# Question about simple deform modifier

Hi,

I am trying to teach myself modeling using Blender.

To do so, I am modeling a motorcycle tire. I am using the simple deform modifier.

I created the tire in a linear fashion, and then applied the simple deform modifier. This modifier uses a separate locator as its Axis, Origin. I had to rotate this axis origin so that the tire would actually bend around it in a realistic way. So far, all that seems to work as expected.

My question is: why does the tire not seem to use the axis origin as the center?

For example, here is the tire (the axis origin is highlighted):

See how the tire is properly rotated around 360 degrees, but it does not center around the axis origin. I need it to use that axis origin as, well, the axis. Does it have something to do with either the transforms of the tire or the transforms of the axis?

Here are their transforms:

The axis origin:

The tire:

My only guess is that it may have something to do with the fact that the tire is not currently scaled to 1.0. That said, it is scaled to .156 (roughly) but the first image would suggest that the scale is only about 2 times off.

Short version: I’m confused

Any and all help would be appreciated. Thanks!

there you go.

btw if you want i can make a quick video on how to make a tier, or do you feel like figuring urself?

Wow. That was fantastic and very informative. Also custom for me! I feel really special

I will have to watch it a few more times, but on first glance it makes a lot of sense. What you are saying is that the “length” of the object never changes, it merely bends around its own origin (assuming I have not done the deformation around different point or have moved the origin). In other words, it basically it has to do with the width of my original object. If I have a bar that is, say, 1 meter in length, and I do the deformation around its origin, then I should get a donut that has a radius at its center that is 1/(2pi), or .16 (using the formula that Circumference = 2pi*r).

So it seems to me that I should abandon the reference geometry, and just figure out what the math is and do the deformation around the object’s center then.

I’ll have to sit down and do a little math to figure out exactly what the length of my object should be for its given origin, but that shouldn’t be too hard.

With regard to your second post, I’m not exactly sure what a tier is. I tried googling it, but couldn’t find anything. So from that perspective, sure! I’d love an additional video. But seriously, don’t go out of your way any more if it is any trouble at all.

Thanks again!

i didnt understand all that math stuff, but just make the circumference of the tire equal to the length of what you are using the bend modifier on, and have the origin on the outside surface of the tire.

here is a tire, its not good, but it shows how to stack the modifiers.

Thanks so much. I’ll look at it when I get home.

The math basically just does exactly what you were suggesting. It figures out the circumference of the tire based on its diameter (19 inches in the case of the motorcycle I am modeling).

Feel free to ignore anything past this point. I’m just going to describe the math for anyone else who stumbles on this post.

The formula for determining the circumference of a circle based on its diameter is:

Pi x diameter

In my case, the diameter of the wheel is 19 inches. So the circumference would be:

3.14 x 19

Or:

59.66 inches (which Google tells me is 1.52 meters).

So now I just have to make sure that the length of my tire is 1.52 meters.

Thanks again for your explanation. It was by far the best explanation of the modifier I’ve seen yet.

Just downloaded this and it is very helpful. Thanks. The nice thing is that the basic way you constructed your tire matches the way I was approaching it so that makes me feel like I am on the right track. It also taught me about the bevel modifier which I had not yet played with, so double win.

Thanks again for taking the time to help me with this, I really appreciate it.