# Best ratio for RigidBodyControl

I want to have my CharacterControl player able to slide a RigidBodyControl chair across a RigidBodyControl hardwood floor with relative ease (and maybe knock the chair over). I know there are at least 3 factors related to this (spatial volume, mass, and friction).

What would be the best ratio of those 3 (and any other major factors) for the player, the chair, and the floor to achieve my objective?

I think it would depend a lot on the collision shape of the chair. Why not experiment and decide for yourself what works best?

well, answer is: there is no Ratio

friction - it depends on external material not volume/mass itself (mass will just multiple effect)
mass - it also depends based on āfrom what is it made?ā
volume - no need tell.

for a chair, it will be 2-4kg ? idk. friction high, like 0.95

Iām just confused about the numbers here.
What is the maximum mass? If I set my player mass to 2f, the chair will wiggle out from under the player, but if I set it less than that, itās too difficult to move the chair.

Mass is effectively kilograms. Units are meters. Set values accordingly and then adjust as needed.

Probably your player has more than 2kg of mass, I guess.

Always start from real-ish values and then adjust to taste from there based on results.

1 Like

If I set the player mass to 5kg and the chair to 1kg, I end up āsteppingā over the chair when I try to push it. When I try to jump onto the chair, the player gets stuck in the roof.

Edit: Iām not very good with kgās, Iām better with lbās

Edit: I switched the chair mass to 3kg, and the problem seemed to get worse.

So your player is a very small dog? Or is it a person?

Edit: P.S.: Iām an American steeped in the rich and deep history of our really messed up āimperialā system of measurement and even I know that the lb to kg conversion is 2.2ā¦ 1kg = 2.2 pounds, so roughly ādoubleā as a rule of thumb.

Itās an full-grown person, but if I increase the mass >=8, I end up fazing thru the roof at the start of the program.

āI messed up one physics problem because another physics problem was messed up.ā

Start from real values. Fix the problems.

Else you will be chasing your tail forever and never get anywhere. Unless you are making a game of styrofoam objects and then the behavior is roughly as expected. Maybe thatās your answer: just texture everything white and pretend they are all made of lighweight foam?

Edit: re: āplayer mass > 10āā¦ this is a picture of my dog:

She weights considerably less than sheād like to in this picture because she thinks she should have second dinnerā¦ but she weights ~34 kg.

5 Likes

The roof, walls, and floor are set to 0kg. I assume thatās the value you set for RigidBodyControl if you want it to be stationary but collide with stuff, because thatās how they did it in the tutorials.

Iāve set the player to 75kg, it still happens the same way as if I was at 10kg. As soon as my player hits the floor, he is teleported on top of the roof, where he can walk around just fine. When I switch to <8kg, the problem goes away.

Iāve also set all my furniture to about the right weights, but the problem still happens when Iām >7kg.

Nice dog!

1 Like

Oof, I thought the step height parameter on the mass parameterā¦
Those errors are most annoyingā¦

Thanks for the info on masses anyway.

sorry i dont read all, but based on first reply, seems like you have wrong "center of mass"

center of mass can be auto-calculated in Blender or other tools.