[CURRENT ISSUE 64-bit] Sculpture blocks not properly rendered

When my sim is sculpting, the blocks of material are solid black blocks, with no color or texture, that also cover sims or objects in front of them:

This applies to clay, wood, metal, stone, and topiary blocks, each of which has its own patterns.  The only exception is ice, which while still a solid block, does change from day to evening to night:

Previously, ice blocks would have a slight tint to reflect world lighting but would still look like, well, ice.

The sculptures themselves look perfectly normal, both when finished and when sticking out of the block of material from which they're being created.