I just get a big deformed blob of quads and I know that I have to implement a vertex shader that implements the skinning formula defined in the COLLADA spec. This is the first time I've played with shaders. I've implemented a basic shader that successfully adds 100 to the Y coordinated of the vertex, and it works because the blob and the skeleton both get rendered higher than when the shader is not active.

Here's my problem. My model has 67619 vertices, normals and uv coords. This is okay because I'm putting them into VBO's. However, I've also got an array of weights with 51738 floats as well as other arrays of uint's that keep track of how many joints influence each vertex etc. How do I pass these arrays into my shader? I thought about putting them into VBO's but I have no idea how to access vbo's in 'raw data' form so that I can index into them any way I want from within the shader. I started playing around with declaring uniform arrays in my shader but when declared a float array with 10000 elements (just as a test), my app completely froze. Can anyone give me some direction on how to best approach this?

Thanks,

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karwosts    840
You can declare arbitrary data as an attribute input similar to how you would for a postition, normal, or texcoord.
Take a look at these functions, they should get you on the right track:

[url="http://www.opengl.org/sdk/docs/man/xhtml/glGetAttribLocation.xml"]glGetAttribLocation[/url]
[url="http://www.opengl.org/sdk/docs/man/xhtml/glVertexAttribPointer.xml"]glVertexAttribPointer[/url]
[url="http://www.opengl.org/sdk/docs/man/xhtml/glEnableVertexAttribArray.xml"]glEnableVertexAttribArray[/url]

Also a heads up if you want to send integers as an attribute instead of floats, you need to use glVertexAttribIPointer instead. You'll probably need this for skinning to do matrix index selection.

You can't access VBO's as 'raw data' in the shader similar to how you can access an array, but using these functions you can attach additional data to each vertex that will be supplied as an input attribute.

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bobmckenzie123    100
Thank you very much karwosts. From quickly googling those function they look like what I need. I had no clue that the glVertexPointer, glNormalPointer were/are deprecated. I will change my code and see if I can get my app working with these functions.

Thanks,

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