OpenGL projects each face to the screen.  It then determines if the front side or the back side of the face is visible.

One can choose not to render back faces.  For example, when outside an opaque closed surface, the back faces are never visible as they are occluded by nearer front faces.  Therefore they can be culled, that is, not rendered.



Culling is enabled using
glEnable(GL_CULL_FACE);

And the side to cull is specified by glCullFace(GLenum mode), where mode is

• GL_FRONT
• GL_BACK (default)
• GL_FRONT_AND_BACK

Culling back faces may increase the rendering efficiency (framerate) and is enabled by default in the template.

High