# How to add or use 3 pivot o center on rotation

Hello as you seen in the photo below, I want to make the animation of the scale.I want to make the cube as a active Rigid boby & when i press play animation the cube should move down for gravity and the plate of the scale is A passive rigid body so that the cube will be stop on it and in that moment the scale should move becoz of the weight of the cube and the motion should have point of rotation those called center ,pivot1 ,pivot2 .Is it possible to do so ,or Have to make the animation of the wight scale moving using the location transformation ?

It's possible to do what you want. The plate should not be a passive body though.

Start with the scale. We will need four rigid bodies: the two plates and the arm, all of which move, and an anchor for the arm, so that it will rotate rather than fall. We will need three rigid body constraints, one for each pivot point:

The rigid body constraints are point-type, as demonstrated in the properties viewport. Each joins a pair of rigid bodies and is located at the pivot point. The origins of rigid bodies are used as their center of gravity, and so here, the origins need to be placed carefully, particularly the origin of the crossarm, which needs to be located at the same position as the "center" joint.

The anchoring rigid body should be either passive or animated. With its placement as I have here, I need to leave the default "disable collisions" on the "center" rigid body constraint. All other rigid bodies should be the default "dynamic".

To work like a scale, the "pivot" rigid body constraints need to be directly above their corresponding plates, and equal distances from "center". I have changed the mass of one of the plates here to demonstrate its effect.

You may wish to replace "center" joint with a generic spring type constraint in order to create some damping and resistance to the rotation, which will otherwise rotate the crossarm to the vertical with any difference in weight.

If we want to drop a cube on top of the plate, we can:

We simply create a new rigid body, without any constraints, and drop it onto the plate. I'm showing the original, "rest" state of the system to the left.

• Thank you very much .I wish you shared the bleder file also, hope you don't mind. Thank you once again. Commented Sep 16, 2022 at 22:57
• Sorry, I don't think I bothered saving it. If you're having problems with implementation, it would be best to mention exactly what you're trying and what's going wrong in the question. Commented Sep 16, 2022 at 23:35
• From What I understood from your suggetions , I made this in the link (github.com/kebab03/WeightScale) please tell me what should me corrected?Will be waiting for your answer. Commented Sep 16, 2022 at 23:59
• Your rigid body constraints need to link your rigid body objects together, not your other RB constraints. Commented Sep 17, 2022 at 4:20
• Kindly make the changes on my model and then share the modified file or the screenshot of that .Thank you for your kindness. Commented Sep 17, 2022 at 6:31