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View Full Version : How to use Zbrush displacement maps in mental ray(3dsmax)


MikeNash
09-16-2004, 03:17 PM
Anyone can help me out on how to use Zbrush displacement maps in mental ray using 3dsmax version ?

I have used 3dsmax displace but using that you have to subdivide your model up alot and realy lags it down.

I just want the results when it renders out.

plaguelord
09-16-2004, 04:19 PM
you can`t use vray? I really fast and simple.
Edit Mesh, Meshsmooth 0x3, Vray displacement mod.

MikeNash
09-16-2004, 04:27 PM
I can try

Where can i get Vray displacement mod ?

What you mean by Meshsmooth 0x3 ?

plaguelord
09-16-2004, 10:50 PM
The Vray Disp Mod comes with Vray Render, on the vray site you can download a free demo version, I dont know if it comes with displacement.
Meshsmooth 0x3 I want to mean, 0 on viewport, and 3 on render, so you can keep you viewport fast and only calculate the subd on render time. You can export the 0 level subd model from zbrush to max, with the hires disp map tiff.
In the forum I started a thread called zbrush and max displacement, there are some info to beginner, (like me), and I finish a tutorial in this area. I will post the link soon.

primal101
09-16-2004, 11:13 PM
i don't have Vray, so what other option do i have beside using displace modifier.
:cry:

Kanga
09-17-2004, 12:45 AM
Vray is a render engin that came with Max5 if you want it for Max6 you will have to use the demo version or buy it.

Over in ZB central there is a long thread on just this. http://206.145.80.239/zbc/showthread.php?t=020310

This is a bench test with one model and contributors are invited to test the zB displacement with their outside apps and render engines.

Sift through the thread it is well worth it.

If you are like me then you have Max6 and two engines to choose from, scanline and mental ray. So far I have only gotten results from the scanline engine using an applied material. If you want to know how to do it then visit my mini tutorial here http://206.145.80.239/zbc/showthread.php?t=17565&highlight=Great+displacement

Kanga

Sully
09-17-2004, 04:28 PM
Hey kravit its easy! import the base model in from zbrush, add a meshsmooth and check the smooth box that is for render time only (I set mine to 4 itterations) on top of the meshsmooth add a displace modifier and make sure you check the use original mapping coords, add your displacement map that you created in zbrush into the map slot. Instance it into the material editor, go down to the output rollout- enable curve and drag the point on the left down to -1 and leave the point on the right at 1 and then tweak the strength until you get identical results as in Zbrush, I can get identical results using this method :buttrock:

P.s any chance of some help with Shaghair?? :)

Kanga
09-17-2004, 05:03 PM
Sully!

Your avitar breaks me up!
Always has.

Kanga
09-17-2004, 07:12 PM
Sully tried your technique couldnt get it to work so a couple of questions.

add your displacement map that you created in zbrush into the map slot
There are two slots: bitmap and map, which one do you use?

Instance it into the material editor,
Under utilities menue in the material editor you can only instance a map if it is used on duplicate materials. How do you go about instancing a map in the case there is only one copy?

Do you have to enable displacement under elements?

If you are using 4 literations how long on average does a render take? I did a simple head model test and with a P4 3Gig processor, my computer hadnt turned out a result and was still churning after 30 mins. If the renders take this long it would be ok for a still image but a nightmare for an animation.

Thanx for your info so far, hoping you can fill in the blanks.
Kanga

Sully
09-17-2004, 07:44 PM
You have to put it in the map slot below the bitmap slot (I dont think it makes a difference though it works both ways) Once you have got your meshsmooth and diplace mod in your stack add the displace map to your displace mod, once there drag it into a slot in your material editor, go to the output properties for that map, on the little graph drag the left point down to -1 and leave the right one where it is at 1 and then tweak your strenght gizmo in the displace mod to get the right balance your looking for( you can view the outcome in the viewport simply by upping the meshsmooth itterations). The renders take no time at all about a min or two because you not really reallying on the render to do the displacement its the modifiers within max that take care of it.:thumbsup:

RazzMataz
09-18-2004, 12:01 AM
Hey Sully, thanks for that method, it works great. What is interesting, that after rendering a scene in Mental Ray, taking 2 and a half minutes, then switching to the default Scanline, the same scene took 18 seconds to render. At 4 meshmooth iterations.

