It’s also happening on my other machine, which has a totally different card. So not sure that’s the issue…
NVIDIA Corporation
GeForce GT 650M/PCIe/SSE2
OpenGL version: 4.2.0
Render version: 4.2
Shading Language: 4.20 NVIDIA via Cg compiler
Driver Date: 8-30-2012
Driver Version: 9.18.13.623
Maximum Texture size: 16384 x 16384
Z-Buffer depth: 24bits
Maximum Viewport size: 16384 x 16384
Total Video Memory: 1 GB
Only transparent material display from grasshopper seems to be affected. Using custom preview w/ an opaque material registers no artifacts.