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I've written plenty of 

#version 330 core

GLSL shaders I'd like to reuse along with the OpenSceneGraph (OSG) 3.2.0 framework, and try to figure out how to get the state from the OSG I need to pass in by uniforms, and how to set them without having to change well-tested shader code, as well as how to populate arbitrarily named attributes.

This (version 140, OpenGL 3.1) http://trac.openscenegraph.org/projects/osg/browser/OpenSceneGraph/trunk/examples/osgsimplegl3/osgsimplegl3.cpp

and this (version 400) http://trac.openscenegraph.org/projects/osg/browser/OpenSceneGraph/trunk/examples/osgtessellationshaders/osgtessellationshaders.cpp

example give rise to a notion of aliasing certain attribute and uniform names to "osg_", but I'd like to use arbitrary names for the uniforms, 

uniform mat4 uMVMatrix;
/*...*/

and to refer, or let the OSG refer, to the attributes by their numbers only, so sth like this

/*...*/
layout(location = 0) in vec4 aPosition;
layout(location = 1) in vec3 aNormal;
layout(location = 2) in vec2 aST;

as used in my legacy shaders, I'd like the OSG framework to populate with the vbo it already maintains for the "Drawables", or, at least, use an API call and do it myself.

I addition, I'd like to populate uniforms for lights and shawdowmaps by means of the scenegraph and the visitors; "somewhere" and "somehow" in the SG there must be light and esp shadow information be aggregated for default shading, so I'd like simply like to use this data and tailor it to fit to my custom shaders.

So the fundamental question is

How to populate arbitrary GLSL 330 shaders with data from within OSG without having to resent to redundant uniform assignment - providing my "u[..]Matrix" manually in addition to the "osg_[...]" uniform set by OSG - or changing attribute names in the shader sources?

Solkar
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1 Answers1

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I just stumbled upon this, turns out, you can just use your own names after all, if you just specify the layout location (so far I only tried it for the vertex position, so you might have to take care of using the correct layout location as osg would specify them, i.e. vertex position at 0, normal at 1 (which is not done the example of the link though))

layout (location = 0) in vec3 vertex;

this is enough to use the variable named vertex in the shader.

The link also provides an example to use custom names for matrices: you create an osg::Uniform::Callback class that uploads the matrix to the uniform. when you create the osg::Uniform object, you specify the name of your choosing and add the callback.

Tare
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