public void addTexture(Texture texture, String mapName, Texture masterTexture) {
        String sourceTextureName = textureName(masterTexture);
        if (sourceTextureName == null) {
            throw new IllegalStateException("Supplied master map texture has no asset key name!");
        } else {
            addTexture(texture, mapName, sourceTextureName);
        }
    }
Add a texture for a specific map name at the location of another existing texture on the master map.
@param texture A texture to add to the atlas.
@param mapName A freely chosen map name that can be later retrieved as a Texture.
@param masterTexture The master texture for determining the location, it has to exist in tha master map.
jme3-core/src/tools/java/jme3tools/optimize/TextureAtlas.java