gravity simulation script

Unity Engine
1

I guys, i have a problem with a gravity simulation script

this is my script:

using UnityEngine;
using System.Collections;

public class gravity : MonoBehaviour {
    public float gravitationalAcceleration;    // on surface
    public float gravityRadius;
    public bool useExternalMass;
    public float distanceVariation = 0;    // variation between the gravity on surface and the gravity at gravityRadius(i.e. 0,5 is half gravity). 0 is no change

    float gravityRadiusInUnit;
    float unitDistanceVariation;
    SphereCollider gravitySphere;

    Vector3 position;

    // Use this for initialization
    void Start() {
        gravitySphere = gameObject.AddComponent<SphereCollider>();
        gravitySphere.isTrigger = true;
        gravitySphere.radius = gravityRadius;
        position = transform.position;
        gravityRadiusInUnit = gravitySphere.radius * transform.localScale.x;
        unitDistanceVariation = distanceVariation / ( gravityRadiusInUnit + transform.localScale.x );
        }

    // Update is called once per frame
    void Update() {
        position = transform.position;
        }

    void OnTriggerStay(Collider other) {
        if( other.attachedRigidbody ) {
            Vector3 otherPosition = other.transform.position;
            Vector3 direction = ( position - otherPosition ).normalized;
            float otherMass = 1;
            if( useExternalMass ) {
                otherMass = other.attachedRigidbody.mass;
                }
            other.attachedRigidbody.AddForce(direction * GravitationAccelerationAtPosition(otherPosition) * otherMass * Time.deltaTime, ForceMode.Acceleration);
            }
        }

    float GravitationAccelerationAtPosition(Vector3 otherPosition) {
        float distanceFromSurface/*  */ = ( otherPosition - position ).magnitude - ( transform.localScale.x / 2 );
        return ( 1 - ( unitDistanceVariation * distanceFromSurface ) ) * gravitationalAcceleration;
        }

    }

The parameters:
gravitationalAcceleration: the gravitational acceleration on the surface
gravityRadius: the radius of the gravity
useExternalMass: if true each gameobject react to gravity according to its mass
distanceVariation: variation between the gravity on surface and the gravity at gravityRadius(i.e. 0,5 is half gravity). 0 is no change

The script must be applied to a sphere.

The script creates a trigger sphere collider that applies a force to each gameobject inside it.

The script works correctly but after the “landing” the object start to “vibrate”, how can I fix this?

P.S.: Sorry for my poor english…

2

if its landed and AdForce is still active it will cause your problem…it will keep pushing

3

Yes, but if I disable the gravity force on the collision with the surface than the object can also stop itself in a strange position(i.e. a cube on a corner)

4

then use a circle collider to keep from getting stuck in a corner,but if you keep adding force its gonna keep pushing the cube no matter what…I know I had the same problem with a player hitting a saw blade…it will keep pushing him away as long as addForce is applied

5

With the circle collider I don’t get the desired effect

I think that the best way would be to stop the gravity force only if the vibrations are below a certain level, in this way the object movement would be real

I try to think a way to quantify the vibrations…

6

Is there a way to see how gravity is implemented in unity?

7

This is why most people just let the physics engine settle objects. This might also be mitigated better with acceleration rather than force.

It uses a constant. Look under edit.

8

I’m already using acceleration
The last parameter of addForce is ForceMode.Acceleration, is this what you mean?

I mean, can i see the code?

9

Right, missed that.

New to unity?
No, it’s closed source. So unless you are aiming to put something in orbit, I would highly suggest getting used to the physics that is already a part of the engine. Otherwise the solution is probably found in spring physics.

10

The problem is that I’m aiming to create something like Angry Birds Space and i would like to reuse the script for other similar project

Anyway, the problem is that after the contact with a planet every object begins to “shake” apparently caused by the force that continues to be applicated, i can stop this after a collision but in this way the object don’t behave correctly

But must there be a solution…