Userdefined vertexdata for realtimeshaders?

[André Adam <a_adam(at)49games.de>]

Heya, perhaps someone who has done this before can help out one of our 
programmers?

Thanks in advance for any hint, cheers!

   -André

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Hi!

I'm in the middle of writing a realtimeshader (OpenGL (2.0)) and 
currently lighting via normalmaps is implemented.

For correct interpretation of the normals in the normalmap you need some 
extrainformation (the tangent to compute the tangentspacetransformation) 
per vertex.

Currently we compute the tangent on the fly before passing the data to 
OpenGL because the "XSI_RTS_TriangulatedGeometry" (see below) doesn't 
leave space for userdata.
This has two drawbacks:
1. Every frame we compute data which doesn't change if the geometry 
doesn't change.
2. The result contains artefacts because we can't "smooth" the data 
since we'd need to find all adjacent triangles of a vertex to do so. 
(And this is to expensive to do on trianglelists!)


The solution could be some preprocessing of the geometry in XSI and then 
let XSI pass this preprocessed data along with the positions, normals, 
colors and texcoords to the realtimeshader.
Unfortunately the only way we saw was a normalmapping-implementation 
which stores the extradata needed in the vertexcolor values. 
Unfortunately we need the vertexcolors for other purposes - like 
coloring the object... :)

Is it somehow possible to pass userdefined vertexdata to a realtimeshader?


Thanks in advance!

Bjoern Gdanietz

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(From XSISDK 5.11)

typedef struct tagXSI_RTS_TriangulatedGeometry
{
 // Triangle lists information
 ULONG         m_Type;
 ULONG         m_lNbTriangleLists; //! Number of triangle lists
 XSI_RTS_TriangleList *m_pTriangleLists; //! Triangle lists
 ULONG         m_NbVertices;  //! Total number of vertices
 // Pointer streams
 XSI_RTS_Vector3d **m_pPositionDPtrArray; //! Array of pointers to the 
positions (DOUBLE)
 XSI_RTS_Vector3 **m_pPositionPtrArray; //! Array of pointers to the 
positions
 XSI_RTS_Vector3 **m_pNormalPtrArray; //! Array of pointers to the normals
 XSI_RTS_ColorRGBA **m_pColorPtrArray; //! Array of pointers to the 
colors   XSI_RTS_Vector2 **m_pTexCoordPtrArray; //! Array of pointers to 
the texture
 // Vertex attribute arrays streams
 ULONG         m_NbUniqueVertices; //! Total number of unique vertices
 XSI_RTS_Vector3 *m_pPositionArray; //! Array of positions
 XSI_RTS_Vector3 *m_pNormalArray; //! Array of normals (interleaved by 
streams)
 XSI_RTS_ColorRGBA *m_pColorArray; //! Array of colors (interleaved by 
streams)

 XSI_RTS_Vector2 *m_pTexCoordArray; //! Array of texture coordinates
 ULONG         *m_pIndices;   //! Array of global indices

 // Number of normals, colors and texture coordinates
 ULONG         m_lNbNormalStreams; //! Number of normal streams
 ULONG         m_lNbColorStreams; //! Number of color streams
 ULONG         m_lNbTexCoordStreams; //! Number of texture coordinates 
streams

} XSI_RTS_TriangulatedGeometry;






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