No, HOpenGL doesn't do anything behind the scenes; it's not that OpenGL can't render convex polygons so much as it's a bad idea to count on it rendering them. It's entirely implementation (read video card) dependent as to whether it can render them and if it can how complicated they can be before the implementation breaks. It's sort of like how IE and Firefox will render HTML that isn't XHTML compliant or even truly really HTML. It's much better practice to tesselate using the GLU functions or your own tesselator than it is to count on features that are only there to correct the occasional programmer mistake. On Sun, Mar 22, 2009 at 5:27 PM, Rafael Cunha de Almeida wrote:

I'm reading the red book and it says opengl cannot render convex polygons. Yet, when I compile this code:    renderPrimitive Polygon $ do        vertex $ Vertex2 0 (0::GLfloat)        vertex $ Vertex2 0 (3::GLfloat)        vertex $ Vertex2 4 (3::GLfloat)        vertex $ Vertex2 3 (1.5::GLfloat)        vertex $ Vertex2 4 (0::GLfloat) The convex polygon is displayed correctly. Does hopengl do something behind the scenes or I just "lucked" out that my opengl/hardware can handle this particular convex polygon case? _______________________________________________ HOpenGL mailing list HOpenGL@haskell.org http://www.haskell.org/mailman/listinfo/hopengl