# What would be the best way of simulating a flat tire?

I’m going to be in need of giving a car a flat tire for an animation. The camera will be pretty close up on the tire and it needs to actually see it as it deflates.

Each wheel of the car is a seperate object. The car will be driving very slow… almost ready to stop when it runs over a sharp object to cause the flat.

Just curious to see what you think might be the best method to accomplish this?

I was thinking possible animating shape keys … maybe a lattice (although I’ve never used a lattice)

Thanks Atom… I’ll take a look at the link. It would only be rolling a few feet as it is becoming flat, but if needed, I could have it come to a stop before deflating.

I was just messing around with shape keys… but imagine a tire with a rim…

I was able to get an approx. shape with shape keys by using proportiional ediitng… but I need to find a way of keeping the edge of the inside of the tire that is mounted to the rim not to deform as I am forming the flat look.

Is there any way to prevent certain edges or vertices from deforming when using shape keys and proportional editing?

Curently I am selecting a few single vertices at the very bottom and pushing upwards in z while tweeking proportional editing. It would be helpful to know for the future, even if using lattice is a better option. … I’ll check that link now.

Personally I think a lattice would be easier. I’d have to try it to get the exact steps involved, but it should allow you to move the lattice along with the vehicle and only the portion of the tire that meets the road would pass within the lattice and be deformed by it. You’d add hooks to the lattice and animate them. This would allow you to change the shape of the lattice and squish the tire over a period of time.

That would be great Storrboy, anything you find out, I would be very interested in seeing whatever you come up with… I just tried Richards approach with the Laspien smooth modifier… While it works in giving somewhat a deflated look and is animatable, but to do it, I had to create vertex groups, but as the car is moving of course the deflation is not occuring where the tire meets the road. Its entirely based on where the vertex groups are at any given point in the rotation.

I’ve been trying to find a reference video… because I have these tires parented to an empty… drivers are used to make the wheels turn automatically as the vehicle moves forward and backwards, On my first test(stationary, not moving) , as the tire deflated I moved the tire and rim downward in Z to keep it touching the ground. What I’m not sure about is how things happen in real life…

Does the whole vehicle kind of dip based on the flat…But if I rotate the parent(the main car empty)… the opposite wheels are going to raise off the ground.

If for an animation, you can cheat the camera since it won’t see the opposite wheels, only the side you are getting the flat on.

I’m going to play around with it tonight, but I confess that in a quick test, it’s not behaving the way I remember it. The lattice seems to influence the whole tire and not just the part that is inside it.

Can’t you make a vert group to be affected by the modifier?

I think I realized why it wasn’t working. The lattice has to encompass the whole object - I was trying to work just in one area of the object and it affected the whole. I put up a blend with a very simple setup. If the link doesn’t work I’ll attach a different way.

This can be extended with additional constraints like Floor (but it may take me a bit to figure out how) so that the lattice or the wheel can’t penetrate the road. As well as rigging the car so the wheel moves apart from the car etc. But this should allow you to animate the flattening process. In this test I parented the tire to the rim, the rim to the car and the lattice to the car - but in hindsight should have parented to the rim for additional rigging. The tire gets the lattice deform and I used two shape keys on the lattice. The base key is fully inflated and a deflated one. This would allow keying them to get flattening over time. Rotate the rim around the Y axis to see working.

One problem I now see with this method is that a tire going flat at moderate to high speed would wobble and deform all over. I think you’d need either a very complex lattice, or maybe a softbody would be better? But if you’re slow moving ( and you stated you were ) or mostly stationary it might work well enough. At least as a starting point anyway. More rigging and keying would certainly help.

Like I said, this is a simple setup, but hopefully it helps.

I really appreciate you taking the time to put this together Storrboy. I’ve never used lattices so I do have a couple quick questions. But first let me say the vehicle is going to be very slowly rolling up to the front of a hotel entrance. Only driving a couple miles per hour for a about a second or two. Right before he comes to a stop he is going to roll over something that puntures the tire. If worse comes to worse, I’ll animate the deflate after he comes to a stop. But a couple questions on the lattice because I need to recreate this for my scene.

1. So you first create the lattice and encompass the entire tire

2. What I couldnt tell is how you parented the lattice… it doesnt seem like it is done in the modifier, so I am guessing the standard way… select lattice … than select parent… than ctrl P. One thing that threw me off a little was your comment about should have parented to the rim… if you did that, wouldn’t the lattice then rotate since it is the child of the rim and that would be turning?

