koobas.hobune.stream
3D Planatary Gravity
I am using RigidBodies and want my planets to use real physics bases off of their mass and want to have that gravity to interact with other RigidBodies in the system.
Step 1: Turn off gravity
Step 2: Create some kind of 'forcefield' script on your planets. There are a lot of ways of doing this, but the simplest one would be to use Physics.OverlapSphere and then apply forces to everything in that area. Here's a sample:
// Make sure to add the line 'using System.Collections.Generic'
// on the first line of the file
public float forceRadius = 20;
public float gravPower = 9.81f;
void FixedUpdate()
{
// Populate a list of nearby bodies
List<Rigidbody> bodies = new List<Rigidbody>();
foreach(Collider col in Physics.OverlapSphere
(transform.position, forceRadius))
{
if(col.attachedRigidbody != null && !bodies.Contains(col.attachedRigidbody))
{
bodies.Add(col.attachedRigidbody);
}
}
// Now you have your rigidbodies, time to add the force!
foreach(Rigidbody body in bodies)
{
float bodyDist = (body.position - transform.position).sqrMagnitude;
float gravStrengthFactor = Mathf.Pow(forceRadius) / bodyDist;
body.AddForce(gravStrengthFactor * gravPower *
(transform.position - body.position) * Time.deltaTime, ForceMode.Acceleration);
}
}
Of course, there are a whole slew of optimisations you can apply to this, but it's a start.
Step 3: Write a simplified physics engine to simulate interactions between the large 'gravity generator' objects, since they would kind of break themselves if they could affect themselves.
Would applying forces not produce "repulsion" as opposed to attraction? Wouldn't gravity have to do solely about attraction?
What's the difference between 'repulsion' and 'attraction'? The direction of the force, that's what. Have you tried the script? I think there are some issues with the falloff calculation, but the basic concept is sound.
Unity's physics engine only simulates gravity from one gravitational body. The RigidBody objects have a force applied to them in the down (-ve Y) axis only. There is no concept of creating additional gravity fields/forces that would act as attractors to other objects.
