Replying to myself with what I have managed to figure out so far to provide some information in case it comes up in a search. I can't vouch for the accuracy as this is still new to me. Anyway:
- Compile messages end up being sent through the osg::NotifyHandler mechanism.
- Shaders don't appear to be compiled immediately, but if you use them (by attaching an osg::Program to a osg::StateSet with setAttributeAndModes()), they end up being compiled and used at a later point.
- osg::StateSet::addUniform() with a osg::Uniform argument seems to be the way to specify uniforms.
- osg::Program::addBindAttribLocation() is a means of binding variables to a specific attribute index (output location), which you need for other calls. I believe location layout qualifiers in the shaders themselves can be used as well.
- osg::Program::getAttribBindingList() seems to only return the variables set with addBindAttribLocation(), and not ones specified in the shader itself. This might be a timing issue, perhaps the results change after the shaders are actually compiled and linked?
- osg::State::setUseModelViewAndProjectUniforms(true) can be used to automatically hook up variables such as "osg_ModelViewProjectionMatrix", which seems to be an OSG analogue to "gl_ModelViewProjectionMatrix". This seems to be a useful bridge while trying to figure things out.
- The compile messages can be used to confirm the actual attribute indexes used.
- Variables that aren't used may be optimised out, which makes them unavailable.
- Using Geometry::setVertexAttribArray with the last argument set correctly (eg. BIND_PER_VERTEX) seems to be the way that you can pass texture coordinates to shaders. I'm guessing other information such as vertices and normals are handled similarly.
Hopefully this helps someone in a similar situation to the one I was in. On 23/09/15 22:14, Garth D wrote:
Hi all, I was wondering if anyone can make some suggestions as to resources that are useful for learning GLSL in modern OpenGL (say, 3.0+) with a specific focus on use with OSG. My existing GLSL knowledge is weak compared to my general 3D knowledge, and mostly dates back to the early days of shaders. A lot of what I have personally done with OpenGL and OSG has involved the fixed-function pipeline, or things that map to it fairly closely. Thus far I've been digging around online for GLSL resources, but tend to frequently find myself doing it the wrong way as I'm using features that have since become deprecated. On the OSG side I tend to dig around in the OSG examples and search the source to try to find the OSG equivalents to OpenGL calls I see mentioned in the GLSL resources. I then put these together and if I'm lucky something useful comes out. :) I think I'll figure things out eventually if I continue to crash around blindly as I have been, but if anyone can suggest some better starting points for GLSL use in OSG specifically, it would be much appreciated. :) Cheers, Garth _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
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