Unwrapping tyre treads
Hi all
I'm modelling a car and I've come to the point where I'm unwrapping it, though I'm not too experienced at it all. I'm unwrapping one of the tyres as a separate object and have got to the point where it's all done apart from the treads.
I'm using Modo, and as you can see in the screenshot I've highlighted the outer edges and cut it at 2 points across the width in the hope that Modo will separate those sections and lay out a nice flat tread UV for me, but it won't work. I originally tried it with 1 cut across the width so I wouldn't have two seams, but that didn't work so well either.
What you can't see in the image is that within the messy UV's on the left a lot of them are overlapping too. I can relax it but then the UV's get even more spread out and wonky looking, anyone know what I should be doing to unwrap this correctly?
Thanks
I'm modelling a car and I've come to the point where I'm unwrapping it, though I'm not too experienced at it all. I'm unwrapping one of the tyres as a separate object and have got to the point where it's all done apart from the treads.
I'm using Modo, and as you can see in the screenshot I've highlighted the outer edges and cut it at 2 points across the width in the hope that Modo will separate those sections and lay out a nice flat tread UV for me, but it won't work. I originally tried it with 1 cut across the width so I wouldn't have two seams, but that didn't work so well either.
What you can't see in the image is that within the messy UV's on the left a lot of them are overlapping too. I can relax it but then the UV's get even more spread out and wonky looking, anyone know what I should be doing to unwrap this correctly?
Thanks
Replies
Are you sure want to unwrap this high poly model?Don't you intend to bake a low-poly?Unwrapping that kind of detailed tire seems a bit pointless to me.
Anyway, thanks for the reply igi, I've been asked a few times if I intend to make a low poly and I've said no as this is just for modelling practice and not for a game or anything. Beginning to reconsider though if it's going to make unwrapping and texturing harder in the long run...
Am I missing something though, even if I bake normals off this high poly onto a low poly, do I not still need to unwrap the high poly first?
Also I'm highly suspect that you get hard surface modeling wrong..Do you use 'tab' key during your modeling process?Because I don't see any subdivision enabled.
Looks like I'm going to make a low poly version of the car and the tyres anyway, seems the best way to go
Also, is it correct to subdivide my mesh to an even higher level before baking the normals? Is there any issue with it becoming too high poly and creating a messy/bad normal map?
Iterations and
Render Iter
If you want to work with lower iterations for speed you can just use a higher render iteration amount to get a smoother bake.
If you subdivide too much, the rendering will take too long,most of the time there is almost no visual difference between 3 and higher subdivision levels
Iterations(viewport)
and (click to enable)Render Iterations - this is the one you set for your bake.
This allows you to set iterations to 1 or 0 for fast viewport response but set render iterations to 2.
[edit] Doh, too slow
And no, there is no reason to UV the high if you're baking.
I've got an issue though, the normal map comes out like this:
I've made sure the cage isn't too large, images of the low and high poly + cage are below:
Anyone know what I've done wrong? If you guys need to see any of my render options or anything let me know and I'll post images of them too
Now my issue is that the normal map is appearing totally blue. I have made sure the high poly is picked in the projection modifier...so not sure what the issue is. A friend has recommended I try the Xnormal tool so going to give that a go...
I didn't think getting some normal maps from a high to low poly would be this complicated
http://wiki.polycount.com/NormalMap#UV_Coordinates
Also, it looks like the treads in your highpoly model are perfectly vertical. If so, the sides won't be picked up in the bake. Make sure the sides of the treads are sloped instead of vertical cliffs.
Page 3 of this tut shows why.
http://wiki.polycount.com/3DTutorials/Modeling%20High-Low%20Poly%20Models%20for%20Next%20Gen%20Games
As for the UV's, these are the ones from my low poly mesh, doesn't seem to be any overlapping. The high poly mesh UV's aren't used, right?
One thing I've noticed is that I have some text in my high poly which doesn't exist in the low poly, so there are no Uvs for it, would this be an issue?
There's still the issue of those overlapping UV's though and where they are coming from, which I'm a bit stumped about if anyone can shed any light on that (if that is the actual issue)?
AKA MAGIC FIX, that sometimes works when you have errors for no reason.
1. Create any type of primitive, a Box for example.
2. Collapse the modifier stack into an Editable Poly.
3. In the Editable Poly, use the Attach button and choose your low-poly tyre model.
4. Select and delete the primitive element, the box for example.
Another way to do it is to export your low-poly tyre model to a format that cannot preserve the hidden corrupted data, for example OBJ, then re-import it from the OBJ file. This cleanses more thoroughly than the Attach method, but may lose some data, like multiple UV channels, or anything else not supported by the export format.
In either case, any modifiers on your original model will be lost. For example the Projection modifier. UVs are typically OK, since they're stored in the mesh itself.
Now, I'm no normal map expert, but it seems a bit off, like quite busy in places where it shouldn't be? Any tips on how to improve it?
I don't mind that the two circular shapes on the right (top two) are a bit wrong, they're hidden inside the tyre so that's probably why the normals are off. It's mainly the tyre treads on the left and the rim on the bottom right that I need to look good.
This, by the way was created from a turbosmoothed high poly version of the tyre which hopefully fixed some of those vertical edges
Thanks for your continued help so far guys!
