Remember the problem that I tried before in ZBrush that failed to bake the normal map directly with the high face number model? I searched for relevant information on the Internet, and they all used the UV master in ZBrush to simply unfold the UV and then bake it directly. So the question is, the textures I exported with the high-surface number model and the textures baked in the Substance Painter of the low-surface number model out of the topology have different UVs. How can they be linked together?
Because I didn’t understand the process, I decided to bake the high face number model directly in SP instead of ZBrush.
And when I talked to Karl about this issue, he asked me to open discord, and he would show me how to bake the same normal map as the low polygon model with ZBrush.
First of all, we first sculpt a model, this model is only dynamesh, it is like a mid-surface model. Karl used a dog and carved it, adding details to it.
Then he copied a dog model and used ZRemesher on it to make the edges clearer and reduce the number of faces. Now his subdivision level is 1.
Next, Karl now selects the mapping model when the subdivision level is 1. Mapping can map the details of the model with high polygons to the model with low polygons, but it must be ensured that both models are visible in ZBrush. Then he increased the subdivision level to 2 and continued mapping. Finally, he increased to 4, and after each subdivision, he will perform a mapping. In this way, every subdivision level of the model after ZRemesher has details. Even we can directly increase the subdivision level and continue to sculpt to make a model with a higher number of faces.
The subdivision level 1 of the copied model is the low-poly model that has been topologicalized. Karl exported it and put it into RizomUV to expand the UV. Then import the low polygon model with UV information into ZBrush, so that we can keep the high polygon model and the low polygon model in the same shape, and also have UV information.
Then he opened the multiple texture exporter and selected the textures he needed. It’s worth noting that the subdivision level under the normal map menu represents the subdivision level from which to start baking. Karl recommends starting from level 3, and then ZBrush will automatically bake from level 3 upwards. The details of the hierarchical model are baked out.
The normal map baked in this way is perfect. But if there are black edges, check if the model
shape difference between before and after copying is too big (so you can subdivide after mapping and then sculpt), otherwise you have to go to Photoshop to adjust.
I am very grateful to Karl for sharing this little trick with me, but it doesn’t work just to listen to it without practicing, so I decided to try it myself.
First I opened the dog model in ZBrush, clicked dynamesh to increase the number of faces, and then I sculpted two random strokes and copied the model.
After I used ZRemesher on the new model, I clicked on the low polygon model, and then selected the mapping after making the two models visible. In this way, there is a detail in the case of subdivision level 1, and then I projected it in the case of subdivision level 234.
Then I also tried to lower the face number to 5, and then sculpt, so that the low face number model will also be changed in shape. This is the situation of the low poly model after I engraved the high poly model. Finally, I unfolded the UV from RizomUV and imported the model. If I use a different model, ZBrush will prompt us that the topology has been changed.
Finally, I successfully exported the normal map!