3. What I need to look into is how you actually deformed the latice…and create the shapes… but I can look that somewhere.
maybe you just go into edit mode with latice and start pushing verts to form the shape. The other thing is rim or the inner tire(where the rim meets the tire… did not deform, which was a problem I was having on earlier tests.

4. But what I like about your method, is despite me rotating the tire, the flattning stuff stays at the bottom where it should.

Again, thanks for taking the time, please feel free to add anything else you discover. I’m just starting to animate for a big WIP project, click the onearm bandit and casino link in my signature if you want to take a look.

@craig For certain modifiers, it seems that would definitely be the best way Craig… what I’m not sure is if you create a vertex group and then use proportional editing… if you have your area set kind of large will it overlap into the non vertex group vertices or will it limit itself to just those verts in the group…

No problem. And in reality, a slow moving, punctured tire would take a couple of seconds before it deflated to a visible level anyway, so if you wanted to wait until it stopped you could. They don’t really blow apart unless it moving rapidly or massively over pressurized.

1. So you first create the lattice and encompass the entire tire

Yes, scale the lattice to the desired size while in object mode, if you do it in edit mode, it will take the new shape as a transformation.

1. What I couldnt tell is how you parented the lattice… it doesnt seem like it is done in the modifier, so I am guessing the standard way… select lattice … than select parent… than ctrl P. One thing that threw me off a little was your comment about should have parented to the rim… if you did that, wouldn’t the lattice then rotate since it is the child of the rim and that would be turning?

I just used the control-p method to parent to the car. This way the lattice moves with the car but does not modify it. Yes you’re right about parenting to the rim, I hadn’t thought that far. In a real setup I might instead use a bone for an axle or strut then parent the lattice to that. The idea was to have the lattice move with the rim, which doesn’t deform but moves up and down and pivots on the steer wheels).

1. What I need to look into is how you actually deformed the latice…and create the shapes… but I can look that somewhere.
maybe you just go into edit mode with latice and start pushing verts to form the shape. The other thing is rim or the inner tire(where the rim meets the tire… did not deform, which was a problem I was having on earlier tests.

That’s exactly what to do. It’s just like doing shape keys on a mesh.

• Create the base key > edit mode > do nothing > object mode to finalize
• Create FlatTire key > edit mode > move verts to get desired look > object mode to finalize.
• Continue for any other shapes.

Since only the tire has the lattice modifier, it’s the only thing affected. Just make sure to add enough U/V/W division to the lattice so that you can better control where the deform starts and stops. (The sliders for this in the lattice data panel - similar to mesh data)

1. But what I like about your method, is despite me rotating the tire, the flattning stuff stays at the bottom where it should.

Again, thanks for taking the time, please feel free to add anything else you discover. I’m just starting to animate for a big WIP project, click the onearm bandit and casino link in my signature if you want to take a look.

No problem! Call back if you need any other assistance.

I meant that the vertex group could control the area of influence in the lattice modifier.

How would that work when the tire rotates? Wouldn’t that group move out of the flattening area?
Or maybe I don’t understand what you mean?

Make a group of the entire exterior of the tire, so as it rotates inside the lattice it is affected by x percent of influence. This way, you don’t deform the inner rings that would be mounted to the rim. I will try to find some time to make a working example I guess, to prove to myself that I understand as well.

Here is a simple torus with two vert groups and a default size lattice with some deform. If you rotate the torus, you will see the flat side is always on the bottom

Not as detailed as your project, but maybe this can still help.

### Attachments

tire_flatten.blend (682 KB)

But incomplete, so there is a lot to be done for application and animation, like parenting and such

Thanks for posting it Craig… I just got back, I’m going to take a look at tomorrow with fresh eyes… thanks again

I tried this way, see if you can be this way Teste pneu furado1.blend (617 KB)

Edit I did not get it up fast enough i see there is a fine example here now but It may help with some ideas anyway
Here is my old blend with the lattice.
http://www.pasteall.org/blend/24887
Demo here there is a different model in the beginning then the one with the wheels.
https://vimeo.com/34789791

The Cast modifier in the Cuboid projection mode with the From Radius option enabled seemed to be promising at first. But now i’ve been trying to bruteforce the math formula to drive the values in a way that the bottom of the tire won’t go thru the ground and will still show the right amount of bulging for hours :spin: