private Material loadMaterial(String textureFile,
			ColorRGBA diffuse, ColorRGBA ambient, ColorRGBA specular, 
			float shininess)
	{
		Material mat = new Material(assetManager, PHONG_SHADER);
		mat.setBoolean("UseMaterialColors", true);
    	mat.setTexture("DiffuseMap", 
    			assetManager.loadTexture("Textures/" + textureFile + ".jpg"));
    	mat.setName(textureFile);
    	if (diffuse != null)
        	mat.setColor("Diffuse", diffuse);
    	else // diffuse null is black
        	mat.setColor("Diffuse", Black);
    		
    	if (ambient != null)
    		mat.setColor("Ambient", ambient);
    	if (specular != null)
        	mat.setColor("Specular", specular);
    	if (shininess > 0)
    		mat.setFloat("Shininess", shininess);
    	return mat;
	}