Hi. If you haven't already, take a look at this list and see if it applies to your problem.
Normal Map Troubleshooting
I can't be certain, but you might want to double check your model via xView for things like Flipped UVW Faces, Overlapped UVW Faces, and Face Orientation since they're common causes of Normal Map artifacts.
xView
It's hard to tell unless I take a look at the object. Is it possible for you to detach just the problematic portion of the model and upload it? File must be zipped for the forum. If you can't upload it for proprietary reasons, I understand. If you can't upload, then maybe you can upload a screengrab showing both UV selection in UV Editor window and the Perspective View.
Hi. Sorry for the late reply. I've not checkd the forum over the weekend.
I took a look at your file, and the bulk of the problem was due to your model having lots of N-gons - polys with more than 4 sides. One way to fix them is to basically revealing all hidden edges, but you will end up with topology that is not desirable for subdividing. I edited your model partially to show how you could go about fixing it. I removed the problematic edges and used your exisitng vertices and polys to reconnect/cut new edges. I did not create additional polys. The only thing I edited via Unwrap UVW was to flip the side portion of the dial (?) object. The rest was done in Editable Poly.
See attached files.
Your model still has problems as far as topology is concerned because subdividing doesn't create smooth curves where they should. But, one thing at a time.
Hope this helps.
Yes, tri's are n-gons. All meshes, in fact, are made up of triangles. For the purpose of subdivision modeling, you want to keep visible triangles minimum. They're perfectly fine for low-res, and even for subdivision. My point was to not use polys with more than 4 sides with hidden interior edges. You could end up with pinched, warped, or overlapping polys. They produce artifacts in your subdivision for the high-res.
If you are building this as a game asset, ideally, you should have two low-res versions. First low-res would be built out of quads with good edge flows so that it produces nice, high-res subdivided mesh when turbosmoothed. The second low-res version would be the optimized version of the first one. This is when you reduce your poly count, but it should not have n-gons with more than 4 sides. And it could be made up entirely out of visible triangles. You would then use this optimized version and apply normal map that was extracted from the first version.
Sounds like you're in the process of learning to model. Good luck and enjoy.
@Anonymous wrote:
I cant open your file, for it was saved in a newer version; but, I did try your suggestion, and it doesn't solve the problem. Even if I detach the faces and mirror them, in the viewport, with xview>flipped uvw faces enabled, the faces are still highlighted in green.
The part I flipped was just the side portion of the dial. I flipped the UV's in UV Editor Window, not the mesh in Viewport. I have re-attached the partially edited file shown in my pic. I saved it as 2012 this time.
A lot of the times, flipped UVs are caused by how the mesh was created during modeling. As I have already mentioned, avoid those polys with more than 4 sides with invisible, interior edges. If you need to keep them as they are, cut the edges so they become visible and end up with quads and/or tris. Otherwise, overlapping UVs can also occur. Mirroring meshes can also create flipped UVs. In most cases, they can be fixed by flipping the UVs in Edit UV Window. In the case of your dial object, I am not sure how they ended up flipped.
Hi. Sorry about the belated reply.
Those problems you describe occur because of the way your model was built - polys with more than 4 sides. Those often result in overlapping, internal polys. When that happens, your UV's will end up overlapping/flipping as well. Most people who use these types of meshes don't even realize it, but they are there nontheless. You can often fix them by changing the way your polys are constructed by redirecting your edges in the mesh itself, but you may still have to edit the UV's. When you have a poly with more than 4 sides with invisible interior edges, they are still made up of triangles even if you don't see them. 3ds Max has to know how you want to divide them into triangles, but if you don't specify, you end up with whatever it thinks is the most efficient way. Then, you will likely find overlapping triangles which will result in overlapping/flipping UV's.
You may need to spend a lot of time fixing both your polys and UV's. My advice for you in the future is to build your mesh in such a way so that you don't have these hidden triangles before you start unwrapping UV's, not after. You will be re-doing a lot of unnecessary steps.
You may remember my pic from earlier showing a bunch of notes. I'm attaching a simplied example below to explain the problem you're having.
xView showing overlapping UV's in green:
Btw, you're not annoying me. 🙂
In your case, what I noticed was that you had a lot of polys with more than 4 sides. I was able to fix a bunch of them just by re-connecting the Edges using either Cut or Connect and turn them into quads. Some cases, I removed your existing internal edges with Remove tool without removing the verts.
So, few things to remember for future modeling for your low res model:
-keep them as quads as much as possible.
-Triangles are better than Ngons with greater than 4 sides.
-If you have polys that are neither quads nor tris and don't want to re-do it, then cut (connect edges) them into quads and tris.
-Don't use the mirror tool. If you do, remember to Reset Xform and flip the normals of the mirrored part. Otherwise, you end up with what is also called "negative scaling."
-If you need to mirror parts, then use the Mirror modifier or Symmetry. This will not affect your normals.
If you want to save time unwrapping UV's by mirroring, there are certain things you can do. This is assuming you have perfect symmetry of the model:
-Model just the half with Symmetry modifier. (Remember, clean mesh) Symmetry will help you see the whole model. And it does not flip your normals. Or, you can model just half without the modifier. Either ways is fine because you will delete the symmetrical part once your half is done.
-Unwrap the UV's of the model (original half). Collapse to Editable Poly when finished.
- Apply Mirror modifier or Symmetry, but don't weld or slice at the the seam. Collapse to Editable Poly.
-Apply Unwrap UVW.
-Go to sub-obj Poly UV mode and make sure Select by Element is checked. Select the mirrored part of the mesh in viewport.
-Open UV Editor window. You should have your half selected that is perfectly overlapped.
-In Tools menu in Edit UV window, choose Flip Horizontally or vertically depending on how you mirrored your mesh.
-Use the Move Horizontal/Vertical tool and move your whole island so that it meet the other half at the seam.
-At this point, you can't weld the UV seam because your model isn't welded at the seam. Get out of sub-obj mode.
-Apply Editable Poly and weld the vertices at the seam.
-Apply Unwrap UVW again and weld the UV vertices at the seam.
-Collapse to Editable Poly.
I sometimes do what I just described on just parts of the model if it has symmetry. No need to Unwrap the whole model if you can do it on just the half. Try doing this on simpler models. The more you do it, the more you will get the hang of it.
@Anonymous you for the kind message @Anonymous. I’m sorry to not have been as active as I would have liked in the forum in recent months. Your message reminded me of how much I enjoyed being part of the community. I have been a part of this community for a very long time, and I have learned so much from everyone, and often, in the process of helping others. I hope the newer members will do the same, by helping others.
Cheers!
@Anonymous wrote:
@ekahennequetI just want to thank you for all the detailed information and fine examples you have provided in this discussion. Even after 3 years have passed on this thread, you not only helped me in understanding more on how UVW mapping works, but also let me in solve an issue I've been pulling my hair over for the last day and a half!!
I was struggling with a horrible distortion in a baked normal map as I highlighted below. And what was very weird is that the other side was perfectly fine, even though they were all on the same UV island layout.
When you mentioned that sometimes the problem is in the mesh itself, and having to re-align the edges, I thought "well, I've tried everything. It wouldn't hurt." So I flipped the edges, my jaw dropped, and I was smiling and jumping like a monkey seeing his first banana in weeks! Suddenly it was all working like magic. Here it is.
I'm writing this first to thank you for taking the time in explaining in detail and sharing your knowledge, and second to leave my issue and resolution as a reference for those who might need it in the future. My sort of way of paying it forward 🙂