black patterns on the sphere I'm new to both Blender and Sculptris. I was working on another model and it has similar problem. I first thought there was some problem with mapping the texture file but it seems like the import process went wrong.
I decided to see what it would do if I just export the default sphere into Blender from Sculptris.
Importing default sphere to Blender from Sculptris:
How the sphere looks in rendering:
Thanks a lot!

Edits:
I tried as suggested below to enter edit mode and hit ctrl+N. Something changed but it didn't solve the problem. Please see screenshots below.

Did I not get the ctrl+N right?

2nd edit:
Here's the file.
Sculptris seems to mess a bit with custom split normals data (or the export routines at least). When Custom Normals are present, some functions of Blender won't give you the expected result (and recalculating the normals is one of them, as well as setting an Edge Split ange). Delete this data to free the normals again. You can do this in the Mesh Data tab using the Clear Custom Split Normals Data button:

After this, all normals are pointing in the same direction again:
before

after

finally, recalculate the normals using Ctrl + N: