ZBrushCentral

topology projection problem

ZBrush Usage Questions
#1

Hey guys,
I have a high rez detailed mesh and a low rez version with a different topology that I am trying to project the high rez on to.

The problem I am having is, that it turns the low rez mesh inside out and takes the corners to the opposite sides of the mesh.
I am using the default settings for projection, but no tweaking seems to do anything.
I checked the normals in XSI and they all see to be pointing in the right direction.

The ultimate goal is to project the high rez detail on to a game ready model, but I can’t get the high rez mesh in to MAYA without crashing, and XSI crashes when I try to interpolate a normal map from the two objects.
So I thought I would try to create the normal map in ZBRUSH, but I need to use the geo and uvs from the low rez. And now that doesnt seem to be working.

Any ideas, …aside from a beefier computer…

#2

It sounds like some of the “rays” from your projection tool are missing the low res model. If you post some pics and your steps, someone here can probably help you out. If you’re on a PC, you might try a different ray scanner/map generator like xNormal (www.xnormal.net) to see what that gives you. Since your topology is different, your UV’s are also probably different as well, so you might have to make your low-res model a little “beefier” (e.g. inflated.) so you don’t have as many ray misses when generate the map.

HTH,
-K

#3

Thanks Kerwin,

The steps I am doing are

Make a zsphere
point the rigging roll out to my High Rez mesh.
Import my low rez cage, which I have done as you suggested, inflated a bit so that the high rez is just a bit inside and no intersection occurs.
Point the topology roll out to my low rez mesh.
Project
and then preview with adaptive skin.

The low rez mesh has the uv’s, the high rez has none.
The object is basically a door frame, and it takes one side of the frame
and moves it to the opposite side, turning the mesh inside out.
The highest level of projection looks fine but then every other level is a mess.

#4

I did try to manually build over my high rez mesh in Zbrush for grins, and that seemed to work much better. So all I can think is that some tranform or export is not seeing the mesh right, like it thinks the normals are inverted or its flipped or something.

#5

Turn down the projection strength ( or is it distance ). If set too high, points can shoot through and get mapped to the other side.

#6

Two thoughts occur:

  1. Fiddle with the project range slider on the Projection subpallet, including going all the way to -1 (to the left) to see if this helps.

  2. Try projecting mesh details by alternate projection technique using subtools. You make the high res a subtool of the low res and use the “project all” button on the subtools pallet. Sometimes, you can improve getting the details projected by projecting your high res’s level one, then level 2, and so on, projecting one level at a time (just you the detail silder on the geometry pallet.)

HTH,
-K

#7

tried that with little luck, thanks.

Kerwin, thanks, I will try the Subtools method next that you mentioned.

I guess what I really want, is to extract a normal map based on another meshes UV"S. That would circumvent all this rebuilding stuff…

Max, maya and XSI all have tools to do this.

Does Zbrush have this ability buried somewhere, that I am missing.

Thanks.

#8

I think you need xNormal for what your describing . . .
-K

#9

Thanks Kerwin, the subtools method worked splendidly.

I am looking into the normal map utility you suggested as well.
Thank you for the help.

Still kind of perplexed that the normal map extraction can’t be based on a different mesh.

#10

Zmapper may be able to do something more in normal map projection, but since it isn’t on my Macs, I don’t use as much as I use xNormal (which I find gives me splendid normal maps.) ZB’s mapping strategy is in general one of UV subdvision. It does provide for loading a new level one with new UV’s which it will subdivide to the highest resolution. It’s my speculation (since I don’t have visibility into the code itself) that it uses these matching UVs from high to low to better align the raycasts to compute the normal map. Other bakers, such as Modo’s and xNormal can use a spherical raycast technique and “nearest surface” techniques to align the raycasts along the low-res model’s normals. xNormal also has a UV matching algolrithm now, which I suspect is similar to zmapper, where the matching UVs high and low allow the direction of the rays to be better focused and give you ultimately a better map for SDS-style micropoly displacement or similar rendering technique.

-K

#11

Thank you Kerwin,
I just tried the Xnormal utility, and it too worked fantastic. Exactly what I needed and more. Thank you a ton for your help.
I hope this post helps someone else with similar issues.
Ormon

#12

Glad to help. :smiley: Hope to see some of your work posted. :slight_smile:
-K