Can anyone explain the difference between the three depth testing
options available on renderers such as Sphere and Cube? (None, Read/
Write, Read-only)
Quartz Composer simply exposes the OpenGL depth buffer settings (you
will need to google to find more info on that). Put simply, a depth
buffer is a "depth representation" of the 3D scene and is used to
compute visibility and intersection of 3D objects in the scene.
There are three possible ways to use a depth buffer when it comes to
rendering an object in the scene:
* None: depth testing is disabled - the object is simply drawn on top
of everything
* Read-Only: depth testing is enabled - the object, when drawn, is
tested against the depth buffer, and parts of it that are invisible,
because behind objects previously drawn with depth buffer in read /
write mode, are discarded.
* Read / Write: same as above, except the contents of the depth
buffer is updated to take into account the visible parts of the object
