Remeshing a character should NOT remove the Opacity map
In the pictures below, you can see that the most obvious difference between the original character and the remeshed character is the hair. It looks very different. That is because the remeshed character has no Opacity map for the hair.
When you do the remesh, the Opacity map needs to be carried forward. It can use the same re-mapping algorithm as the Diffuse (Base Color) and Normal maps. Anything without Opacity data should default to "Opaque" and be filled in as white (visible) in the opacity map. If there are no Opacity maps at all, then it is okay to leave that channel empty.
The Opacity map should apply at least to LOD 0 (the starting point), LOD 1 and LOD 2. At least that far. Sometimes people use Opacity to hide large areas, short sleeves versus long sleeves, or even to simulate amputated hands, and those situations would be extremely obvious in LOD 1 and LOD 2. If there are performance concerns for the lower levels, perhaps for LOD 3-5 it could be an option to retain or discard the Opacity channel.
This should apply to all items being remeshed: body, hair, clothing, accessories, whatever.
<<< Pictures >>> 1 - Original 2 - Remeshed... not only do the hair strands now look completely different, but notice the dark band across the top of the forehead 3 - LOD_0 and LOD_1 side-by-side... the change to the hair makes it look like two different women 4 - Showing the Opacity channel is completely missing, but other channels got remapped
We removed the opacity map, because once remeshed the meshes inside were deleted, if we keep the opacity map, it will be see through inside.
Hey! I attached a jpeg file in my previous comment. Where did it go?
Oh well... you can SEE THE PICTURE in this forum post: https://forum.reallusion.com/FindPost381223.aspx
I'm gonig to attempt the file attachment again, just for experimental purposes.
I even waited for the uploading process to finish before submitting the comment....
Ah ha! The "progess bar" indicated it was done uploading, but apparently wasn't "really" done.
This time I waited much longer and the thumbnail finally appeared. It took a long time for the half-size image to finish, and a long, long time for the full-size image to finish.
Opacity demonstration - half size.jpg
I made a new picture, showing the same character before-and-after remeshing.
The original skirt and top got shortened through the use of an Opacity map.
As you can see, the remeshed character needs to get really, really, really small before the loss of opacity is no longer noticeable.
I suggest that even an imperfect opacity map would be far superior to the total absence of the opacity map.
SEE ATTACHED PICTURE...
Thank you Gerry (wires) for the additional tests and examples in the forum post. Excellent work.
Those new pictures clearly demonstrate this issue is as serious as I thought and my concern was justified.
And thank you for the original images you posted (the ones I used when reporting this issue) that originally brought this issue to my attention.