[osg-users] How to update uniform not continually

[Nan WANG]

Hello:

I am wondering about how to update an uniform not continually.
here is the sample code:

Code:

osg::Uniform* lightPosU = 
          new osg::Uniform("LightPosition",osg::Vec3(0,0,1));
bumpMapState->addUniform(lightPosU);




Then I would like to update lightPosU, from Vec3(0,0,1) to Vec3(0,0,10);
As I know Uniform has a setUpdateCallback function which allows continually 
update one of concerned nodes once each frame, like this:

Code:

    class updateBumpShader : public osg::Uniform::Callback
    {
    public:
       virtual void operator() 
          ( osg::Uniform* uniform, osg::NodeVisitor* nv )
       {
          float angle = nv->getFrameStamp()->getReferenceTime();
          float x = sinf(angle)*.2f;
          float y = cosf(angle)*.2f;
          osg::Vec3 lightPos(x,y,.6f);
          uniform->set(lightPos);
       }
    };



then using following codes to setUpdateCallback

Code:

lightPosU->setUpdateCallback(new updateBumpShader() );




Is there a method to update the uniform only one time? just modify the value...
I have to customize the setUpdateCallback function?

Or Can I overwrite the uniform then re pass it to Shader?

Thank you!

Cheers,
Nan

------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=39282#39282





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