public void setFaceCullMode(FaceCullMode cullMode) {
        applyCullMode = true;
        this.cullMode = cullMode;
        cachedHashCode = -1;
    }
Set the face culling mode.

<p>See the {@link FaceCullMode} enum on what each value does.
Face culling will project the triangle's points onto the screen
and determine if the triangle is in counter-clockwise order or
clockwise order. If a triangle is in counter-clockwise order, then
it is considered a front-facing triangle, otherwise, it is considered
a back-facing triangle.

@param cullMode the face culling mode.
jme3-core/src/main/java/com/jme3/material/RenderState.java