private Geometry buildCube(ColorRGBA color) {
        Geometry cube = new Geometry("Box", new Box(0.5f, 0.5f, 0.5f));
        Material mat = new Material(assetManager, "TestMRT/MatDefs/ExtractRGB.j3md");
        mat.setColor("Albedo", color);
        cube.setMaterial(mat);
        return cube;
    }
Create a cube with the specified color,
using a custom unshaded material that outputs 4 textures:<ul>
<li>red channel only to location 0,</li>
<li>green channel only to location 1,</li>
<li>blue channel only to location 2,</li>
<li>merged RGB to location 3.</li></ul>

@param color the desired albedo color (alias created)
@return a new Geometry with no parent
jme3-examples/src/main/java/jme3test/post/TestMultiRenderTarget.java