Thursday, January 2, 2025

Strand-Based Hair and Hair Guides

In DAZ Studio we can give characters Strand-Based Hair (SBH), which corresponds to hair curves in Blender. Unfortunately, SBH often has a very high vertex count, which makes it rather unusable unless you have lots of patience. However, the DAZ Importer has an option to import hair guides in addition to the SBH itself, and the guides are much more lightweight and therefore better suited for Blender hair.

Here is Aiko equipped with a new hairdo made from SBH.
We can inspect the vertex counts with the mesh statistics tool. Aiko herself has some 16,500 verts, but the hair has a whopping 2,5 million verts, which will make it very heavy to animate.
Exporting a dbz file to Blender takes almost 70 seconds, compared to between 5 and 10 seconds for a typical transmapped hair. Waiting for the export script to conclude is quite painful, but there is nothing to do about this.
In Blender, turn on the "Import All Hair Versions" option. This will import the hair guides in addition to the hair itself.
Two polyline hair meshes are imported into Blender: the main hair with 2,5 million verts, and the hair guides with 200,000 verts. A difference of a factor around 12.
Now we delete the main hair and convert the hair guides to hair curves. 200,000 verts is still somewhat high for my taste, but the result with ten render children is quite good, so there would be nothing to gain by keeping the full hair mesh.