Hi Robert,
When writing a tesselation shader, you have to decide the patch size you want
to be used as input by this shader.
I mean that your code for 3-vertices patch will be really different from a code
for doing the same thing with 4-vertices patch.
So, I think the idea "GL_PATCH_SIZE is associated with the program" is not a
bad idea, since they are really correlated.
The idea of a StateAttribute could lead to better optimization (less openGL
call to set alwas the same GL_PATCH_SIZE value) but I don't think that's a good
idea because it can be hard to always know which GL_PATCH_SIZE value will be
used for a particular shader.
Maybe another idea should be to exend the osg::PrimitiveSet::Mode enum like
that : (so all CPU code, like visitors know how to iterate over the data)
Code:
{
POINTS
LINES
LINE_STRIP
LINE_LOOP
TRIANGLES
TRIANGLE_STRIP
TRIANGLE_FAN
QUADS
QUAD_STRIP
POLYGON
LINES_ADJACENCY
LINE_STRIP_ADJACENCY
TRIANGLES_ADJACENCY
TRIANGLE_STRIP_ADJACENCY
PATCHES_1 // GL_PATCH - Patch
size = 1
PATCHES_2 // GL_PATCH - Patch
size = 2
PATCHES_3 // GL_PATCH - Patch
size = 3
...
PATCHES_N // GL_PATCH - Patch
size = N
};
Thank you!
Cheers,
Aurelien
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=54490#54490
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