On 03/12/2012 10:04 AM, Ethan Fahy wrote:
Thanks Jason,
I understand about the interpolation. I have been operating under the
assumption that if I use a node visitor to loop over each primitive in my
object, create a floatArray of index numbers of size=size(primitive array), and
then bind_per_primitive, then I shouldn't have to worry about interpolation of
those index numbers within the shader. Is that correct?
If you're trying to get the same value for all fragments on a primitive,
then yes, this will work. Be aware, though, that rendering geometry
with per-primitive binding is going to be quite slow compared to overall
or per-vertex binding.
As an alternative, you could specify your floatArray at
size=size(primitive array) * 3 (assuming you're rendering triangles) and
just specify the same index for all three vertices of each triangle.
Then, you could use per-vertex binding and not fall off the fast path.
I noticed that in Christian's code snippet that the osg::Program that he
created was not attached to the geometry's stateset. Without attaching it, you
will still have a floatArray stored in the 6 position, but it will not have a
name and therefore I don't think you can access it from the shader.
In either case, when i try to add my floatArray to the 6th vertex attribute, my
shaders stop working. I don't get any glsl errors printed to screen, but even
if I try to do something simple like assign all color values to black, the
shader just spits out the underlying object colors and ignores my shader
commands. If I don't attach the osg::Program to my object's stateset, the
shader commands do work again but I can't access my 6th vertex attribute
because it wasn't named.
Here is the stateset that was added to my object.obj's geometry:
StateSet {
rendering_hint DEFAULT_BIN
renderBinMode INHERIT
Program {
name "targetIndices"
GeometryVerticesOut 1
GeometryInputType TRIANGLES
GeometryOutputType TRIANGLE_STRIP
AttribBindingLocation indices 6
num_shaders 0
}
}
I'm assuming most of these things are default values since I never specified
GeometryVerticesOut, GeometryInputType, GeometryOutputType, or num_shaders when
I created my osg::Program. Are these defaults the cause of my problems?
The defaults are probably fine (they apply to geometry shaders, which I
don't think you're using). The attribute binding for "indices" at
attribute 6 looks good as well. However, it looks as if there are not
any shaders attached to your Program ("num_shaders 0"), which isn't
going to work at all. You need to create an osg::Shader (specifying the
type of shader, vertex, geometry, or fragment), add the shader's source
to it, and then add the shader to the Program. Then, you can attach the
program to the StateSet and everything should work:
shader = new osg::Shader(osg::Shader::FRAGMENT);
shader->setShaderSource(source);
program->addShader(shader);
--"J"
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