[Bug] Models darken at some viewing angles

Summary:

Some models suddenly turn flat black after small changes in viewing angle. They return to normal appearance after viewpoint is returned to original position.

For an example, see the head of the horse on the right side of these images:

The head (excluding lower jaw), in this image, is a separate .qb file from the other components of the body.

Steps to reproduce:

I’m afraid I don’t have much insight here. The one thing that occurs to me is that this might be some kind of, um, occlusion artifact (not sure about the word here). Notice that in the second picture, a tree shadow also disappears; both disappearances may be due to the game believing that area of the screen can’t be seen because a tree is “in the way”.

Notes:

The horses are my own models. In this image they’re acting as static objects, like trees.

Versions and Mods:

I’m running Stonehearth 0.1.0 (r42). The only mod on this particular install is my own mod that adds the horses (they’re standing in as trees).

System Information:

OS: Windows 7 Professional 64-bit
CPU: Intel Core i7-3720QM CPU @ 2.60GHz
Memory: 8 GB
Graphics Card: GeForce GT 650M
Trivia: This computer is physically a MacBook Pro, but I’m dual-booting Windows on it because games.