making a cloth collision object turn on and off during an animation

Support Particles and Physics Simulations
1

basically i want to have a collision object that participates with a cloth sim, and then at a certain point in the animation simply disappears, causing the cloth to no longer be affected by it.

in rigid body physics there is a ‘dynamic’ toggle that you can animate on and off to achieve this effect; i’m looking for something equivalent with cloth physics.

i’ve tried simply moving the object away quickly over 1 frame, but the sim still “knows” about this rapid motion and it makes the sim freak out.

i have a hack-y solution where i simulate to the frame where i want the collider to disappear, and with the playhead on that frame, manually turn off the collision modifier and then continue to simulate. i say its hack-y because as soon as i turn off the collision modifier, the simulation cache knows it is out of date and turns light blue, and i have to be very careful to only advance the playhead forwards until i have all the frames i want and can convert the cache to bake.

are there any better techniques for this?

thanks!

2

You can animate cloth collision. Keyframe it selected at the beginning of the animation and then again just before you want it to not be affected by the collision object, advance a frame and keyframe the cloth collision deselected.

3

awesome, thanks! that actually might work for my needs. :slight_smile:

as a thought, i can imagine scenarios where i want the cloth to still be able to collide with certain objects or itself, while animating the collision property with a single object. imagine the case where a ghostly figure causes a sheet to rise up from a surface, but then the figure evaporates away, causing the cloth to collapse back into a pile on the floor.

4

If you want to do that, you just have to move the collision object out of the way when collision is deselected and then select collision again and add a keyframe.