Hi all,
I want to use pseudo-instancing
(http://developer.download.nvidia.com/SDK/9.5/Samples/DEMOS/OpenGL/src/glsl_pseudo_instancing/docs/glsl_pseudo_instancing.pdf)
in OpenSG. Basically, I would like to render thousands of identical
meshes with different vertex attributes, let's say multitexture
coordinates. A vertex shader is used to translate the texture
coordinates into transformations and therefore influences the
positioning of the different instances. I have implemented a memory
consuming approach, where each instance is represented by a geometry
core as a leaf in the scenegraph with corresponding texture coordinates.
Unfortunately, the texture coordinates are duplicated for each vertex of
the geometry core and, in addition, each vbo is transfered to the
graphics hardware. Basically, just the texture coordinates and one
instance of the geometry should be considered.
In OpenGL, this implementation would look like this (ref. Nvidia's
pseudo-instancing):
// Render the instances of the mesh
for(i=0; i<instances.size(); i++)
{
// Send down the matrix and other parameters
// pseudo-instancing passes per-instance data down
// as texture coordinates
glMultiTexCoord4fv(GL_TEXTURE1, instances[i].mWorld[0]);
glMultiTexCoord4fv(GL_TEXTURE2, instances[i].mWorld[1]);
glMultiTexCoord4fv(GL_TEXTURE3, instances[i].mWorld[2]);
// Set the color for the instance
glColor4fv(gInstances[i].mColor);
// Render the instance
mesh->render();
}
Has anybody faced that problem before and implemented a node core, which
is able to handle these features? I would imagine that some multifields
for texture coordinates and a field for handling the geometry, let say a
GeometryPtr, are needed. Can anybody help me realizing this node core?
Thanks a lot!
Daniel
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