Really need help!!

[skdzines]

Can someone please help me!?! I am fairly new to all of this zbrush to maya workflow and pretty much everything else. Basically I have created a genie character that is supposed to look like he is made of marble. I believe it has pretty good topology but I’ll leave that call up to the experts on this forum to tell me that. I have laid out my uvs using hydralabs pelting tool for Maya. Exported the obj, then imported back into zbrush successfully without exploding, and then created my displacement map, normal map and color map in zbrush. They are all 2k tif files converted to .map files.

I have followed some of the other threads for displacement mapping in external renderers so I think I have a fairly good understanding of it. Anyway, when I use the approxmation editor for mental ray, I get a descent displacement but there are some issues, especially with the fingers, finger nails and ears. Also, it seems that when displacing, my color map loses a lot of detail. Can anyone explain this? I have posted several pictures of renders from maya, screenshots from zbrush of what it should look like in maya, uv layout, maps and an image of my topology. I am also getting some seams as you can really see in the image of the hand, but I also am getting a slight seam down the front of his face at certain angles. I have redone the uvs about 20 times now to try and eliminate the seams, which this is the best so far, but I’m not sure if there is a better way. It is hard to put them in places that they won’t be seen because he doesn’t have a shirt on.

I really hope someone can take a look at these and give me some pointers as to how to correct these issues.

System specs:
Vista 64
CPU: 3.0 ghz quad core
8gb ram
1gb video card
Maya 2008 sp1
Zbrush 3.1

Attachments

[chris-carter]

Well, I’ve not done this task with maya much, but I have with 3ds max. For one thing, you should be able to eliminate the appearance of seams using ZBrush by virtue of the fact that ZBrush calculates all that without the need for you to think about it (vs hand painting a texture where you do need to think about it). So I wouldn’t waste any more effort there.

Now, about the displacement, someone more knowlegable will need to weigh in here to apply this concept in maya, but for successful displacement, the renderer needs to know where the 0 point is on the map, so in max, you need to adjust the output values of the displacement map so that mental ray knows that 50% gray is the 0 point (the place from which to begin displacing out and in). This is because max sets the low end at 0 and the high end at 1 by default, so in max one has to set the low end to -1 and leave the high end at 1.

Another thing about displacement is that you need to be sure that in ZBrush, a displacement map would be pushing straight in or out from the surface. That is, you can’t expect a displacement map to push polys around turns or something. This is why a displacement map will be most effectively calculated and applied using a sub-D level closer to the one that you want to achieve the look of via displacing. Typically getting a good straight in and out displacement is done by completing your sculpt, then retopologizing (transferring the detail to a new mesh with better topology). Given the topology you’re showing here, I’d say you need to perform a retopo.

Third thing on displacement is poly resolution. Poly resolution will help determine your quality of displacement. In mental ray, this takes place on two levels, one is the resolution that you see, which you increase by subdividing. The other is the additional subdivision that is applied for the sake of the displacement process, which can be made visible by doing a wireframe render. This second level of subdivision is important because you can adjust it in mental ray to help improve render times, and the appearance of the render. It can be difficult to understand though because it’s referred to as ‘edge length’ where the name ‘edge length’ can have two different meanings.

a. when view-dependent is on it specifies the length of each edge in pixels.
b. when view-dependent is off it specifies the length of the edge in world space units.

So…isn’t this all for 3ds max? No. it’s should apply to any displacement done using mental ray.

Given what I’m seeing here, I think you should make sure you’ve specified the correct 0 point for the map in maya.

I’m sure there’s a simpler way to say this stuff. Say so if you need clarification . And could someone with a better maya knowledge please chime in on this?

[skdzines]

thanks for the reply Chris. I will attempt to retopologize the mesh. Hopefully it will clear up some of my issues.