Hello! I’m using Unreal to create videos of inanimate objects (e.g. a stool) rolling along a pre-defined path and with a pre-defined speed change, and am having trouble at the rendering stage. I would greatly appreciate any help with troubleshooting.
I’m using a Blueprint to be able to apply the same motion trajectory to various different objects. In terms of the rolling animation, I’ve implemented a sort of ‘car body and wheel’ mechanism with physics constraints, where a ‘mover’ cube acts like the car body, and the object I want to roll acts like the wheel. I have two physics constraints binding these two: (1) a suspension that keeps the object (‘wheel’) anchored to the mover (‘car body’), and (2) a rotational axis that allows the object to only rotate in one axis, because the path is straight. Simulate Physics and Gravity are turned off for the mover (a floating cube) and on for the object.
Here’s a screenshot of what this looks like :
Then in the Event Graph, I use a timeline that reads values off a pre-defined distance curve, which then gets converted into a location along the spline path and then is fed into a “Set World Location” node for the mover object.
When I place this in the environment, I make sure that the object is touching the floor or slightly under the floor so that as it gets dragged along with the mover, it can roll. This has worked well for all the simulations I’ve run, but the problem appears when I try to render. No matter what object I use, the object will go flying around in the environment.
Here’s an example - please excuse the poor quality, it’s a quick render sample.
I’ve seen in other posts that it may be due to collision, which I’ve played around with - for example, I’ve noticed that when the object is taken off the ground, it renders fine, except that it won’t roll so that’s not desirable. I’ve also noticed that when the physics constraints overlap with the object, even if the object is taken off the ground, the rendering problem appears again. So In the video above, I have the physics constraints placed on each side of the object so that none of them are overlapping. I don’t think it’s a collision issue between the two constraint bodies, since the mover is far from the object already.
Again, I’ve been troubleshooting for a while now so any help would be greatly appreciated!! Thanks for reading a long post also. Cheers!