public RenderState getPreShadowForcedRenderState() {
        return forcedRenderState;
    }
Returns the pre shadows pass render state.
use it to adjust the RenderState parameters of the pre shadow pass.
Note that this will be overridden if the preShadow technique in the material has a ForcedRenderState
@return the pre shadow render state.
jme3-vr/src/main/java/com/jme3/shadow/AbstractShadowRendererVR.java