How to get 3d displacement as crisp as 2d displacement

[thablanch]

Hi,

Been spending quite a few hours on testing (and forum search of course).. so here is the question

I'm doing some tires sides, and some displacement is needed. The text is (in real live) cut very sharp. The source map is very sharp as well.
When I use the 2d displace, the result is great. It renders fast and it is amazing.

However, as the tire has 2 sides, and the displacement needs to be correct each side, I must use 3d - with use object material, and using a multi-sub, I have one for each side of the tire
The 3d displace result, using sharp map, high subdiv, small edge length, is really not good, kind of roundish and soft, and way longer to render.. soo long. A preview takes like 10 min vs 25 sec for 2d. - when not crashing because enough ram.. an I got a sweet little machine
Subdiv gives some bad results, as it smooths zones that are not supposed to be smoothed.


Any tips to get this working fine??

thanks!

[Joelaff]

Assuming you have your displacement settings up high enough to get the needed resolution did you try VRayHDRI and check the different interpolations type for the map? (Note elliptical does not work with displacement right now, at least I didn't get it to.)

http://docs.chaosgroup.com/display/V...ationParameter

You have your displacement map in an uncompressed format too, right?

You are using the VRayDisplacement modifier, or displacement in VRayMtl? With the modifier you could try turning off Filter Texmap, or lower the filter blur. I assume you have your edge length at something around 1.0 or less.

[thablanch]

Strangely, I had better results with compressed files for this particular use, and I can not go under 1.0 for edge length, cause the computer crashes..

Vray displacement modifier, as I need a control of the height, tried all filterings..

I'll give the VrayHDRI a test, as this seems to be the only variable I did not try yet!

Thanks for the advice

[thablanch]

The HDR best test seems to give slightly better results.... Thanks Joelaff for the input

Not quite there yet

1 - regular 3d disp.. best edge length I can have with my computer surviving
2 - with HDRI, best result of filtering
3 - 2d displace, best results, dut can not use it for continuity issues around the tire..

[Joelaff]

I am guessing it is a clean mesh, all quads... Perhaps try tesselating the base mesh more? (Like more turbo smooth if you are using it, or a tesselate with smoothing zero.)

You tried lowering the blurring of the texture both in the bitmap/VRayHDRI node and the displacement modifier, right? I don't recall if the one in the bitmap/VRayHDRI node affects displacement, but I think it might.

Maybe out your map on a simple plane in a new scene and get it working there first. Maybe some scaling or something is affecting things.

[thablanch]

Geometry is not that clean.. but not bad.. But some other tires are really clean and I have the same issues
Tried playing around with blurring everywhere as well

I'm exploring a workaround with 2d.. kind of getting there with multiple tiles in composite ( thanks Neil !)
http://www.neilblevins.com/cg_educat..._uvs_tiles.htm Still a few glitches on the treads now, but getting there I hope.

Lets say it is an interesting challenge

[Joelaff]

Aren't your textures in their own map channel and f filling up the 0..1 space? I usually just use another mapping channel rather than mess with UVs outside of 0..1.

Were your original displacement maps outside of 0..1 ? I thought some features did not work right when you did that. (I could be wrong, really I just use multiple maps because I think it is easier to tell what is going on when you come back to the project months later, or hand it off to somebody else.)

Anyway, I too have always gotten sharper results with 2d. I usually start with it, and am amazed at how well it works. So much I read claims it uses more memory, but 3d always seems to use tons more memory at the quality levels I need. I have to turn the edge length down too low.

[thablanch]

The Multiple maps was not working for this use.. but the multiples tiles did.. first time I was using it for a real production purpose..
I Agree with you on the 'not as friendly' way of using this.. And I'll need to document it for other members of the team (or me in a few months) when we will have a rework

I'm quite happy about the way it turned out..

[Joelaff]

Glad you got it working. So that is 2d displacement in that image? Looks great.

[Morbid Angel]

There is no reason 3d displacement couldn't handle this kind of detail. What is your max subdivs at? Typically you want to keep them low like 4-12, and control the detail with view dependent edge length, lower the edge length for better quality *but not too low.

[artmaknev]

Maybe your object's normals are messed up, have you tried resetting the Xform?
In the Utilities tab - Reset Xform (click twice) - convert object to edit poly, and try the 3d disp again.

Also, what are your PC specs, not sure why its draining so much ram, doesn't look too heavy.

[thablanch]

Hi Dimitry

Tried quite a few things with edge length and subdivs, but I never was able to get such good result as 2d. I totally agree with you, I wanted to keep this 3d as the documentation also states that now 3d displace is better and faster.. Too short of an edge length kills the computer nearly all the time. For subdivs, I tried many things, but then again seems to stall. However, this is probably the place where I will continue testing
All the prod is done in 2d now, but I'll go through an other phase of test, as I want to get this working in 3d as well.

artmaknev.
Got quite a big computer, and really stable nearly all the time
I7-3930 (so 12 cpu)
32. GB of ram

I also have to think that this needs to go trough the render farm, and some of our machines 'only' have 16GB, so the scenes must be compliant.

Reset Xform was done, and was also done with our custom in-house reset xform tool that works well (not that we do not like the regular one, but we do not like the regular one.)

Thank you guys for the replies.. I'll give the subdivs an other try.

[Mnietek2707]

Have you tried 16-bit grayscale bitmaps slightly blurred in photoshop with filtering in max lowered to 0?

http://forums.chaosgroup.com/showthr...051#post392051

[Morbid Angel]

can you post that tire with the displ map for us to try? Generally speaking though, really fine displacement at the point where you see letters is not going to be low, but it shouldn't take that much ram.