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physics bounce value doesnt work unless both colliding objects have bounce value.
Closed, InvalidPublic

Description

System Information
Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.86

Blender Version
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-07-16 23:38, hash: rB4a5e046c923f
Worked: (optional)

Short description of error
physics bounce value doesnt work unless both objects bounce

Exact steps for others to reproduce the error

open provided file and press play, the ball doesnt bounce even though it's bounce value is set to 1. select the ground plane and then in the physics tab set it's bounce to 1, now the ball does bounce.

I've checked to make sure that i'ts not just the behaviour of passive rigid bodies, and the same problem applies even if both colliding objects are active rigid bodies (one animated so it didnt move).

This makes it impossible for a ball to bounce off of a collapsible brick wall for example, as the bricks would have hardly any bounce of their own so that they can land properly.

Details

Type
Bug

Event Timeline

Sebastian Parborg (zeddb) triaged this task as Confirmed, Medium priority.
Sergej Reich (sergof) closed this task as Invalid.Thu, Jul 25, 8:31 AM

Thanks for the report, but unfortunately this is expected behaviour.
There's different ways of mixing bounciness (restitution) values of two objects you could use.
The formula we use is: restitution_a * restitution_b, which will give you a value of 0 if any of the two is 0.
It's also common to use the maximum of the two values (which imo behaves better and is also what you expected).
If it were up to me, that's what we wold be using. However, that decision has been made a long time ago and changing it now would mean breaking all simulations.
So this is a limitation.