protected void declareVariable(StringBuilder source, ShaderNodeVariable var, boolean appendNameSpace, String modifier) {
        declareVariable(source, var, null, appendNameSpace, modifier);
    }
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 + "_"
@param modifier the modifier of the variable (attribute, varying, in , out,...)
jme3-core/src/main/java/com/jme3/shader/Glsl100ShaderGenerator.java