UV seams in Arnlod

DC74

Hello! 

I am new in 3D, so I have a noob question about UVs, seams, and the following render in Arnold. Currently I am checking the following pipeline: 

1. High poly in Maya.
2. Low poly in Maya. 
3. UVs for the low poly in Maya. 
4. Baking in Substance painter.
5. Exporting the textures back to Maya and rendering in Arnold. 

There's a super simple test model I created in Maya (the topology might not be perfect, but there are only quads, the shading looks ok, and there's no pinching): 

The low poly version: 

UVs:

This is the normal map that I get after baking in Substance Painter. I don't know how to deal with these seams.

- I tried with both hard and soft edges, and it seems that soft edges should be ok here.
- Also I tried cutting UV shells differently, but it does not solve the problem of visible seams - the seams just appear in different areas, but they are still quite visible. 

In Substance painter there is only one fill layer with Tri-Planar projection. The seams are hardly visible in Substance Painter:

However the seams look really bad in Maya.

Material in Hypershade:

- Base color: sRGB
- Metalness: Raw + Alpha is luminance
- Roughness: Raw + Alpha is luminance
- Normal: Tangent space normals + Raw 

And the render: 

So the problem is that seams are super noticeable in the final render (although I did not even know about this problem until I switched back to Maya, as in Substance Painter everything looked more or less ok). 

Could you please tell me what to fix in the first place? What am I missing? Thanks  

okidoki

Maybe have a look here :

https://polycount.com/discussion/232923/long-thin-triangles

gnoop

It's a well known limitation of ray traced  renderers  vs  game style rasterizing   like  the  one  in Substanse painter.     Ray tracing  just doesn't work together with normal maps same way.   You will always see  those artifacts in any offline  ray traced  render nowadays.   Nothing to do about it.   Even in games  "contact shadows"  which are form of ray tracing too instantly reveals those seams.

Its same in Cycles  vs Evee for example

DC74

okidoki said:

Maybe have a look here :

https://polycount.com/discussion/232923/long-thin-triangles

Ok, thanks! So basically I should try to avoid long thin triangles, right? In this case I need to improve the low poly model by manually cutting the tris, right? 

DC74

gnoop said:

It's a well known limitation of ray traced  renderers  vs  game style rasterizing   like  the  one  in Substanse painter.     Ray tracing  just doesn't work together with normal maps same way.   You will always see  those artifacts in any offline  ray traced  render nowadays.   Nothing to do about it.   Even in games  "contact shadows"  which are form of ray tracing too instantly reveals those seams.

Its same in Cycles  vs Evee for example

Thanks! What about the low poly in my case? Even if I get rid of the long thin triangles - will the seams be still visible? 

P.S. If I add more layers in Substance Painter (dirt, rust and so on), the seams are kind of hidden, but not gone. Don't understand what to do if I want to create a super simple texturing  (like just with the color, without additional "effects" like dust).   

gnoop

DC74 said:

 Even if I get rid of the long thin triangles - will the seams be still visible? 

Yes, they will be.    The seems in your screen is not related to thin triangles .    While thin triangles are not ideal   you can't get rid of them completely for low poly  game style  models.   But if you model for Arnold  offline rendering   you should use  quad only modelling  probably    and  use normal maps only for tiny hi frequency details on completely smooth shaded  model without split edges .    

  If it's for game model just ignore what Arnold shows  and preview it in something real time.   I used  Maya 20 years ago last time  but as far as I know  it should be  something  real-time there . Shader fx  maybe.      If you need a nice  game render style  picture use Unreal, Blender  Evee  or Marmoset, not Arnold .

ps. In fact  for such a model you need face weighted vertex normals  only.  I think Maya did it by default nowadays .  Such shaped model may need normal map to hide or make a rounding impression  for sharp /hard /split shading corners  . But since it doesn't have them   you don't need to bake anything .  

