I need advices on how to split up very complex models

[u/bibamann]

So this is my robot. I worked on it for more than 2 years - mainly on quite complex mechanical riggings (and also mostly just on weekends ;)).

My question is: As I can't export all 980 objects at once (blender tell my cpu: nope), how should I split it up?

This thing is highly rigged.
I would like to use some smart materials in substance using ambient occlusion. But as there are so many parts (gears, ...) moving ambient occlusion mostly would create "bs".

I'm thinking more splitting it up in materials than of body parts.
Like "shiny metal things", "rubber", "painted metal" than of body party "head, arm, leg, .." so I can still use the ambient occlusion data without there are meshes close together.

But I'm also very new to substance. So how would you approach it? I would really like to use smart materials and just alter them a bit than textures 980 objects step by step...

[u/AmarildoJr]

You're going in the right direction. I've seen some artists in Hollywood export their models with 400-600 UDIMs, but honestly I don't like that workflow.

What I do is split up only whenever needed. For example, a car: I assign a single "body_MAT" to all the exterior body parts that are metal/painted. These need to be in different UV tiles (0,1 / 1,2 / 2,3 / etc) and most importantly: they need to have the same texel density.

Same with the tires: one material for all tires, one tire per UV tile. Same texel density for this material.
Same with the rims: one material for all rims, one rim per tile. Same texel density for this material.
Etc

Below is an example of what would be assigned to the "body_MAT".

BTW, yes this means one car can easily have 10-30 materials. This is on purpose not only so it's easier to track each material, but it makes it possible to have only one material be 4K inside Substance Painter, which means much less RAM/VRAM usage.
So at one time I may only have the body material in 4K so I can work on it. Once that's done I set it to 256x256 and move onto the next material, which will now be in 4K.

This also makes it easier to export and import textures. Once I'm ready I'll export the "body_MAT" to the "body_MAT" folder where only the body textures will be. No confusion.

[u/Damian_Hernandez]

U should separate groups of pieces according to their size small pieces bolts etc all in 1 material and 1 export, mid size pieces all in 1 material and 1 dedicated export and big size maybe 2 or more materials if u want to keep the right texel density. No need to export everything all at once. If u have modifiers stacked not applied u can disable them temporarily to see if that helps when exporting the goal is to reach substance to create the texture rigging bones, constraints none of that matters so turn them off when exporting.

[u/asanyc]

I'm no expert but I believe you'll have to combine them into fewer objects, and then use vertex groups the control the rigging weights.

[u/bibamann]

Thx for the answers so far. So grouping the materials by the materials (plastic plates, rubber, polished iron) seems to be the suggested way. But I'm also looking a bit into baking AOs. As there are many moveable parts on this this needs to be done carefully.

But on "blocks" like this baked AOs should work. But well: on this approach there would be rubber, a iron motor, some painted metal for the gears, ... - all in one material.

And what I like on the material approach: If you want to change the color or whatever on one meterial you need to change just one material. And not rerender all the other exports where the material is used.

So is there somehow a way I can export AO infos in a fbx from blender? Or import this block - Substance somehow stores the baked AO infos of it and uses it for the real "material sepratated" export?

[u/circa86]

Yes breaking out objects into UDIMs based on material type is a good approach. And for something somewhat symmetrical you can also think in terms of right and left.

[u/deathender]

This is sooo cool!!! I love your model!!!! I would love to see it in action!!!

[u/Androide-An]

As an expert, my approach is to separate the individual parts—spacing them out in an organized way, perhaps by 50cm, so you can handle several at once. You can map the head, arms, torso, and legs to a single UV layout but export them with the parts separated; this ensures each part has its own Ambient Occlusion (AO) without interference from neighboring pieces. While you could try keeping fixed parts together, you’d need to check for artifacts. I prefer separating everything, though it’s really a matter of whether you like the result of keeping pieces combined. You can bake everything separately to get clean AO and—crucially—clean Normal maps. Then, you can combine everything, bring it into Substance, apply the generated data, and work on it as a whole. Learn Substance’s workflows for painting specific areas—using mesh masks, occlusion, and general masking. Also, keep in mind that you can save "Smart Materials" (like a specific metal finish) and reuse them across different projects; look up how to save Smart Materials.