Drawing concave polygons

OpenGL OpenGL: Basic Coding
1

Hi

I’m looking for example of drawing concave polygons (in FILL mode).

Of course one of the solutions is to divide the original polygon in triangles, but is there any OpenGL alternative?

I heard it can be done with the stencil buffer. Is there any sample code?

Thanks in andvance

2

OpenGL redbook describes very well about drawing concave polygon using stencil buffer.

Here is my example using stencil buffer, drawing 3 non-convex polygons;

  1. simple concave quad.
  2. a polygon with a hole in it.
  3. self intersected polygon.
    It works #1 and #2 cases except #3.
    stencilTess.zip

Also, check out OpenGL Tessellator , too.

3

Thanks a lot
(How simply it was! :slight_smile: )