protected void declareVariable(StringBuilder source, ShaderNodeVariable var, boolean appendNameSpace) {
        declareVariable(source, var, appendNameSpace, null);
    }
declares a variable, embed in a conditional block if needed
@param source the StringBuilder to use
@param var the variable to declare
@param appendNameSpace true to append the nameSpace + "_"
jme3-core/src/main/java/com/jme3/shader/Glsl100ShaderGenerator.java