CW or CCW triangles ignored by the render engine

[ArchlineXP]

Is there any way to ignore the CW or CCW triangles during rendering? Some objects are rendered incorrectly, miscolored triangles appear on the surface instead of the color I set. I attached a photo of it.

[johguenther]

No, there is no backface-culling in OSPRay. The artifacts on the chairs indeed look like z-fighting: are there multiple surfaces overlapping at the same spot (two chairs put in each other)? Maybe also the vertex-normals are too extreme (parallel to the surface). Which material is used? Do the artifacts also appear with the SciVis renderer / OBJ material?