I'm trying to put together a quick demo using iOS GLKit to render a retail store map using OpenGL using the source CAD files. I was able to render the walls and aisles in 2D, then programmatically add some artificial depth to create a series of cubes. All of this looks fine when looking top down, but I noticed that when I turned on the floor (with a z-value that is well below the aisles and walls that some of those objects are actually rendered under the floor:
...however if you rotate the model you can see that nothing is actually below the floor and some of the aisles are rendering outside of the wall:
You can view the code at StoreMapGLKitViewController.m, it all seems pretty simple to me, but I'm sure I'm making some kind of OpenGL rookie mistake.
Ends up that the depth buffer wasn't setup correcting so the depth test wasn't doing anything. Adding the code below fixed it.
GLKView *view = (GLKView *)self.view; view.drawableDepthFormat = GLKViewDrawableDepthFormat24;