Martin Scheffler wrote:
Hi,
I use 3ds Max render-to-texture to generate ambient occlusion maps.
I then export the model to collada (with the nextgen plugin) and try to load them into osg.
For some meshes I get this message: "Ambient occlusion map only supported when diffuse texture also specified", and the occlusion map is not loaded.
Is that a collada thing or a shortcoming of the osg collada importer?
Can I circumvent it by adding small one-color textures to the no-texture materials? Or is there a better way?
Thank you.
-
Martin,
It is the way the Collada importer is written. I admit that I thought I
had good reason for making it work that way when I wrote that bit,
however, now, I cannot remember what that reason was!
It was something to do with mapping the Collada Common profile, which
is supposed to represent a fixed a function pipeline, on to the OpenGL
fixed function pipeline.
This is what the code does when both the diffuse and ambient texture
maps are present.
// Set the ambient and diffuse colour white so that the
incoming fragment colour ends up as a
// lit white colour. I modulate both textures onto this
to approximate the lighting equation.
// Using a zero diffuse and then an ADD of the diffuse
texture seems overlit to me.
mat->setAmbient( osg::Material::FRONT_AND_BACK,
osg::Vec4( 1.0f, 1.0f, 1.0f, 1.0f ) );
mat->setDiffuse( osg::Material::FRONT_AND_BACK,
osg::Vec4( 1.0f, 1.0f, 1.0f, 1.0f ) );
// Use the ambient texture map as an occlusion map.
ss->setTextureMode( AMBIENT_OCCLUSION_UNIT,
GL_TEXTURE_2D, GL_TRUE );
ss->setTextureAttribute(AMBIENT_OCCLUSION_UNIT, new
osg::TexEnv(osg::TexEnv::MODULATE) );
ss->setTextureAttribute( AMBIENT_OCCLUSION_UNIT,
AmbientStateAttribute );
// Modulate in the diffuse texture
ss->setTextureMode( MAIN_TEXTURE_UNIT,
GL_TEXTURE_2D, GL_TRUE );
ss->setTextureAttribute(MAIN_TEXTURE_UNIT, new
osg::TexEnv(osg::TexEnv::MODULATE) );
ss->setTextureAttribute( MAIN_TEXTURE_UNIT,
DiffuseStateAttribute );
So setting up a texture for your diffuse colour should probably work.
Roger
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