I’m trying to apply rigid body physics to a car model. I’ve tried to make each individual part of the car an Active Rigid Body object. After that, I tried to parent the car to a plane just below the car and add rigid body physics to that. It worked for a while, but then it started acting strangely, doing things like falling through the floor and randomly flipping over. Right now, I think that my best bet would be to group the whole car and make that group a rigid body object. Is it possible to do this? If not, what else might I be able to do?
In adding them all as a group is very easy actually. Select your group, find the Physics panel in the 3D Viewport, marked Rigid Body Tools, and press the Add Active button there. Change your settings appropriately for the selected object that you would like to apply to the group, and then in the Rigid Body Tools just below the Add Active, in the Object section select Copy from Active.
What do you have your active elements Rigid Body Collisions set to? You more than likely have the mesh Shape set to Convex Hull and have the Collision Margin set too high. If your are looking for a more accurate simulation you need to set the Shape to Mesh and the Source to Final. There are other factors that could be causing the ‘explosion,’ can you post a .blend??
Ok First off, I don’t know what effect you’re trying to achieve here. If you are looking for a realistic fall and “bounce” from the suspension, well, you’ve got a lot of work left to do here. The reason the car “explodes” with the physics on, as you say, is that the model is not set up for physics “as is” - meaning you have some object parenting and planning to do. Also object scale plays a part in the calculations, you have to apply all transforms on objects before or you’re going to get the results you described. Second, parenting the car to the plane as you did in the scene here is not going to give you any kind of favorable effect as far as the physics of the actual car model is concerned, it simply isn’t calculated with the setup you have.
Quick and dirty solution: combine the tires into one object, parent everything to the tires, set the tires (and tires only) Type to Active, Shape to Mesh, Source to Final, then go to the Scene panel, clear your cache and set the Steps Per Second well above 100 and the Solver Iterations to 30, you’ll get what I think you are looking for. I did this exact setup and got the car to fall and stop on the ground-plane with no errors (and even got a bounce and skid to the side messing with the Mass and Bounciness settings). Like I said, without knowing a bit more, specifically, about what you are trying to achieve with the simulation I can’t think of anyway else to do this.
That’s pretty much exactly the effect that I wanted!