[osg-users] How to access material properties from a GLSL shader?

[Armin Samii]

Thanks, Chris. Those materials are not available post-GLES 1.2, and I
couldn't find anywhere in the OSG codebase that exposed materials as
uniforms. I did find this:
https://github.com/gwaldron/osgearth/blob/master/src/osgEarth/Lighting.cpp

Which traverses the scene graph, finds Materials, and replaces them with
Uniforms. I think that's a reasonable solution.

- Armin

On Wed, Jan 8, 2020 at 6:21 PM Chris Djali / AnyOldName3 <
krizdjali at gmail.com> wrote:

> Hi,
>
> osg::Material pretty much encapsulates OpenGL's fixed-function material
> state, so things like glMaterialfv (that controls material settings for
> whole draw calls) and glColorMaterial (that controls what vertex colours
> actually affect). If you're using a suitably old GLSL version, you can
> access this state through the built-in uniforms. These aren't featured
> prominently in lots of the modern OpenGL documentation like the wiki as
> they're removed in modern OpenGL, but I have this bookmarked and it at
> least says what's there: http://mew.cx/glsl_quickref.pdf. Once you know
> an actual uniform name, relevant stuff should show up in a search engine.
> The one problem you'll hit is that there's no built-in uniform to say
> whether glColorMaterial is enabled or what mode it's in, so you'll have to
> set that up yourself with a uniform or shader define.
>
> I *think* that with the right combination of settings, OSG exposes
> similar uniforms in newer OpenGL/GLSL versions where the fixed function
> pipeline has been removed, so that's something to look into. I've never
> needed this, though, so don't know if it just happens when OSG is compiled
> with GL3 support, or whether there's more that you need to do.
>
> Hope this helps,
>
> Chris
>
> On Wednesday, 8 January 2020 22:53:28 UTC, Armin Samii wrote:
>>
>> Does openscenegraph provide easy access to osg::Material values in the
>> shaders? If so, in which Uniforms are the various properties set? If not,
>> is the best path forward to set my own Uniforms based on osg::Material?
>>
>> For context: I had an OBJ/MTL that loaded and rendered fine by default,
>> but when I turn on `setUseVertexAttributeAliasing`, the texture coordinates
>> seem to break. I am trying to replace the default rendering with my own
>> shader instead, but can't reproduce the original look and feel. While
>> texture coordinates and texture loading does work with shaders, I cannot
>> seem to find how to access the colors specified in the MTL files.
>>
>> (A google search shows several results for "openscenegraph material
>> shaders" which looks helpful, but they are all in the forum, which is now
>> inaccessible. Apologies if this question has been asked and answered
>> elsewhere.)
>>
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