How to use polygonOffset solving Z-fighting poblems

I see that THREE.scene.overrideMaterial defines the polygonOffset parameters and THREE.WebGLRenderer calls glPolygonOffset(). but there are some errors when running
console.error( _gl.getShaderInfoLog( shader ) );

I use FireFox 16.0 and My code likes this:

            var material1 = new THREE.Material();
        material1.polygonOffset = true;
        material1.depthTest = true;
        material1.polygonOffsetFactor = 1;
        material1.polygonOffsetUnits = 0.1;
        _scene.overrideMaterial= material1;

How to use polygonOffset correctly.

Thanks,

http://en.wikipedia.org/wiki/Z-fighting

[makc]

@spite like this?

[WestLangley]

@kylebakerio See https://stackoverflow.com/questions/31539130/display-wireframe-and-solid-color/31541369#31541369.