VrayFur extreme rendertime

[fAEkE]

I'm rendering a car interior and been asked to take the materials to the next level, and therefor I've begun to try VrayFur for the interior carpets which we have never used before.

I'm new with VrayFur so I have no idea how consuming it is to use, but the rendertimes for my scene is extreme when applying fur to only one of the carpets. The scene has about 10 arealights and one spotlight, and renders with no problem at A4 400DPI without fur. When I apply fur with default values (0.2 units per area) the lightcache wont even begin.. it's calculating and the estimated time increases. I stopped the render when estimated time for lightcache was at 250 hours.

The carpet geometry is fairly lowpoly cad (editable mesh). I use IR map medium 50/20 and 1500 subs lightcache (glossy rays with light cache aswell). Nothing out of the ordinary. 20 subdivs per light.

[squeakybadger]

Haven't tried VrayFur in years. Have you tried it with the VrayDisplacementMod instead? I always find that fairly useful and quick to render.

[fAEkE]

I think I have found the problem, already. But it rises another question.

The problem seems to be that the mesh has a couple of small polys that will get a very large amount of hairs campared to the other faces. Is there a way to fix this without modelling the carpet? The mesh is cad as I mentioned, and some faces are very large while others are very small.. I guessed that "per area distribution" would fix this but I was wrong.

[fAEkE]

@squeakybadger
No not yet, the carpet is closeup so I'm guessing displacement wont do the trick, but it seems that I have to try it since we don't have time to remodell the cad geometry.

[super gnu]

as per your thread on displacement, putting a subdivide modifier on the geometry to be furred and making sure you have nice small polygons by setting the subdivision amount to something sensible can massively speed up rendering.

its all mentioned in the spot3d help pages...

[fAEkE]

Yepp, but I still have the same problem as in the displacement thread. We can't modify the mesh

[vlado]

Have you tried increasing the dynamic memory limit setting?

Best regards,
Vlado

[3DMK]

Yepp, but I still have the same problem as in the displacement thread. We can't modify the mesh

WHAT DO YOU MEAN???? You can't change the mesh.....is this for real...have you been told to not touch a vertex by the client or he/she will sue you????

Max Subdivide is a simple modifier....takes 2 seconds to slap it onto a mesh & as the guys said...your problems will be solved

Subdividing is not changing the mesh outline or shape in any way--- only internal subdivisions.

****I come accross similar stuff all the time....You have to way up ALL your options.....you may actually take longer trying to work with your bad mesh than building a new one or modifying it. CAD models suck big time!!

Hope this helps

[fAEkE]

@vlado
I'll try this when I get some time over for testing, thanks

@3DMK
I'm allowed to change the mesh regarding amount of polygons yes, but as I have said before, when we apply modifiers to the mesh the normals flip. When you import cad info and change it to a mesh, the application we used to convert the mesh sees the normals with the help of the cad curvature. When you export the mesh and import it to max, the original curvature is lost. The mesh normals looks good when imported to max, but if we change anything (add a modifier, change to editable poly, tessellate in editable mesh) max needs to calculate the normals again. And without the original curvature, some normals will flip.

"****I come accross similar stuff all the time....You have to way up ALL your options.....you may actually take longer trying to work with your bad mesh than building a new one or modifying it. CAD models suck big time!!"

CAD sucks yes but the cad works fine if we don't use displacement and fur which need a better mesh. We just have to use bump and no fur right now because we don't have time to remodell the mesh.

Too bad that fur needs a mesh with the same polygon size all over it... I don't understand how this can work proparly for anything tbh since no mesh is perfect. Or am I missing something?

[super gnu]

fur doesnt need a mesh with the same size polygons all over.. it just doesnt like big polygons. and adding the subdivide modifier, as mentioned, fixes any problems, and doesnt affect the model in any other way, so tis not a problem (unless you have a really bad mesh) ive never heard of it flipping polygons to be honest. sounds to me like whoever is exporting has "2 sided mesh" ticked and your getting double polys for every surface.

[fAEkE]

But I still don't undestand how it works. Per polygon is obvious, but per area doesn't work the way I want it to.. The mesh consists of alot of different sized polygon as you have understood, but the small polygons get alot more hairs than the larger ones.. in my eyes, thats not the way per area should work.. should be the other way around.

I'm no expert in meshes, and these meshes was made a couple of years ago, before my time on the company. All I knwo about it is what my colleagues have explained. There is no way to fix it as far as I know. I'll see if I can post some screens for you, need to ask my superior first.

[super gnu]

yes that is strange as per area should work.. per area! however if those polygons are actually double faces, youd get twice as many hairs there? just a thought.

[fAEkE]

No they are not double. Here is a print for you guys:

[super gnu]

can you do me a favour and do a screengrab of waht happens if you just stick a "subdivide" modifier on the base mesh, with a nice small subdivison (i never use tesselate, as subdivide makes a much nicer mesh) also did you check your vertices are welded? if u can send just that mesh object i could take a look

[samuel_bubat]

Seriously, using a CAD Import for Displacement or VrayFur is most of the time just a huge headache.
I would just detach and remodel the area for diplacement by hand. It looks like simple geometry anyway.
Also if you wanna prevent such messed up normals as seen in your screenshot, add a "Turn to Poly"
modifier before adding an "editable poly" mod and activate "limit polygon size" with a value of 3 or 4.
(3 is probabely better)

cheers