(Solved) Bevel and shading

bitinn

Hi,

I don't fully grasp how bevel and shading works, even after learning many things about them.

I run into this problem quite often, when creating a fillet corner, this kind of shading transition shows up:




I would imagine this type of corner to have smooth shading transition, but it gives a slightly sharper transition on both side of the bevel. The effect is more noticeable at certain angles:




Q: Is it possible to do better? My main concern is metallic material reflection looks weird when applied.

(With normal)



(Without normal)

Axi5

Do you have a low poly wireframe to look at?

It seems as though you need extra support edges since your bevel is getting pulled out over the length of your model. Or maybe your bevel wasn't created with a depth of one.

bitinn

Axi5 said:

Do you have a low poly wireframe to look at?

It seems as though you need extra support edges since your bevel is getting pulled out over the length of your model. Or maybe your bevel wasn't created with a depth of one.

Sorry I didn't post it earlier, it suffers the same shading problem:

Axi5

I thought so, yeah you need to add some support edges to your bevel before you smooth. Otherwise the bevel will stretch along the length of the nearest edge.

It's easy to think that the bevel has enough geometry to keep it's shape but it's not always sufficient. Here's a quick example:



Left is without the support edges, right is with. And here's the low poly:



And FYI to other people yes I know that a lambert is not a good material to see the difference on, but the difference is still visible.

bitinn

Axi5 said:

I thought so, yeah you need to add some support edges to your bevel before you smooth. Otherwise the bevel will stretch along the length of the nearest edge.

It's easy to think that the bevel has enough geometry to keep it's shape but it's not always sufficient. Here's a quick example:



Left is without the support edges, right is with. And here's the low poly:



And FYI to other people yes I know that a lambert is not a good material to see the difference on, but the difference is still visible.

Thx for the explanation.

While searching for a definitive answer, I also run into this video from a few years ago: https://www.youtube.com/watch?v=zxE91h0SCCk

One follow up question:

- In my reply I was showing the low poly model. Not the base model for SubD. This is the base model for SubD (it suffers from the same problem for the reason you mentioned).




- My question being: Do I need to fix about this shading problem on the low poly? Can baking from a corrected SubD somehow relieve this problem? I know I should add the support edges, but wondering if baking is an acceptable fix or not.

Obscura

When you are face weighting the normals of such an object, there are multipla ways to smooth the rounded corners. Depending on the selection, the end normals can point differently. You can select those long side faces, and apply face normal. That should also fix your issue. If you don't do this, the normals will be still slightly bent out.

Axi5

bitinn said:

- My question being: Do I need to fix about this shading problem on the low poly? Can baking from a corrected SubD somehow relieve this problem? I know I should add the support edges, but wondering if baking is an acceptable fix or not.

If you're baking normals, then baking is an acceptable fix, the low poly does not need the support edges.

bitinn

Obscura said:

When you are face weighting the normals of such an object, there are multipla ways to smooth the rounded corners. Depending on the selection, the end normals can point differently. You can select those long side faces, and apply face normal. That should also fix your issue. If you don't do this, the normals will be still slightly bent out.

Thx Obscura. I know Chamfer and FWN are great for this. Just want to try out SubD baking for my own reasons (one good thing about hard edges: I can usually go chamfer without too much trouble, so it keeps all options open).

One thing though, I don't think my specific problem can be easily fixed with FWN? For example:

LaurentiuN

I think thats not really a problem when you have corners like that, i saw some real life objects that have that kind of shading.

bitinn

s1dK said:

I think thats not really a problem when you have corners like that, i saw some real life objects that have that kind of shading.

Yeah I could sort of leave it at that, but see the video I quote, really just a correctness thing.

bitinn

perna said:

That's how the shading would most likely be in real life, not a problem to be solved.

However, with some products, such as casings for expensive electronics, the producer goes the extra mile to avoid corner transitions, and you can do the same:

https://hackernoon.com/apples-icons-have-that-shape-for-a-very-good-reason-720d4e7c8a14

Nice, this reminds me that Maya 2018 actually added Superellipse as a primitive: 

(Though I am not sure if I can apply a superellipse bevel on cube...)

poopipe

To fix it with FWN you'd need a support loop for basically the same reason you need one in the subD. 

Obscura

I'm also wondering if you tried looking at them when they have some texture and a roughness map. Because I don't think the 99% of people would be able to point the "error" out then.

Prime8

perna said:

That's how the shading would most likely be in real life, not a problem to be solved.

However, with some products, such as casings for expensive electronics, the producer goes the extra mile to avoid corner transitions, and you can do the same:

https://hackernoon.com/apples-icons-have-that-shape-for-a-very-good-reason-720d4e7c8a14

Thanks for that, very interesting.

rexo12

perna said:

That's how the shading would most likely be in real life, not a problem to be solved.

However, with some products, such as casings for expensive electronics, the producer goes the extra mile to avoid corner transitions, and you can do the same:

https://hackernoon.com/apples-icons-have-that-shape-for-a-very-good-reason-720d4e7c8a14

That being said, CG is held to much more scrutiny than real life - you'll dismiss odd looking shading on an object IRL because 'that's just how it is', you know this is real life so there's no other way it can look. In CG however, your brain knows what it's looking at isn't real, and so it's a bit harsher on discrepancies - so sometimes realer-than-real is necessary. Just something to keep in mind.