Displacement GI

[super gnu]

ahh good luck.. yes i didnt mean to sound like it was a rare case to get a bad mesh... hehe ive spent half my career cleaning other peoples bad modelling. but it was the total un-editability i was wondering about.. sounds like linked / referenced geometry issues. all i can advise is to have a word with whateer clients are modelling and sending stuff.. ive had great improvements when ive asked regular clients to avoid certain things when modelling (double faces for instance) and worked out a good import/export workflow with them at the start of a job.

[super gnu]

yes ive imported thousands of model at all levels of complexity.. what software are you getting the models -from-?

[fAEkE]

Same here, I've worked with loads of bad meshes, but in those cases it was poly-modelled meshes, and thats a different story. The mesh we got now was imported to Opticore Opus Realizer and tessellated to a mesh from the original cad. When we import it to max we no longer have the original cad to calculate the normals, so if the mesh is to low poly, which it is in some places, some normals get flipped when edited and the mesh looks like a chessboard (black and white)..

[super gnu]

lol ok obviously i didnt have quite enough experience.. never even heard of opticore opus realizer :P one thing i would say though, is if you are talking about nurbs or csg models (from microstation rhino alias catia etc..) then i cant recommend npower power translators for max enough. they read rhino files natively and also import iges / step / sat files (plus dozens i never heard of) and bring them into max as clean nurbs models. since the npower software has its own extremely powerful nurbs system, you dont need to go near the horrible max ones. you then have a model that you can either adjust tesselation until you are happy and then simply collapse to a mesh, or keep as nurbs and take advantage of view dependent rendertime tesselation.

p.s. if you do try it, have a go at their nurbs booleans and filleting.. works like a real charm.

[fAEkE]

Thanks for the tip. We have talked about importing the cad to max that way, and it sure would be better, but we can't do it at the moment because our company is not responsible for the geometry. It's complicated

[super gnu]

isnt it always :P

[fAEkE]

Indeed

I was able to subdivide the geometry, as you have seen if you followed the fur rendertime thread, but I still have huge problems with the displacement.

When using Vraydisplacement modifier and 2d mapping vray doesn't presample the displacement, or it's so fast that I'm not able to see it happen, but the mesh breaks if I use the modifier on top of subdivide so thats not an option. I tried to use displacement in the material again and presampling displacement just goes on and on and on....

Low IR preset 30/20, 500 LC. 2/5 DMC.. nothing special, all else on default. A couple of arealights which have 20-30 subdivs. The only change I've made for vray displacement is unable Relative to bbox and set amount to 1mm.

I also tried dynamic memory 6000mb, no change.

[super gnu]

if youre using the displacement in the material, check the settings in the vray system settings -default displacement -window, or set a displacement modifier to 3d and "use object material" then you can control quality there. depending on your render, you can probably adjust the min edge length to something bigger than 2 pixels. also the max subdivs can be reduced in a lot of cases. (the smaller your polys are in the source mesh, the less subdividing the disp. modifier has to do. so if youve subdivided down to 1 cm (not recommended but a balance where you subdivide as much as possible then drop your disp quality to compensate will help.) then you only need a few subdivs in the "max subdivs" section.. if its one huge poly, youd need to crank this up and the displacement will be working super hard.

also, yes 2d displacement will break unwelded meshes, and to be honest, so will 3d displacement although not so bad. really to use displacement you - need - good welded meshes.

[fAEkE]

Ye I've been working with the Vray: default displacement settings but nothing seems to work. I've tested really low settings, but presampling still takes forever.

The problem with the modifier isn't that the displacement breaks the mesh, but the modifier itself. As I've described earlier, I can't use most modifiers and I can't change the mesh. Still, why doesn't vray material displacement work? The mesh is crap, unwelded, and I can't do anything about it, but it worked fine with 2D displacement before I subdivided it.. even tho it took lon time to render.

Might the problem be that 3d displacement dont work with unwelded surfaces?

This is a mess.. I would need more time to test. But it seems that I have found the solution for fur so I'll quit displacement for the moment. I'll post about fur in the other thread.