I want to draw a quad (not two triangles). I actually know that triangles are faster, as I answered this question.
But let's say I am building a 3D modeling tool. It makes sense to draw a quad for the user (like Maya and 3D Max do) and not two triangles especially if he is actually working with quads. Is there any other option than using geometry shaders to accomplish this?
I understand that I can draw two triangles and make them co-planer. Unfortunately this will still make the two diagonal points connected, I don't want this. I want a pure quad. I don't want the line connecting the two points, Exactly like what you see in a modeling tool. I am actually rewriting a modeling tool that I wrote few years ago, and can't get the same behavior I got with the older OpenGL.
Here is an image of the tool I am re-writing using modern OpenGL. I used QUADS, so the question is about an alternative that gives this same behaviour especially I am using two pass rendering to render the model and it's outline. That's why I don't want the line separating the two triangles to appear.