Level Of Details (LOD) Seams etc.

Rhythem02

Hello there folks

I just want to hear your opinion and probably learn techniques about LODs.
I'm not new to LODs, but I want to hear you and probably learn.

Right now I'm creating 3 LODs with the following values 20K, 7.5K, 2.5K Tris.
-Do you guys care about appearing seams on second and 3rd LODs?
-Do you use different textures for each LODs?

Thanks!

Obscura

What kind of seams? Seams caused by the different model with the same normalmap? Or seams caused by the lack of edge padding?

Lods can depend on the art style... If you are using normalmaps, then the original model's normalmap obviously won't work perfectly on the lods. Some people ignore this, but some people use different material or at least a different normalmap.


If the given asset use complex shader, then its recommended to use a simpler one on the lod, maybe even an unlit one with baked-in lighting.

If the given asset use multiple materials and textures, then its recommended to merge them, and use only one mat/one texture on the lod.

Axcel

Generally about LODs from my perspective:
I start with assumption that subsequent LOD should have 1/2 tris of previous one. It could be more or less, depends how much visible is transition.
The main 2 things which are imo most visible during LODs transition is:
- change of smoothing
- change or object's silhouette
So I am trying not to interfere into it as much as I have to.
What i do is obviously removing loops, extrudes, small details, especially from center of the object. Keeping in mind from what angle object will be visible from far I remove i.e. geometry from inside of holes, geometry visible only from top. Even places very near to the ground most likely will be covered by something and could be easily simplified.
If there are small elements like i.e. flowers/fruits on a plant, using separate texture and material it is beneficial to remove it on LOD.

a3D

How do LODs interact with drawcalls?
Could they actually hinder performance if done wrong or is it a non-issue?

Rhythem02

Obscura wrote: »

What kind of seams? Seams caused by the different model with the same normalmap? Or seams caused by the lack of edge padding?

Lods can depend on the art style... If you are using normalmaps, then the original model's normalmap obviously won't work perfectly on the lods. Some people ignore this, but some people use different material or at least a different normalmap.


If the given asset use complex shader, then its recommended to use a simpler one on the lod, maybe even an unlit one with baked-in lighting.

If the given asset use multiple materials and textures, then its recommended to merge them, and use only one mat/one texture on the lod.

They way I do LOD, I only use one set of maps across all LOD. Reducing the Highhest LOD to Mid LOD there comes a point where you have to reduce the vertices/triangle near a seam. So what happens is the seams becomes visible.

So I'm asking if you guys are bothered by it. If some seams are a bit visible for the Mid and Low LODs. "OR" Do you guys use different sets of maps for each LOD, like reprojecting.

Obscura

Personally I like to use own normalmap at the lod.

Can you show an image, so we can see if the seam is very visible?