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added constraint damping

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liabru 2017-06-12 19:53:40 +01:00
parent fe9b05d520
commit 44c4d1ff8d
1 changed files with 44 additions and 3 deletions
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47
src/constraint/Constraint.js
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@ -28,7 +28,8 @@ var Common = require('../core/Common');
/**
* Creates a new constraint.
* All properties have default values, and many are pre-calculated automatically based on other properties.
* To simulate a revolute constraint (or pin joint) set `length: 0` and `stiffness: 1`.
* To simulate a revolute constraint (or pin joint) set `length: 0` and a high `stiffness` value (e.g. `0.7` or above).
* If the constraint is unstable, try lowering the `stiffness` value and / or increasing `engine.constraintIterations`.
* See the properties section below for detailed information on what you can pass via the `options` object.
* @method create
* @param {} options
@ -63,7 +64,8 @@ var Common = require('../core/Common');
constraint.id = constraint.id || Common.nextId();
constraint.label = constraint.label || 'Constraint';
constraint.type = 'constraint';
constraint.stiffness = constraint.stiffness || 1;
constraint.stiffness = constraint.stiffness || (constraint.length > 0 ? 1 : 0.7);
constraint.damping = constraint.damping || 0;
constraint.angularStiffness = constraint.angularStiffness || 0;
constraint.angleA = constraint.bodyA ? constraint.bodyA.angle : constraint.angleA;
constraint.angleB = constraint.bodyB ? constraint.bodyB.angle : constraint.angleB;
@ -177,7 +179,22 @@ var Common = require('../core/Common');
inertiaTotal = (bodyA ? bodyA.inverseInertia : 0) + (bodyB ? bodyB.inverseInertia : 0),
resistanceTotal = massTotal + inertiaTotal,
torque,
share;
share,
normal,
normalVelocity,
relativeVelocity;
if (constraint.damping) {
var zero = Vector.create();
normal = Vector.div(delta, currentLength);
relativeVelocity = Vector.sub(
bodyB && Vector.sub(bodyB.position, bodyB.positionPrev) || zero,
bodyA && Vector.sub(bodyA.position, bodyA.positionPrev) || zero
);
normalVelocity = Vector.dot(normal, relativeVelocity);
}
if (bodyA && !bodyA.isStatic) {
share = bodyA.inverseMass / massTotal;
@ -190,6 +207,12 @@ var Common = require('../core/Common');
bodyA.position.x -= force.x * share;
bodyA.position.y -= force.y * share;
// apply damping
if (constraint.damping) {
bodyA.positionPrev.x -= constraint.damping * normal.x * normalVelocity * share;
bodyA.positionPrev.y -= constraint.damping * normal.y * normalVelocity * share;
}
// apply torque
torque = (Vector.cross(pointA, force) / resistanceTotal) * Constraint._torqueDampen * bodyA.inverseInertia * (1 - constraint.angularStiffness);
bodyA.constraintImpulse.angle -= torque;
@ -207,6 +230,12 @@ var Common = require('../core/Common');
bodyB.position.x += force.x * share;
bodyB.position.y += force.y * share;
// apply damping
if (constraint.damping) {
bodyB.positionPrev.x += constraint.damping * normal.x * normalVelocity * share;
bodyB.positionPrev.y += constraint.damping * normal.y * normalVelocity * share;
}
// apply torque
torque = (Vector.cross(pointB, force) / resistanceTotal) * Constraint._torqueDampen * bodyB.inverseInertia * (1 - constraint.angularStiffness);
bodyB.constraintImpulse.angle += torque;
@ -366,6 +395,18 @@ var Common = require('../core/Common');
* @default 1
*/
/**
* A `Number` that specifies the damping of the constraint,
* i.e. the amount of resistance applied to each body based on their velocities to limit the amount of oscillation.
* Damping will only be apparent when the constraint also has a very low `stiffness`.
* A value of `0.1` means the constraint will apply heavy damping, resulting in little to no oscillation.
* A value of `0` means the constraint will apply no damping.
*
* @property damping
* @type number
* @default 0
*/
/**
* A `Number` that specifies the target resting length of the constraint.
* It is calculated automatically in `Constraint.create` from initial positions of the `constraint.bodyA` and `constraint.bodyB`.