Hi Egon, your code work wonders, thanks so much.
I am exploring one more feature, that is to set transparency on the 'cutted away' section. My approach is to alter the alpha value in the vertexShader.src by using setUniform("shader", 5f), but it doesn't seem to set any opaque-ness at all. My reason for doing this instead of simply using setTransparency is because I wanna show the full 3D model, ie the 'remaining-cutted' section be shown will full solid renders while the 'cutted-away' section be shown with some opaqueness. This way I think its possible for me to setShaders twice (i'm not sure if its possible yet), one shader to define the solid shading for remaining cutted section, while the second shader to define the opaque shading for the cut away section.
Any suggestion?