I did manually edit the tyre tread UV's as when I applied the checker texture the checks on the side of the tyre were wider than the ones across the width, even though they were part of the same UV. I therefore re-spaced that whole UV section to try and get the checkers to be more the same size around the tyre, maybe I messed it up somewhere along the way
Should always aim towards getting as average checker size in both direction to be the just about the same, obviously its not completely possible because the inner and outer part will be different sizes, but try get some kind of compromise.
Well you wouldn't have to do that.
I'd suggest simply mirroring the tyre tread into quarters or halves. It does depend on what kind of specs you're working to. Chasing high texture resolution sometimes isn't worth it if it causes visible seams all over your model.
http://img859.imageshack.us/img859/8900/lowpolynormalsxnormalno.jpg
Looking at the two main elements on it (left hand side and bottom right) I can see some artifacts on the inside of the tyre rim, not sure if the tyre tread looks good or bad though? You guys will have to tell me that...
I rendered out the low poly with the normal map applied. It seems that the treads may be inverted and in general the normal map is a bit wavy. I assume the wavyness is because I didn't straighten out my UV's before baking? Which I can do easily if need be. How would I go about properly flipping these inverted treads though?
http://img217.imageshack.us/img217/2391/tyrenormal.jpg
Cheers!
the wavyness is because you're projecting a cylinder onto a series of planes. It's not possible to get rid of it altogether.
There's a whole thread about it:
http://www.polycount.com/forum/showthread.php?t=81154
http://img718.imageshack.us/img718/8900/lowpolynormalsxnormalno.jpg
http://img100.imageshack.us/img100/3751/treads.jpg
I have some more questions...
- There are obvious artifacts on the normal map and therefore on the mesh, would the next step therefore be to actually paint some of these out in Photoshop?
- How would I increase the apparent depth of the treads? They don't seem to stick out much at the moment, at least nowhere near as much as the high poly ones
Thanks!
Baking an AO in you case will also help selling that little more depth.
Also, don't paint over your normal map unless you know what you're doing.
Did you do something weird here like add in more segments to your low after you baked your normals? You shouldn't be getting noticeable waviness on an object with that many sides.
Waviness etc: http://www.polycount.com/forum/showthread.php?t=81154
Care to upload objs of the low and high? Something doesn't really seem quite right, you shouldn't get that sort of waviness with the amount of geometry you have there.
Also it looks like you might have your normal map loaded as a bump map or something, the shading doesn't seem quite right. Make sure the material type is "normal bump" and that you're not loading a normal map directly into the bump slot.
Now go to 3dsmax and open the Material Editor (M). Select a new slot and go to the Bump slot. First set the amount to 100 (the default is 30). Click on the None button and from the window that apperars select Normal Bump. Click the Normal slot and from the window that appears select Bitmap. Load the .psd file you just saved. There is one more thing you need to do to see the normal map in the viewport. In the Material Editor check the DX Display of Standard Material in the DirectX Manager section.
So i'll try that tonight
I'l also try to send you the OBJ files after work later or upload them here, cheers
Of course, if I do have any more related questions, I'll post again
Also how you're doing the rim is rather strange, that should be welded and flow into the tire.
You should be baking with the entire lowpoly model there too, not deleting the mirror section. Just offset the UVS exactly 1 unit off the grid(will still work and you don't need to move them back). Otherwise you will get seams there when you copy in the other section.
I would still be happy/curious to take a whack at the low here, I think there are a lot of little things that you can really improve upon still, and if you keep doing them the same way in other models you're going to run into problems/unneeded headaches.
A couple notes: by simply starting with an appropriate amount of sides to the cylinder you shouldn't have any noticeable waviness. I think the waviness problem you had was from adding extra geometry, but not round geometry, to your mesh. I used 24 sides here which seems to do a great job, but you could bump it up to 32 if you really needed to view the tires up close, and still be way below the triangle count of your previous version.
24 or 32 are good numbers, because when you do LODS 24 becomes 12, then 6. 32 becomes 16 then 8. I always try to stick to easily divisible #s for cylinders.
I merged everything into one seamless mesh, you had two bits intersecting here wasting a lot of tris on things that wouldn't be seen, and creating extra uv seams/bake issues where the two objects intersect. You also had a random little detail modeled into the lowpoly(not sure what its called) along the edge of the rim which I removed, the normal map can represent this just fine.
I unwrapped the main chunk of the tire that would face the player onto on seamless island, this helps while texturing and helps UV distortion as well. I offset the mirror section which in this case is simply the treads by exactly 1 UV unit, this helps the object bake correctly as mention previously. Getting even UV detail is really important for consistency as well.
Low OBJ: http://dl.dropbox.com/u/499159/tyre_low.obj
This was baked in Maya but should look more or less the same in Max. You may need to add a little more geometry to the inner rim details to avoid smoothing errors in max.
I didn't realise i would be able to remove that metal clip from the tyre rim, I assumed that any geometry like this would have to represented in the low poly in a basic form, good to know!
No I do not mind at all, infarct I think its probably a good idea to look at them closely side by side to take in the differences.
With the little detail there, that sort of stuff is really what normal maps do best. Represent small shapes and details where there isn't much/any silhouette change. What you really need to model in is your larger forms, shapes, curves etc that affect the silhouette, because a normal map can't fake that.