Hello,
I guess this is more a usage question, I've never tried what I'm doing
now and don't really know if I'm doing it the right way.
I want to use vertex attributes in a GLSL vertex shader. Now, here is
roughly the sequence of events I'm doing. I would appreciate if
someone could tell me if it's wrong or missing something. (note: I
checked osgFX/BumpMapping since it uses vertex attributes, but
couldn't find anything I'm doing radically different - plus it doesn't
use GLSL so that's one part I can't check)
1. I load my vertex and fragment shaders and assign them to an
osg::Program, and also give a name to the vertex attribute slot I want
to use:
// createShaders just loads shaders named name.vert and name.frag
osg::ref_ptr<osg::Program> program = createShaders("shader_name");
program->addBindAttribLocation("color_value", 6);
loadedModel->getOrCreateStateSet()->setAttribute(program.get());
2. Then I generate my vertex attribute array. For now I'm just testing
by creating a Vec4Array and setting all Vec4f's to red.
for (... each geode in my model ...)
{
for (... each geometry in my model ...)
{
const osg::Array* vertices = object->getVertexArray();
osg::ref_ptr<osg::Vec4Array> colors =
new osg::Vec4Array(normals->getDataSize());
osg::Vec4f* colorData = (osg::Vec4f*)colors->getDataPointer();
for (unsigned int n = 0;
n < (unsigned int)vertices->getDataSize(); ++n)
{
colorData[n] = osg::Vec4f(0.0f, 1.0f, 0.0f, 1.0f);
}
// Set the computed colors as vertex attributes (attribute slot 6)
object->setVertexAttribData(6,
osg::Geometry::ArrayData(colors.get(),
osg::Geometry::BIND_PER_VERTEX, GL_FALSE));
}
}
3. My vertex shader "shader_name.vert" looks roughly like this:
attribute vec4 color_value;
varying vec3 DiffuseColor;
void main()
{
DiffuseColor = color_value.rgb;
gl_Position = ftransform();
}
And my fragment shader "shader_name.frag", unsurprisingly:
varying vec3 DiffuseColor;
void main()
{
gl_FragColor = vec4(DiffuseColor, 1.0);
}
So my objects should be constant green, but they are constant black...
:-( If I change either the fragment shader or vertex shader to
hard-code a color, that works fine, but it just seems that my vertex
attributes aren't getting through (or they are but they're all zero,
which they shouldn't be considering the code above I think).
I'm sure I'm missing something, but what? Thanks in advance,
J-S
--
______________________________________________________
Jean-Sebastien Guay [EMAIL PROTECTED]
http://whitestar02.webhop.org/
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