Zbrush sculpted C4D model poly reduction and texture baking

[Delphis]

Hello,
I purchased this model (C4D+ZBrush format):
https://www.cgtrader.com/3d-models/animals/reptile/chameleon-quaricornis-four-horned-chameleon
The model is ZBrush sculpted and it's heavy to work with (7Mil polygons).
Material is vertex color driven but it has a .BMP color map as well.

I would like to reduce its poly count and bake Color and Displacement texture for use with lower-res model for rendering with Redshift/C4D.

Do you have some suggestions or tutorials for the efficient poly reduction and texture baking process?
Thank you.

[Dr. Sassi]

Hi Delphis,

If you like to animate to a certain degree, perhaps the Mesh Deformer is the way to go, as that can be very rough and allows you to run even heavy models.

Let us start with the color first.

The ZRemesher in ZBrush is a tool that reduces the number of polygons.
Available in Cinema 4D as well.

Without any idea of your model (Thanks for the link, but that is just a few pictures and some data), I can't say anything about UVs; without UVs, baking textures is impossible.

Remember that 70M (or per link 18M) polygons may provide a smooth edge (all in limits) to small PolyGroups "UV Islands". However, the new low-res mesh can't reproduce those smooth edges, naturally not. Seams will most likely have problems.

Even the Un-Subdivide function in Cinema 4D has no option to generate the low-res UV data needed for your request.

Some might suggest storing the textures temporarily in the Vertices; I'm not a fan of that for various reasons. Color Space problems and the lack of a way to define reduction or conversion are other reasons.

In Cinema 4D, there is an option called Property Transfer, which has a UV Transfer function. How well it can provide its power depends on the model and the amount of reduction. If that works, the original textures can be used. With that, baking is the next step, but if UVs overlap, the baking process will overwrite those areas with the latest data it has to write, resulting in unwanted changes. This is also something I can tell from the information I have so far.

I'm sorry to be that blurry. It's not my pleasure to do that to you, and certainly not fun for you.

All the best

[Delphis]

@Dr-Sassi said in Zbrush sculpted C4D model poly reduction and texture baking:

If you like to animate to a certain degree, perhaps the Mesh Deformer is the way to go, as that can be very rough and allows you to run even heavy models.

Yes, that's what I'm doing, using the bend deformed to bend the head, but it's very slow.
Whenever I select the mesh or it's tags, C4D halts and takes 1min to be responsive again.

Without any idea of your model (Thanks for the link, but that is just a few pictures and some data), I can't say anything about UVs; without UVs, baking textures is impossible.

Here is the UV map screengrab:
https://ibb.co/NmbhxsY

Here is the mesh topology look:

Here is a look with the vertex map:

The provided image texture map is pretty bad:

Remember that 70M (or per link 18M) polygons may provide a smooth edge (all in limits) to small PolyGroups "UV Islands". However, the new low-res mesh can't reproduce those smooth edges, naturally not. Seams will most likely have problems.

Yes, that's why I wanted to bake a displacement map, I'm sure I saw long-time ago tutorial on how to bake a displacement map from hires model do lowres model with C4D sculpting tools, but can't find it again.
I'm sure for displacement that its possible but not sure how the vertex color map would transfer.
Thank you.

[Dr. Sassi]

Hi Delphis,

Thanks for the data.

Thank you for the UV information. This is good and bad news:
It is bad, as that is not anything useable for this model, but the good news is that it is easy to reproduce, as it is all based on orthogonal "views". Why bad? Because a six-sided view does not represent an organic object well.

There is an option to create a low-res version of a texture from a hires Vertex map. Is it working 100%? It depends on the preparation.

The idea is for the new low-res mesh (Remesher, for example) to be just the tiniest amount smaller than the high-res model.
The Vertex information goes into the Luma channel (Standard Render, Material).
After preparing a good UV map, the low-res, which can be just done with many of the options, e.g., Packed, needs a "Chrome" material.
This allows one to bake the information from a "larger" object. The process is demonstrated here in 60 seconds to give an idea (not a tutorial) about it.
https://stcineversityprod02.blob.core.windows.net/$web/Cineversity_Forum_Support/2024_Clips_DRS/20240620_Res_Bake_Tex.mp4

I hesitate to share those things without more specific information, as general questions in 3D most likely do not give workable answers. At least, this is my experience supporting and mentoring artists around the globe for two decades.
I say that because that is a proven way, and it is not to be just complicated.

The Baking of the Displacement is described here:
https://help.maxon.net/c4d/en-us/?_gl=1ojv8bf_gcl_au*MTQ5NzQ3MDQ5MS4xNzEyMzQzNjY2#html/49938.html?Highlight=texture%20baking

All the best

[Delphis]

C4D Remesh worked just fine, it respects vertex color data so I was able to make low-res model from 7M to 600k polygons (with a pretty good new vertex color map) to work/test renders , and I just switched ON the hi-res model layer for final rendering.
I could use Xref object to have a lower file size working scenes (hi-res model=600MB), but I had no time to test it, I will try how that works.

[Dr. Sassi]

Thank you very much for the reply, Delphis.

It looks like you are up to a great project; my best wishes for this!

Enjoy your weekend.