# Animating a car

Hi,

I’m planning to animate a car. For that, I’ve done some tests to figure out how to procede, but I’ve got some questions.

My first question is about animating the suspension in the wheels. The wheels need to follow x and y motion of the main control empty (that empty has everthing parented to it), but must follow the road exactly (every bump and so forth). Obviously, the body of the car shouldn’t react to every bump. I’m planning to let the car move along a curve as a path. It would be most convenient if I could add a second curve, which matches the surface of the road exactly, which is then used to determine the z position of the wheel control empties, kind of like having the wheels run on rails. But, there is no constraint like “copy z location of path”. I can’t use a normal follow-path, because when I put the bumps in it, the path gets a different length, and control empties for the wheels start lagging behind or overtake the car’s control empty.

It’s kind of difficult to explain. In short: can I let the wheels move along with the main control empty, but let their z position be determined by something else that exactly matches the surface of the road (meaning, so manual fiddling with keys and IPOs)?

My second question is about the rotation of the wheels. At the moment, I have animated a constant forward motion of the car, and constant rotation of the wheels, which I slow down or speed up with a time IPO. The problem with this is, that the wheels already have an IPO-block attached to them for the rotation, so I can’t assign the IPO-block containing the time IPO. I have to copy-paste it everytime I modify it.

Is there a better way to control wheel rotation, so that it perfectly matches forward motion?

I think It’d be possible if the wheels and the body of the car were seperate objects. That way you can make the wheels bump a lot and the body of the car too, but less. They just have to stay together, which shouldn’t be a problem. Just my humble opinion, though.

The wheels are seperate objects. The problem lies in controling the motion of the wheels. I could manually manipulate IPO’s of the wheels (or their control empties), but that would give a poor result. And having the control empties follow a seperate path is also not possible, because of the problems I described. At least, I don’t see how.

You could try using my Clamp To Constraint on the wheels.

Basically, the setup you’d be going for with this is to have all the wheels parented to whatever controls the position of the rest of the car.
Then, you’d create two identical curves that determine where the places where the centers of the wheels can go.
You would then give each wheel a Clamp To Constraint that points to either of these two curves.

Aligorith

Is your patch going to be part of Blender? Maintaining custom builds of software is rather cumbersome.

That constraint does seem to be what I need. One question though: Can you clamp to only one axis (z), because I don’t want my wheels to move sideways when the curve makes a wobble?

I would do it a bit differently though. I would put an empty between the wheels to which I add a clamp to contraint, and then add a copy z location to the wheels, to copy the location of that empty. That way, you can have one curve for the wheel position. This would do for me, because I’m not animating a monster truck, whichs would need indepedant suspension on each wheel when driving over large objects.

But, when this contraint is not available, what would be a good alternative?

Hi,

maybe the stride bone and stride path is the right solution. Sorry I do not know the details how to set it up but maybe this link will help http://de.wikibooks.org/wiki/Blender_Dokumentation:_Stride_Path

Jiri

I’m not really into armatures, but from what I can gather, this is not what I’m looking for. But, I will investigate some more.

When I get home I will post a car that the great Sketchy set up. Its an all in 1 rig for animating cars. Also Roubal posted a cool method, If I can find them I will post them for you.

Thanks, I look forward to it. A search for Roubals work doesn’t yield anything (for me at least…)

BTW, if I don’t respond (within two days or so), could you send me an e-mail? I’m having problems with e-mail notifications of this forum. Very annoying.

Sorry, I had to work late and by the time I got home it was 9pm. I went straight to bed. I SHOULD get off earlier today. 12 hour workdays suck.

This does not solve my suspension problem (you still have to animate it manually, instead of letting it follow something), but the armature setup it uses could be of interest. I use a bunch of control empties now.

I first have to figure out if it gives advantages, though. I have never worked with armatures, actions or the NLA, so I don’t know if it will actually be an advantage.