@Override
    protected void declareVarying(StringBuilder source, ShaderNodeVariable var, boolean input) {
        declareVariable(source, var, true, input ? "in" : "out");
    }
{@inheritDoc} in glsl 1.5 varying are prefixed with the "in" or "out"
keyword and not the "varying" keyword.

"in" is used for Fragment shader (maybe Geometry shader later) "out" is
used for Vertex shader (maybe Geometry shader later)
jme3-core/src/main/java/com/jme3/shader/Glsl150ShaderGenerator.java