protected MatParam findMatParam(String varName) {
        for (MatParam matParam : materialDef.getMaterialParams()) {
            if (varName.equals(matParam.getName())) {
                return matParam;
            }
        }
        return null;
    }
Finds a {@link MatParam} in the {@link MaterialDef} from the given name.

@param varName the material param name.
@return the found {@link MatParam} or null.
jme3-core/src/plugins/java/com/jme3/material/plugins/ShaderNodeLoaderDelegate.java