@Override
    protected void declareAttribute(StringBuilder source, ShaderNodeVariable var) {
        declareVariable(source, var, false, "in");
    }
{@inheritDoc} in glsl 1.5 attributes are prefixed with the "in" keyword
and not the "attribute" keyword
jme3-core/src/main/java/com/jme3/shader/Glsl150ShaderGenerator.java