What would be the easiest way to make a bump map of the dimples on a citrus fruit such as an orange or lemon in gimp/photoshop without using pictures of it? e.g:
The skin is fairly smooth with some big dimples. A first approximation would be (in the GIMP):
I suspect you'll find that that gives too much clumping, so the second approximation would be to replace step 2 with random nudging from a hex grid. Either do this in code or create a hex grid in the GIMP and use Filters | Noise | Spread.
Create a flat plane of orange skin in high definition 3D (ie. a Lot of polygons + an orange colour texture).
Use it :-)
This link Might help you get the general idea of baking.