# Physics Entity

Hi,

I have just started working with visual components physics and i’m having some strange behaviors . For example, i have small bottles running on a conveyor with physics, setting dynamic and static friction all works fine until i change the width of the conveyor which is irrelevant, they fall and can’t stand still.

Besides that, any useful documentation to get to know better physics in VC ?

Regards,

Updates will be made to better describe units and property values of Physics Entity behaviors. More tutorials are also being made for physics in 4.0 and the upcoming 4.1.

In your case, I would try adjusting the MaterialDensity of the bottles, e.g. start with a high number and work your way down to find a value that is okay for simulation. Next, if the bottles are approaching the conveyor in a linear motion, set Angular Damping of bottles to 1 and see what happens.

Generally, small objects like bottles have such small mass and surface area that they are all over the place. Some tricks like making them weigh more, applying a damping force, creating a box collider with padding, and adding an invisible block to give them more mass are usually what I try first when troubleshooting.

Here is a quick note about the Physics Entity properties

MaterialDensity kg/m^3
Affects mass of entity

StaticFriction 0-1
Coefficient of friction

DynamicFriction 0-1
Coefficient of friction

Restitution 0-1
Affects bounciness of entity upon collision with other object, e.g. < 1 is less bouncy so less bounce back, whereas 1 is bouncy with bounce back using same speed at time of collision

Linear Damping 0-1
Coefficient of damping. **bug in 4.0 version where this value is used for angular damping

Angular Damping 0-1
Coefficient of damping. ''bug in 4.0 version where this value is used for linear damping

Solver Position Iterations Integer
Used for solving position of entity… more iterations means more accurate position but at a cost of performance… and more iterations might not give better results after a certain point

Solver Velocity Iterations Integer
Used for solving velocity of entity

Scene Id Integer
Used for defining which scene entity belongs to in 3D world… a scene is abstract and more or less a layer… entities in different scenes do not collide with one another… default is 0 and floor of 3D world has a scene id of 0

Collision Group Integer
Used to limit the collision of entity with other objects in its group… so objects can be in same scene/layer… example is human colliding with wall but not forklift or specific nodes of robot that can collide with other objects

Smoothing Steps Integer
Used for smoothing the animation of entity… only use if entity has a lot of motion and the rendering of entity in 3D world is very jagged, e.g. a Physics cable that twists and shows a smooth movement of the twist instead of a jagged animation

You can refer to Nvidia Physx documentation or check Unity doc as well since it also uses Physx engine. Note: Unity refers to damping as “drag”.

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In this simple test, i have randomly falling bottles, and for what concerns damping if i set damping to 1 they fall while on 0 its okay. see attached file.

test-physics.vcmx (67.7 KB)