Add a System.out.println(depthTexture)
inside setDepthTexture
method just like I did and we will see if it is null or not:
fogFilter = new FogFilter() {
@Override
protected void setDepthTexture(Texture depthTexture) {
super.setDepthTexture(depthTexture);
System.out.println("depthTexture=" + depthTexture);
}
};