Things got a bit tricky when we found out that the new "Up Armor HMMWV" required specific tires due to it's overwhelming weight. Normally, tires are tricky in their own right when it comes to 3d, but this type of tire especially posed a problem.....Asymmetry...
Most commercial tires have a repeating pattern that 3d modelers just love. A little bit of modeling, some array duplicates and BAM!!! A TIRE! No, none of that simplicity here...
So I did some thinking; how can I easily determine the pattern, replicate it and still have viable geometry and UV's? I was instantly reminded of a tutorial from several years ago in "Deconstructing the Elements." The guy essentially builds a volcano with a flat plane and a bend modifier and a bit of geometry based displace. In my mind, I thought "lets do the same, only in reverse."
1. As you can see, I started off with the cap of a cylinder (9 divisions & a Turbosmooth) mapped with a planar UV and the reference image.
2. Once the image was aligned on the cylinder cap, I broke all of the edges and rotated each element until they matched horizontally. Using the snaps, I pulled each piece to the previous vertex, aligned them together and welded the upper vertices. (notice the extra polys on each end are duplicates for a seamless edge tile)
3. Once the upper pieces were welded, I welded the lower but then removed the excess polys below the tire line of the texture. I trimmed up the verts on the top and bottom to align perfectly horizontal and then moved onto step 4 using the latest geometry as reference from here on in.
4. Now that the geometry was clean, flat and even I moved onto introducing the vertical cuts that would represent the sidewall ridges. Using "slice plane" I added a subdivision based on each vertical ridge, removed the initial lines and their verts, then chamfered those edges to represent the width of the ridges.
5. In this step, I began pulling down on the ridges to represent the varying height of each ridge. I also extruded the ridges on the side and began wrapping them around to the top (road side) of the tire.
6. Since the sidewall of the tire has a bit of a bow in it, I added horizontal connections and the road side ridges that occur between the sidewall ridges on the tread.
7. This is where it all came together. Starting off with an FFD modifier, I added the bow into the sidewall, rounded out the edge a bit and then added a bend modifier set to 360. A little vertical stretching here and there and it matched my original reference just fine.
8. Added the wheel hub, bolts, lug nuts and horizontal stabilizer(?) to finish it out.
9. To make it feel a lot more alive as seen in the top image, I painted the entire piece in Zbrush. A little bit of dirt goes a long way when it comes to any model. You'll notice how out of place the clean wheel hub is compared to the tire itself.
I love problem solving and this was a great example of it.
Hope you enjoyed.
