@Override
    protected void initFilter(AssetManager manager,
            RenderManager renderManager, ViewPort vp, int w, int h) {
        material = new Material(manager, "Common/MatDefs/Post/GammaCorrection.j3md");
        material.setFloat("InvGamma", 1.0f/gamma);        
    }
@author Phate666
@version 1.0 initial version
@deprecated use the Gamma Correction setting instead.
jme3-effects/src/main/java/com/jme3/post/filters/GammaCorrectionFilter.java