20. Polygon Offset

• If backface culling and depth testing are turned on, sometimes triangles end up very close to the same depth.

• This creates z-fighting -- a problem where a part of the further polygon is displayed before rendering a closer triangle.

• For applying decals to surfaces, use

  
      glEnable( GL_POLYGON_OFFSET_LINE );
      glPolygonOffset( -1.0f, -1.0f );
  
  

• See glPolygonOffset() for details.