I do believe that Kanga was talking about using Mental ray's micro-polygon displacement features, which I have not got to work yet with z brush properly. The reason is probably because mental ray takes into account the white/black values of the map differently than what z brush spits out by default. E.G, (scaneline) a value of 50% gray means no displacement, black is negative, white is positive.

With MR, black is 0 displacement, white 100% displacement, and to go into negative values, you need a seperate color channel or something. (I'm not entierly clear on this...)
The z brush tuts take this into account, and give insructions on how to modify the map to suit render engines like Mental Ray, but I have not got it to work yet, most probably because I am missing steps here and there.... Mainly it is the use of the map in the new MR material settings which I do not understand fully yet.

Anyway, enough rambling, and thanks again for that info on using the displacement modifier, I should be able to see good translation results from z brush to max using this method.

Cheers.

Kanga
09-18-2004, 01:20 PM
Sully

HOLY CRAP!
THATS FAST

Thats what I bought ZB for.
Thanx for your further directions, you just saved me about a zillion hours of hard work. With 4 literations and the scanline renderer my hed test was done in about 45 seconds.

Couple of things I noticed:
Apearance of a few tiny holes in the end render, small price to pay for the overall effect though.
Max tends to go to sleep after test render so I have to click once in a viewport to wake it up. Going to do an animation test now to see if this is a problem for sequences.

With your method I can use a fairly low mesh to achieve a high res result:thumbsup:.

RazzMataz

Reading as much as I can on this subject and my general impression was that micro poly displacement wasnt supported in Max. I could be wrong though. Let us know how your testing pans out. I am extremely interested.

Once again THANX guys,.... you made my day!

Kanga

RazzMataz
09-20-2004, 05:34 PM
Hi Kanga;

With regard to the micro-poly displacement comments I made before, I was refering to Max 6, in which Mental Ray is now included as an alternate renderer. If you switch to MR from scanline, you have access to micro-polygon displacement. (I should have mentioned I was using M6.)

So tiny holes appeared on your mesh after completing a render? Interesting, that is a problem I associated with Mental Ray's displacement, based on tests I have done so far.
Using Sully's method, I had no seams or holes on my test mesh after rendering the displacement in scanline, (a fairly detailed and complex model of a dragon.)
Perhaps it is the way your mesh is modeled? I'm only guessing of course, but if your mesh has uneven topology, such as large areas of non tesselated polygons, with tri's in strange places, at render time the displacement might go a bit wonky. Or it could be a smoothing group issue.

Any ways, good luck with your work.

Cheers.

Kanga
09-21-2004, 01:17 AM
Hi RazzMataz

I haven't tried Mental Ray yet as I am new to both Max and ZB and there is soooooo much to learn. All the examples I have seen so far with MR have been kind of grainy so Im sticking with the scanline at the moment.

You are right about the mesh though, there are no tris but there are uneven quads (oblongs) in some places and this is where the holes occur.

Thanx for your kind wishes on my work.
Kanga

MikeNash
09-21-2004, 06:24 AM
Yeh,thanks for help guys
Yeh i wont be able to render in other programs until i upgrade, need more ram to do it.

Yeh, I don't realy know how i can help with shag-hair.
Just keep working on it, no tricks to it ,just hard work.

Sully
09-21-2004, 09:44 AM
This is off topic so I will keep it brief.The im biggest problem is getting the Shaghairs to go where my splines are going they seem to have a mind of there own?? Can you give me an idea of how many Modal hairs you used? That should send me down the right track I think I currently have about twenty and a hair cut that looks like mine in the morning!

MikeNash
09-21-2004, 10:00 AM
Hey,

I used something like 2500-3000 splines

Mess around with auto influence amount aswell
as all other little settings in your modifier for shaghair

Sully
09-21-2004, 10:59 AM
SHIT!! Thats alot of Modal Hairs, are you giving each one there own id or bunching those turkeys together..

MikeNash
09-21-2004, 11:04 AM
bunching, that hair was made up of something like 25 layers
I done this to get alot of control over the hair and to let computer run fast

Sully
09-21-2004, 11:18 AM
Cheers Kravit!!

eks
12-29-2005, 02:16 AM
The key is under RGB Offset value in the Output rollout of the Material Editor:

http://206.145.80.239/zbc/showpost.php?p=139317&postcount=88

If you set it to lower than 0 (like -0,5), it may work.



eks

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