Knight model becomes invisible on coming close

[jdrueckert]

During the testing of Terasology/LightAndShadowResources#62 it became apparent, that we have some seemingly graphics-dependent issues with the knight model. After spawning the knights with spawnPrefab redKnight and spawnPrefab blackKnight respectively, approaching them within about 3 blocks will in some cases make them become invisible, in others not.

I, running a Radeon HD 7800 series graphics card, can come very close to the model without it becoming invisible:

@skaldarnar and @4Denthusiast on the other hand, both running nvidia graphics, cannot:

The interesting part is, that this only seems to be the case with the knight model, other models such as the bishop are fine and can be approached and stay visible with either graphics.

[jdrueckert]

Could be related to MovingBlocks/Terasology#4180