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fixed constraint torque calculation

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liabru 2017-05-02 23:50:01 +01:00
parent b6e597378e
commit a8d1950148
1 changed files with 15 additions and 49 deletions
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64
src/constraint/Constraint.js
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@ -24,6 +24,7 @@ var Common = require('../core/Common');
var _zeroVector = { x: 0, y: 0 };
Constraint._warming = 0.4;
Constraint._torqueDampen = 0.8;
Constraint._minLength = 0.000001;
/**
@ -120,6 +121,9 @@ var Common = require('../core/Common');
pointA = constraint.pointA,
pointB = constraint.pointB;
if (!bodyA && !bodyB)
return;
// update reference angle
if (bodyA && !bodyA.isStatic) {
Vector.rotate(pointA, bodyA.angle - constraint.angleA, pointA);
@ -141,58 +145,24 @@ var Common = require('../core/Common');
if (!pointAWorld || !pointBWorld)
return;
var velocityPointA = _zeroVector,
velocityPointB = _zeroVector;
if (bodyA && !bodyA.isStatic) {
// update velocity
bodyA.velocity.x = bodyA.position.x - bodyA.positionPrev.x;
bodyA.velocity.y = bodyA.position.y - bodyA.positionPrev.y;
bodyA.angularVelocity = bodyA.angle - bodyA.anglePrev;
// find point velocity and body mass
velocityPointA = Vector.add(bodyA.velocity, Vector.mult(Vector.perp(pointA), bodyA.angularVelocity));
}
if (bodyB && !bodyB.isStatic) {
// update velocity
bodyB.velocity.x = bodyB.position.x - bodyB.positionPrev.x;
bodyB.velocity.y = bodyB.position.y - bodyB.positionPrev.y;
bodyB.angularVelocity = bodyB.angle - bodyB.anglePrev;
// find point velocity and body mass
velocityPointB = Vector.add(bodyB.velocity, Vector.mult(Vector.perp(pointB), bodyB.angularVelocity));
}
var delta = Vector.sub(pointAWorld, pointBWorld),
currentLength = Vector.magnitude(delta);
// prevent singularity
if (currentLength === 0) {
if (currentLength < Constraint._minLength) {
currentLength = Constraint._minLength;
delta.x = Constraint._minLength;
}
// solve distance constraint with Gauss-Siedel method
var difference = (currentLength - constraint.length) / currentLength,
normal = Vector.div(delta, currentLength),
force = Vector.mult(delta, difference * constraint.stiffness * timeScale * timeScale),
relativeVelocity = Vector.sub(velocityPointB, velocityPointA),
stiffness = constraint.stiffness < 1 ? constraint.stiffness * timeScale : constraint.stiffness,
force = Vector.mult(delta, difference * stiffness),
massTotal = (bodyA ? bodyA.inverseMass : 0) + (bodyB ? bodyB.inverseMass : 0),
inertiaTotal = (bodyA ? bodyA.inverseInertia : 0) + (bodyB ? bodyB.inverseInertia : 0),
resistanceTotal = massTotal + inertiaTotal,
normalImpulse = Vector.dot(normal, relativeVelocity) / resistanceTotal,
normalVelocity,
torque,
share;
if (normalImpulse < 0 && constraint.angularStiffness < 1) {
normalVelocity = {
x: normal.x * normalImpulse,
y: normal.y * normalImpulse
};
}
if (bodyA && !bodyA.isStatic) {
share = bodyA.inverseMass / massTotal;
@ -204,12 +174,10 @@ var Common = require('../core/Common');
bodyA.position.x -= force.x * share;
bodyA.position.y -= force.y * share;
if (normalVelocity) {
share = (bodyA.inverseInertia + bodyA.inverseMass) / resistanceTotal;
torque = Vector.cross(pointA, normalVelocity) * share * bodyA.inverseInertia * constraint.stiffness * (1 - constraint.angularStiffness);
bodyA.constraintImpulse.angle += torque;
bodyA.angle += torque;
}
// apply torque
torque = (Vector.cross(pointA, force) / resistanceTotal) * Constraint._torqueDampen * bodyA.inverseInertia;
bodyA.constraintImpulse.angle -= torque;
bodyA.angle -= torque;
}
if (bodyB && !bodyB.isStatic) {
@ -223,12 +191,10 @@ var Common = require('../core/Common');
bodyB.position.x += force.x * share;
bodyB.position.y += force.y * share;
if (normalVelocity) {
share = (bodyB.inverseInertia + bodyB.inverseMass) / resistanceTotal;
torque = Vector.cross(pointB, normalVelocity) * share * bodyB.inverseInertia * constraint.stiffness * (1 - constraint.angularStiffness);
bodyB.constraintImpulse.angle -= torque;
bodyB.angle -= torque;
}
// apply torque
torque = (Vector.cross(pointB, force) / resistanceTotal) * Constraint._torqueDampen * bodyB.inverseInertia;
bodyB.constraintImpulse.angle += torque;
bodyB.angle += torque;
}
};