ygSunshine's picture

Quads draws as tessellated triangles with wireframe?

Hi all,

I am trying some simple OpenGL rendering using OpenTK. When I draw a rectangle:

GL.Color3(0.85, 0.85, 0.95);
GL.Vertex3(-bgSize, -bgSize, -bgSize);
GL.Vertex3(bgSize, -bgSize, -bgSize);
GL.Color3(0.1, 0.1, 0.9);
GL.Vertex3(bgSize, bgSize, -bgSize);
GL.Vertex3(-bgSize, bgSize, -bgSize);

It renders with the borders of the two tessellated triangles. That means, it renders the polygon + the tessellated wireframe! This looks like a nice free gift to have, but what I want is just a plan polygon..

Did I miss out something? What are the things I should check?

Thanks in advance.

Inline Images
Quads with tessellated triangle wireframes


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the Fiddler's picture

This doesn't look quite right. Check your initialization code:

  • Are you changing the polygon mode (GL.PolygonMode) to something other than fill?
  • Are you using front-face culling?
ygSunshine's picture


I tried to use/not use things like
GL.PolygonMode(MaterialFace.FrontAndBack, PolygonMode.Fill);
But always the same.

The problem occurs on my Vista machine with NVIDIA Quadro FX1700, but same code works fine on my XP laptop with ATi Mobility FireGL V5250. So I guess it is somehow related with the graphics card/driver..

Any one has any idea?