14-11-2019, 03:16 PM
(14-11-2019, 12:52 PM)josemendez Wrote: Here's a complete example with all the bells and whistles. You can also find it attached for convenience.
Code:using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using Obi;
/**
* Sample component that makes a collider "grab" any particle it touches (regardless of which Actor it belongs to).
*/
[RequireComponent(typeof(ObiCollider))]
public class Grabber : MonoBehaviour
{
public ObiSolver solver;
/**
* Helper class that stores the index of a particle in the solver, its position in the grabber's local space, and its inverse mass previous to being grabbed.
* This makes it easy to tell if a particle has been grabbed, update its position while grabbing, and restore its mass after being released.
*/
private class GrabbedParticle : IEqualityComparer<GrabbedParticle>
{
public int index;
public float invMass;
public Vector3 localPosition;
public GrabbedParticle(int index, float invMass)
{
this.index = index;
this.invMass = invMass;
}
public bool Equals(GrabbedParticle x, GrabbedParticle y)
{
return x.index == y.index;
}
public int GetHashCode(GrabbedParticle obj)
{
return index;
}
}
private Obi.ObiSolver.ObiCollisionEventArgs collisionEvent; /**< store the current collision event*/
private ObiCollider localCollider; /**< the collider on this gameObject.*/
private HashSet<GrabbedParticle> grabbedParticles = new HashSet<GrabbedParticle>(); /**< set to store all currently grabbed particles.*/
private HashSet<ObiSoftbody> grabbedSoftbodies = new HashSet<ObiSoftbody>(); /**< set of softbodies grabbed during this step.*/
private Matrix4x4 grabber2Solver;
private Matrix4x4 solver2Grabber;
private void Awake()
{
localCollider = GetComponent<ObiCollider>();
}
private void OnEnable()
{
solver.OnCollision += Solver_OnCollision;
}
private void OnDisable()
{
solver.OnCollision -= Solver_OnCollision;
}
private void Solver_OnCollision(object sender, Obi.ObiSolver.ObiCollisionEventArgs e)
{
// Calculate transform matrix from grabber to world space (Note: if using local space simulation, postmultiply with solver.transform.localToWorldMatrix)
solver2Grabber = transform.worldToLocalMatrix;
// and its inverse:
grabber2Solver = solver2Grabber.inverse;
collisionEvent = e;
}
private void UpdateRestShapeMatching()
{
// Update rest shape matching of all grabbed softbodies:
foreach (ObiSoftbody softbody in grabbedSoftbodies)
foreach (ObiShapeMatchingConstraintBatch batch in softbody.ShapeMatchingConstraints.GetBatches())
Oni.CalculateRestShapeMatching(solver.OniSolver, batch.OniBatch);
}
/**
* Creates and stores a GrabbedParticle from the particle at the given index.
* Returns true if we sucessfully grabbed a particle, false if the particle was already grabbed.
*/
private bool GrabParticle(int index)
{
GrabbedParticle p = new GrabbedParticle(index, solver.invMasses[index]);
// in case this particle has not been grabbed yet:
if (!grabbedParticles.Contains(p))
{
// record the particle's position relative to the grabber, and store it.
p.localPosition = solver2Grabber.MultiplyPoint3x4(solver.positions[index]);
grabbedParticles.Add(p);
// Set inv mass and velocity to zero:
solver.invMasses[index] = 0;
solver.velocities[index] = Vector4.zero;
return true;
}
return false;
}
/**
* Grabs all particles currently touching the grabber.
*/
public void Grab()
{
grabbedSoftbodies.Clear();
foreach (Oni.Contact contact in collisionEvent.contacts)
{
// this one is an actual collision:
if (contact.distance < 0.01f)
{
Component contactCollider;
if (ObiCollider.idToCollider.TryGetValue(contact.other, out contactCollider))
{
// if the current contact references our collider, proceed to grab the particle.
if (contactCollider == localCollider.SourceCollider)
{
// try to grab the particle, if not already grabbed.
if (GrabParticle(contact.particle))
{
// we want to know if we grabbed a softbody, to update its rest shape.
var softbody = solver.particleToActor[contact.particle].actor as ObiSoftbody;
if (softbody != null)
grabbedSoftbodies.Add(softbody);
}
}
}
}
}
UpdateRestShapeMatching();
}
/**
* Releases all currently grabbed particles. This boils down to simply resetting their invMass.
*/
public void Release()
{
// Restore the inverse mass of all grabbed particles, so dynamics affect them.
foreach (GrabbedParticle p in grabbedParticles)
solver.invMasses[p.index] = p.invMass;
grabbedParticles.Clear();
// Also update rest shape matching:
UpdateRestShapeMatching();
grabbedSoftbodies.Clear();
}
/**
* Updates the position of the grabbed particles.
*/
private void FixedUpdate()
{
foreach (GrabbedParticle p in grabbedParticles)
solver.positions[p.index] = grabber2Solver.MultiplyPoint3x4(p.localPosition);
}
/**
* Just for convenience. Ideally, this should not be part of this component.
* You're expected to control the Grabber from outside.
*/
public void Update()
{
if (Input.GetKeyDown(KeyCode.G))
{
Grab();
}
if (Input.GetKeyDown(KeyCode.R))
{
Release();
}
}
}
It is a component that you can add to any ObiCollider, and it takes a reference to a ObiSolver as input.
It has two methods: Grab() and Release():
- Grab() detects all particles in touch with the collider, stores them in a set together with their invMass and local space position. Then sets its invMass and velocity to zero. Also updates rest shape matching in case any of the particles belonged to a softbody.
- Release() resets all the currently grabbed particle's invMass to whatever it was before grabbing them. This makes them be driven by dynamics once again.
I've included code in Update() that calls Grab() upon pressing "G" in the keyboard, and Release() when pressing "R", for demonstration purposes. Modify it to your taste.
Edit: a video of it in action:
Awesome! Thanks! Could you add it to the store package?