public final void setGamma(float gamma) {
        if(gamma<=0){
            throw new IllegalArgumentException("Gamma value can't be below or equal 0.");
        }
        if (material != null) {
            material.setFloat("InvGamma",1.0f/ gamma);
        }
        this.gamma = gamma;
    }
set to 0.0 to disable gamma correction

@param gamma the desired exponent (&gt;0, default=2.2)
jme3-effects/src/main/java/com/jme3/post/filters/GammaCorrectionFilter.java