I can not import new UV's due to flipped normals??? (XSI)

[system]

I have a ZTool I have been working on, and I had to do some retopology as it is intended as a game mesh.

So I finished the retop, and then it was time to export it for some UV’s. Bringing it on in to XSI, the normals were inverted so I had to flip them.

Now it’s time to import it back in to ZBrush, and every time I do it, the model “explodes”. I did NOT change the mesh at all, but the simple fact that I had to flip the normals makes this happen. To test it, I took the original ZTool and flipped the normals of the lowest subdiv, and re-importing it makes the same thing happen.

So I tried flipping the normals in the mesh with the new UV’s before importing it in to ZBrush - and ZBrush errors.

I tried to make a displacement map in XSI, but Ultimapper errors. So there is no way to get the displacement map exported on the new UV’s that I know of.

And projection with subtools is giving me very sub-par results…

I’m not sure what to do at this point… but I feel very discouraged like I just lost alot of work…

[system]

I would just like to add… While you edited the thread name to list XSI - this is a ZBrush problem.

To confirm it, I went to subdiv level 1, deleted all higher levels, flipped the normals, and exported the OBJ. Then I took that one and imported it as the subdivision level 1 - and when I step up subdivisions it “explodes” in the same exact way.

So this confirms that it is ZBrush that does not play well with “flipped normals”. But this is a huge problem because it is exporting flipped normals!

Problem is, if I import in to another application (I’ve tried XSI and Modo) I have to flip the normals to work with UV’s properly - but if I import it back in to ZBrush like this it explodes - if I try to flip it AFTER doing the UV’s ZBrush will error on import.

So in conclusion, when I am using retopology in ZBrush I of course have to do the UV’s… but I have no method of being able to do this because ZBrush exports them flipped but can not import them flipped, and explodes if I flip them over in another applicatiion (which is neccessary to work with the UV’s).

[goast666]

If you are encountering this error it is an easy fix. I myself use XSI, anyway. Instead of projecting the mesh within the retopo process, you can simply create an adaptive skin for the first subD of the retopo. Append that as a tool and project that onto the mesh. Before you project, or after, flip the normals (sometimes retopo makes them flipped…no idea why). Once the normals are correct, export them out and map them in XSI. Then import the correct normals with the unwrap, and project that onto the previous mesh that has the high poly detail. If this doesn’t make sense shoot me an IM and I can walk you through my process step by step.

Good luck.

[system]

If you are encountering this error it is an easy fix. I myself use XSI, anyway. Instead of projecting the mesh within the retopo process, you can simply create an adaptive skin for the first subD of the retopo. Append that as a tool and project that onto the mesh. Before you project, or after, flip the normals (sometimes retopo makes them flipped…no idea why). Once the normals are correct, export them out and map them in XSI. Then import the correct normals with the unwrap, and project that onto the previous mesh that has the high poly detail. If this doesn’t make sense shoot me an IM and I can walk you through my process step by step.

Good luck.

Thanks for the response. I was pretty much just sitting around not able to work because I didnt know what to do with this problem lol.

Just reading that it does not make sense, but I have to attempt it first because things typically make more sense when you try them compared to in text =D

I’ll let you know if I have any problems!

[system]

Did you ever get this to work out for you?

This is a problem I have had quite often.

One of my work arounds has been to use Headus UV Unwrap. If you use Headus to unwrap your retoped mesh, then import, you won’t get an explosion.

For me the big issue really is when you need to retain the original UV’s in the first place. I would really like for a retoped mesh to retain the original uv’s, but I’m pretty sure that’s impossible. It would be really nice for instances where you need to have your UV’s laid out and it has been passed down the pipeline. I realize it’s impossible in the sense of retaining the actual UV’s. But what would be amazing would be if they were projected somehow onto the new mesh.’’

Currently I have a project where I need to keep the UV’s in an exact spot. So I retop, unwrap in Headus UVUnwrap, then bring it back into Maya where the rest of my mesh is laid out, then I possition my new UV’s into place. I will then export the mesh from maya, then import it into ZB, and BANG! Explosion! Haven’t found a fix yet other than just exporting from Headus.

Anyways, I’m going to try this. I didn’t actually realize it was because ZB is flipping the UV. I’ll play around with it and see what I get.

[system]

I did find a fix for it - I took notes incase the problem happened again and I do the check for inverted meshes every time I use retopology. Here are the steps.

1. Create adaptive mesh for 1st subdivision.
2. Flip the normals in ZBrush to be correct & test in XSI (or any other external program) to make sure they are proper.
3. Load both original high-quality mesh & the new adaptive mesh in ZBrush
4. Flip the High-Quality, and then Select a Zsphere
5. Rigging > Select High-Res version
6. Topology > Select low resolution
7. Hit Edit Topology
8. Turn on projection and make a new adaptive mesh.

After these steps your ZBrush tool should be “fixed” since it is right-side-out. You should then be able to use the traditional ways of transferring UV’s without problems.

Hope this helps!