Difference between subdivision surface and multiresolution?

Hey there! What is the difference between subdivision and multiresolution modifier?

Why do game devs only use multiresolution for baking high Polly to low Polly?

Can it be done using subdivision surface? If so what’s the pors and cons

Sometimes I make a model, give it supporting loops and apply multiresolution, it breaks like hell! But then I apply subdivision on the same model and it works as intended why?

Multiresolution is intended to be used with further modification of generated geometry, i.e. sculpting - you can add finer details on higher subdivision levels. Subdivision surface is not intended to be used like that.

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Multiresolution is a more advanced type of subsurf meant for sculpting. What it does is you take your basemesh, add subsurf, add a lot of subdivisions for sculpting and sculpt. Then you can turn down the subdivisions for render and viewport while retaining most of the quality. That’s where the “multi” in the name comes from.

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Any difference between a highpoly and lowpoly model could be baked. But that doesnt mean that it makes sense. I’ll get back to this in a minute.

The term Multires generally means that you can model on multiple mesh resolutions and propagate them (normally to higher (finer) levels). Depending on the multires algorithms used propagation to lower levels is also included or not. As Stan_Pancakes said, its eg useful for modifications on a geometry that itself should stay as is, eg for pipeline reasons.

Subdivision is different, its calculating a smoother version from a rougher basegeometry by subdividing faces and “smoothing” them. Simply spoken its just an algorithm. The input is the basemesh and one single integer that defines the amount of subdivision steps. So you just edit the basemesh itself. And thats why reprojecting the detail doesnt really make sense. The information is already stored implicitly in the lowpoly mesh as its resulting in a defined smoother version based on the subdiv algorithm. There is not really custom shape information stored in higher levels. That is the difference to multires. And so for subdivision it’s possible to simply take the lowpoly mesh and let it subdivide on a gpu at runtime in a game instead of baking it to displacment maps.

Thats blender multires specific, the codebase needs some more work to rule out bugs. Subdiv is much more stable.

Thanks a ton mate! That really cleared a lot of things and hope blender Dev’s fix multi res! But since I predominantly work with Hardsrface models I can use subdivision instead of multiresolution?

Also I’m new to game asset modelling hence when can I add bevels at the the low Polly model stage?

Or add no bevel at all since subdiv makes the edges smooth and rounded?

Or at a later stage when making the high Polly? Only problem when I make the high Polly is the supporting loops don’t let me bevel!

And is it good to bake bevels? Sorry for the questions i just want to be clear!

Thanks a ton!

Thanks mate!

Sure can you use subdiv surfaces for that. If you are new to all this, have a look at edge creases and how they work for subdivision surfaces and in blender first, thats a must for modeling hard edges on subdivion surfaces. And taking a look at some youtube blender videos for hardsurface modeling should get you more informed on typical workflows in blender.

Bevels for example can be modelled directly, added as a byproduct of subdivision surfaces, shaders, bevel modifiers.
Supporting edges or edge creases on the basemesh are alternative ways to control the smoothing amount of edges for subdivision surfaces.
For the bevel modifier you can define vertex groups to restrict the amount of edges included.

And for all these bevel methods its rather about what is benefitial in a specific situation than always stick to one of these methods.
Blender can work with ngons, make use of that and have an eye on a good topology.

There are so many “depends on” cases, that its hard to answer your questions in short.

Btw. for hardsurface modeling there are some quite nifty addons on available like this one.

Have a look at it. I hope that helps. Good luck!