I just found out what I was missing with HD geometry. I’m currently working on a production and we are using HD sculpting for the first time.
My question is essentially a math one. For polypaint. are colors assigned to the final map by vertex or by polygon? And depending on the answer, how many polys would you need to make the maximum 8192 map?
And are the maps for displacement and normal maps also based on vertex or polygon?
Polypaint is essentially vertex coloring. A map of 8K has approximately 64 million pixels. How many of those are available for actual mapping will depend on the UVs. With automatic mapping such as PUV tiles you might get 90% but with pelt-type mapping (such as from UV Master) considerably less - something like 50%. For pelt-type mapping then you will lose some polypaint if you divide over 32 million. However there may still be advantages to doing this as ZBrush does a good job of resampling. Also, if your mesh topology is uneven then the higher HD polycount will avoid loss of definition in the areas with fewer low-res polys.
Normal & displacement creation is based on the vertex positions, so the same considerations apply.