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