Apologies if this is in the wrong forum as perhaps it's a general problem, but I am specifically using the DirectX 11 runtime. I'm sure my problem is some basic matter that I just don't understand yet and I'm hopeful someone can help. I'm new to graphics, and sometimes I don't know what it is that I don't yet know.
Here's my situation. I have a dirt-simple DX11 renderer into which I'm loading mesh data that was parsed in from FBX (created in Maya and Blender). As long as the mesh is a simple primitive like a cube or a sphere everything works wonderfully. The mesh is recreated faithfully on my screen, and in fact I was getting to work on pixel shaders when I noticed something odd.
If the mesh is less simple -- say, if I grabbed a face in Maya and moved or extruded it a bit -- then that extruded geometry does not clip properly when I render the mesh. Exhibit A:
As you can see, the modified geometry doesn't cull correctly.
I didn't know what to make of that so I made a couple of geometry shaders to help me debug. That's what you see in the video. The lines are the calculated face normals and the vertex colors are coded R, G, B in the order received by the geometry shader. I had originally thought that the offending polys might be getting wound cw rather than ccw as a result of operations in Maya, but they all appear to be ccw. The calculated normals also appear to be pointing the right way.
I've looked at my depth/stencil states and they appear fine, but I expected that since I can draw spheres and cubes and such correctly all day. My near clip plane isn't set to zero; I thought of that.
Frankly I don't know what else to check. This has been driving me batty all day. Please send help.
** edit
Just wanted to add that I do have the debug layers going and I'm checking my HRESULTS and nothing is amiss as far as that goes. And I'm drawing with an opaque blend state.