Geometry stretching when applying surface noise : making sense of the issues

Moutrave

Hey all,

I keep coming accross that stretching issue when I apply a surface noise on a mesh in Zbrush. Now I know that most of the time this is caused by a lack of definition in the original mesh, not enough tesselation or a not-so-clean edge flow. Still, I've been checking and rechecking my meshes, which are very simple I might add, adding more edge loops, tesselating them, adding more geo etc, and that issue still happens. I have to subdivide like crazy in zbrush for the stretching to stop happening (around +6 million polys for a dumb test object).

Now I've tried applying surface noise on very low poly objects made by other people (like the orc made by Stephen Wells in a 3D motive tutorial), that originally did not have as much tessalation as my own objects. And the surface noise worked perfectely when applied (with only so much as 2 millions polys, as opposed to the 6+ I need) so there must be something wrong about my stuff...if anyone can make sense of what I do wrong I would greatly appreciate it as i don't really know what to change anymore to make it better.

I've enclosed some screens of one of my objects, which is like I said, a very basic piece of geometry. I'll list them here :

1) base mesh as it looks coming out of max (around 1000 polys)



2) With around 2 million polys in zbrush



3) surface noise not yet applied to mesh



4) and the noise once applied and the stretching it provokes.


Thanks in advance for the help !

Moutrave

Actually I realize that the issue is kinda subtle on the previous screens, so here's another object with more serious issues

Weird on this one is that the stretching does not concerne the whole surface. Could it be that my tesselation is not even enough in some areas like the middle triangle?







Thanks again

Quack!

Uneven distribution of the polys could be the issue. Any reason you aren't using dynamesh to get even distribution?

Bubba91873

I come across the same issue when applying noise in zbrush. I typically use a lot of thin meshes with holes in them. Dynamesh wants to close the holes when it does its thing and that's not what I would want.
Zremesher behaves better for even quads for me at least in these situations.

On Badkings website he advises to use the morph brush and store morph target when you use extreme noise in the graph editor.
http://www.badking.com.au/site/tutorial/understanding-zbrush-noisemaker/

Moutrave

Quack! wrote: »

Uneven distribution of the polys could be the issue. Any reason you aren't using dynamesh to get even distribution?

Hey,

The reason is...that I just never used Dynamesh. I thought it was used to create objects from scratch and I wouldn't know how to use it in that cas. Also those meshes I made were created and UVed in max and I thought Dynamesh needed retopo because it would mess the UV's...but then again it may be just the misconception of a beginner.

But i'll see what i can do and gather some infos !

Moutrave

Bubba91873 wrote: »

I come across the same issue when applying noise in zbrush. I typically use a lot of thin meshes with holes in them. Dynamesh wants to close the holes when it does its thing and that's not what I would want.
Zremesher behaves better for even quads for me at least in these situations.

On Badkings website he advises to use the morph brush and store morph target when you use extreme noise in the graph editor.
http://www.badking.com.au/site/tutorial/understanding-zbrush-noisemaker/

Thanks Bubba, I'll take a look at badking's site, hope I can finally make sense of that noise thing.

Moutrave

So I added some edge loops around and it works better in zbrush...I just didn't think I would have to go to those lengths for a simple mesh and that regular zbrush subdivision or max turbosmooth would be even to have even quads.

I hope it's ok though if I remove those edge loops for the final model and just apply the normal map I made from the heavier base mesh...wouldn't want to have some many loops that this simple object does not need.



The badking video is great ! He doesn't really talk about stretching but that morph brush tip is guaranteed to come in handy sometimes; Good stuff.

Quack!

Ok, so use dynamesh if you continue to get stretching. You want your models to have the same poly density across the entire mesh. Dynamesh will do this. Just take your current triangle shape and run dynamesh on it, play with the various settings to see it's effects.

Moutrave

Quack! wrote: »

Ok, so use dynamesh if you continue to get stretching. You want your models to have the same poly density across the entire mesh. Dynamesh will do this. Just take your current triangle shape and run dynamesh on it, play with the various settings to see it's effects.

Thanks i'll be sur to do that as soon as I get home didn't know Dynamesh did that it's pretty cool !

Ghogiel

everyone has this happen eventually. A few times it's applies nearly perfectly. Other times its all kinds of fubar. Only way I know is using the morph target switch on the low subd level to minimize it. I still think it's kinda hacky way to do it and not a proper fix/

http://www.polycount.com/forum/showthread.php?t=111024