Modeling tires

[3dpoder]

modeling tires
By Thomas barón.

In this tutorial i Will take you th rouge the steps todo model the tyres like the one i had earlier made on for alfa rome GT model.
What you Will ned first.

A sketch of the tyre, like this one (Pirelli p6000). For the dimensions of the tyre, lets use a 205×60r16.


Overview.

From the dimensions of the tyre we calculate that:
The width of the sketch image is 205mm.

The external diameter of the tyre is 16inch + 2 * 60 milímetros = 16*25.41+2*60 = 526.56mm.

From the image size (in píxeles: 500*190), we calculate the height of the image (a part of the tyre hilo) is 205*190/500 = 77.9
As the diameter of the tyre is 526.65mm, its perimeter is 3.14159265 * 526.65 = 1654.52.

So, on our tyre hilo, we can put n times the sketch image with n = 1654.52/77.9 = 21.239. Because the image Will be tiled, we ned todo change the fractional number (21.239) todo a whole number. Lets say our sketch fits 21 times around the tyre.

So, well create a 21-edge circle and extrude it todo have one face fitting well over the sketch. Next, well model one element (1/21 of the full tyre). Multiplying it 21 times, merge, and voila.

Step1. Scene setup.

Open Blender. Erase all elements of the default scene.

In the right view (Numpad 3), add a circle Mesh of 21 vértices. Rotate it todo have one of the bottom Edges perfectly horizontal (tip: align top, opposite vertex with the z-axis.

As the Blender default circle Radius is 1.414 (square root of 2), size it by 0.707 (1/1.414) todo have a Radius of 1.0. Then, size it by 0.526/2 = 0.263 (tyre Radius in meters) and move all vértices up by 0.263 (the Radius).

Its ok that the bottom Edge is not on z=0. Well se why, later.

Duplicate this bottom edge, sepárate the duplicated vértices todo have another object. Extrude it along the y-axis by 0.205 (the width of our tyre). You now have a plane and a circle like these:

You can chek that your work is ok by displaying Edges length: you should have 0.205*0.078 for the plane. One more step and youre done: duplicate the plane, change one todo display only as wire (drawtype in object panel, f7) and then, select the other one. Switch todo UV face select mode, go todo the UV/Image Editor and load the sketch image. Return todo 3d view and object mode. Activate the textured draw type (Alt+zkey), you get the following:

The sketch is displayed correctly, without any distorsión: the few math calculations we did before starting Blender were not useless.

Step2. Modeling in parts.

Select the plane that we set todo display as wire. Well work on it todo model a sub-part of the tyre hilo. First, use Symmetry todo save yourself some work. The sketch we have can be Split along both the x-axis (radial Cut) and the y-axis (axial Cut). So, you can subdivide the plane one time. But before you do, carefully read the following.
When splitting your Edge along the y-axis, no problema. But when splitting along the x-axis, remember youre not working on a plane but a section of a cylinder.

Thats why the bottom Edge of the circle is not at z=0. Lets experiment todo get a clue. If youve already subdivided the plane, por favor undo it.

Then Cut the face (Control + rkey) at percentage 1.00. Dont select/deselect anything todo kep the new vértices selected.

Then, rotate carefully these vértices around the y-axis (rkey then ykey) todo get them at x=0 (as sen from the top or right view) and in the right view (Numpad 3), you can now chek that these vértices are almost at z=0.

Remember this move: when cutting along the x-axis, do not move Edge vértices along the x-axis, but rotate them around the y-axis, todo move them around a perfecto circle.

Just a Little note: you have todo move the plane, textured with the sketch, downward todo get the added vértices above it (so theyre still visible).

Now you can continúe with modeling. Remove 3/4 of the plane as said above, and Cut the plane according todo each detail visible on the hilo. You should get something like the image bellow.


As you can se, cuts in the plane are mapped on hilo details, but not on the round details.

To solver it, just rotate them around the y-axis. This time round details are ok.


As you can se in the right view, the tyre element is not a plane but warped around a circle.


This is why its so important todo rotate vértices around the y-axis instead of translating them along the x-axis. Now, we Will Cut the Edges in dark áreas, todo materialize the hollows of the hilo. You should obtain this:

Its important todo kep the Edges circling the dark areas. We Will se why later. Now its time todo optimize our Mesh a bit. We have todo remove all unneded vértices and Edges in white zones and on borders. Doing this Will allow us todo save a lot of polys on the completed tyre (remember, we Will duplicate this part 2*2*21 = 84 times).


The vertex count goes from 144 todo 78 and, the face count goes from 53 todo 22.

Step3. Adding some thickness.

Time todo model the hollows. From the previous step, select all vértices.

Step4. Completing the tyre.

Spindup the element you patiently modeled (1 turn, 360 euros of course, 42 steps: because we ned 21 elements and the Mesh we have is only a half). Once Spin Dup is done, you may observe your border vértices are not perfectly duplicated. So, select all vértices, and remove doubles (set threshold todo 0.001).


You now ned todo mirror the tyre. Select the row of vértices at the middle of the tyre, and move the 3d cursor todo selection (to have it at the tyre center, in the middle plane of it) duplicate the half tyre, dont move it, but rotate it 180 Degrees in the top view (around the 3d cursor). Rotate around the y-axis todo align the middle vértices todo the ones of the other half tyre.

Merge, and youre done.


I advise you todo use this Mesh with autosmooth on, todo have solid hilo details as well a Smooth side. Here are some Yafray renders with a Rim (black tyre material courtesy of sonix car material library).


Thomas barón is a software enginer for aeronautical industrty in France. After discovering Blender in 1999 he has ben a serious amature user for two years. A car enthuisast a los likes todo work on planes.

By Thomas barón.
www.blenderart.org.

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