Correct topology explanation for 3D displacement

[Morbid Angel]

Hey guys.
I constantly see people asking question: why does my displacement look odd, some parts look weird others do not, whats happenening?

And every time the answer is simple, your topology or the mesh is not correct, thus resulting in failed displacement.
So I desided to make a small tut to explain how to get that damn displacement right the first time.

Below are two images, one with displacement at work on something one could call a wall of the house with a window in it.
Object on the left has the correct topology needed for 3d displacement to produce good result, while object on the right has a typical boolean like mesh which one would normally get from programs like cad or elsewhere.

As you can see the object on the left has rendered correctly, while object on the right has not. The displacement has failed, due to surface's nsided polygons.





So, one will realize that such surfaces needs to be rebuild in order for displacement to work. Well then here are some tips on how you can rebuild the broken meshes and not waste much time:

make sure you dont have any nsided faces, or as little as possible.
make sure all your corners of boolean objects are connected to oposite corners of the mesh
once mesh has been cleaned up apply tesselate modifier with roundness at 0 and operate on faces option.

[paulison]

Thanks, this explains things quiet well.

say if i have a large building done in ArchiCAD (for example) that is made from nsided polygons (as you have shown), there is no easy way to fix up this mesh?

would just tesselating each object help?

[Morbid Angel]

brute tesselation wont do it, the initiat grid of topology has to be correct, all tesselation does is subdivides the polygon. Like meshsmooth only without smoothing.
This is such thing that one has to keep inmind prior to all major work, because it can end up in painful errors down the road. I would suggest fixing the topology only on those objects that need displacement.

[vlado]

I think Power Booleans have an option to re-triangulate any mesh in a form suitable for smoothing/displacement. Not sure if this will be included in the version for the 3dsmax subscription though.

Best regards,
Vlado

[R2J2]

With ProBooleans there's an option for quads and their size in percent, but I did a quick test and still getting some 3-sided polys in there. Tessellate does seem to work better, but Morbid your saying that there still may be errors with a mesh like that? it's not a neat as if I did it manually but there still all quads at least.

[Morbid Angel]

this needs further testing. but most important is not to have nsided faces, and random vertexes that float around. i will have to look into the probooleans thing to see.
Tessalate modifier is used for faces with large area. If an object contains displacement but does not have enough initial subdivisions displacement all will be incorrect. Thats why tessalate modifier is used.

[DaForce]

So basically you want the polys on the mesh to be evenly spaced out and with even density. And four sided.

[Morbid Angel]

yes, idealy, not necessarry to have them evenly spaced out, but this would be preferred.

[studioDIM]

Possibly also without triangle fans
Toying with normalise spline, extrude with grid capping, and meshsmooth, i got it working for the interiors of arbitrary splines capped.
What sucks is the border, triangulated,and the corners, which often exhibits triangle fans, and ruins the whole process

but the center works! XD

Lele

[DaForce]

cool , well that explains why my displacement has always worked

Im pretty anal about neat polys..etc..etc.

[Sawyer]

I just came into this same problem today. So what this means is that basically we can never use cad files and vray distortion. Is this correct? Because all of my cad files have the nsided polys where the fenestrations are.

[DaForce]

well you can certainly try to use vraydisplacement... but it just may not work very well/at all. And other than rebuilding the mesh or editing what you have to try and get as good a mesh as possible your kinda stuck.

[paulison]

If you use ArchiCAD and you are working with a large site mesh that needs grass displacement, check "all ridges smooth" on any mesh objects, then after importing into MAX apply UVW mapping, meshsmooth/smooth, then apply displacement. I know this is off topic but thought it may help ArchiCAD people with displacement issues

Will try Power booleans with the re-triangulate function some time, thanks for the tip vlado!

meshsmooth seems to work fine for me in large scenes anyway

[Arkitec]

formZ

Anyone out there have some suggestions for formZ. I usually export to 3ds. Is there a better way?

Thanks,

Arkitec

[Dynedain]

Re: formZ

Anyone out there have some suggestions for formZ. I usually export to 3ds. Is there a better way?

Thanks,

Arkitec

Don't use FormZ

Seriously though, we used to do all our modeling and rendering in FromZ. Slowly, with my prodding, we moved over to Max and started working with Vray. The other 3d guy here, who loved FormZ and hated Max at first, now loves Max, and won't even touch FormZ. Its such an antiquated piece of junk, and there are so many powerful things you can do in max that are virtually impossible in FormZ. I would highly recommend switching (and it will save you the cost of FormZ updates in the future).