 

DC74

okidoki said:

Maybe have a look here :

https://polycount.com/discussion/232923/long-thin-triangles

Ok, thanks! So basically I should try to avoid long thin triangles, right? In this case I need to improve the low poly model by manually cutting the tris, right? 

okidoki

Seems to be also a "challenge" for different renderes.. never directly thought of this.. so thanks @gnoop .. i learnt something (almost) new today.. what you see is not always what you get 

gnoop

okidoki said:

Seems to be also a "challenge" for different renderes.. never directly thought of this.. so thanks @gnoop .. i learnt something (almost) new today.. what you see is not always what you get 

My guess it's a main reason why  Marmoset once got  extremely popular to do  game style renders .  Not Mental ray or Arnold . 

 Wish Marmoset  could provide same style  on-line shader node editor Blender does .    Plus some code export to show shader programmer  or to  chatGPT what you want.

For some weird reason there's no convenient one.  Working on the fly without compilation first .   

DC74

gnoop said:

DC74 said:

 Even if I get rid of the long thin triangles - will the seams be still visible? 

Yes, they will be.    The seems in your screen is not related to thin triangles .    While thin triangles are not ideal   you can't get rid of them completely for low poly  game style  models.   But if you model for Arnold  offline rendering   you should use  quad only modelling  probably    and  use normal maps only for tiny hi frequency details on completely smooth shaded  model without split edges .    

  If it's for game model just ignore what Arnold shows  and preview it in something real time.   I used  Maya 20 years ago last time  but as far as I know  it should be  something  real-time there . Shader fx  maybe.      If you need a nice  game render style  picture use Unreal, Blender  Evee  or Marmoset, not Arnold .

ps. In fact  for such a model you need face weighted vertex normals  only.  I think Maya did it by default nowadays .  Such shaped model may need normal map to hide or make a rounding impression  for sharp /hard /split shading corners  . But since it doesn't have them   you don't need to bake anything .  

 

As I am totally new in 3D, I did not even realize that Arnold is not the best (and target) solution for rendering models for games. Thanks again! 

So ideally the pipeline for checking a model would be something like this? 

- Maya (high and low poly)
- Substance Painter 
- Unreal/Marmoset

gnoop

DC74 said:

So ideally the pipeline for checking a model would be something like this? 

- Maya (high and low poly)
- Substance Painter 
- Unreal/Marmoset

I prefer  Evee  in Blender.  Quick  and  few  troubles  .  Best color management .     But if you work for Unreal  nothing beats Unreal.    

You can also try  iray  in SPainter    but it's half ray tracer  so this:

it reveals hard edges and Evee doesn't.       I actually not sure about  Mamoset . Haven't used it for couple years.   Also  iray  as well as other  ray tracing renders shows totally different intensity  of specular  reflections with same roughness texture .   As well  as Cycles,  Arnold ,  Octane, red shift    etc  . While all of them consider it physically based.      

DC74

gnoop said:

DC74 said:

So ideally the pipeline for checking a model would be something like this? 

- Maya (high and low poly)
- Substance Painter 
- Unreal/Marmoset

I prefer  Evee  in Blender.  Quick  and  few  troubles  .  Best color management .     But if you work for Unreal  nothing beats Unreal.    

You can also try  iray  in SPainter    but it's half ray tracer  so this:

it reveals hard edges and Evee doesn't.       I actually not sure about  Mamoset . Haven't used it for couple years.   Also  iray  as well as other  ray tracing renders shows totally different intensity  of specular  reflections with same roughness texture .   As well  as Cycles,  Arnold ,  Octane, red shift    etc  . While all of them consider it physically based.      

I tried Iray, and actually the result for my test model was quite ok there (and not ok in Arnold). The reason I exported everything back to Maya and tried Arnold is that I can configure the render scene there (light sources, for example), which I cannot do in Substance Painter.  

Currently I am using Maya; I haven't used Blender and Evee. Probably I'll try it later, for now I am just trying to figure out the basics.