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fixed issues with friction stability

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liabru 2015-12-23 12:45:11 +00:00
parent 3de9d00b8e
commit 1db98a3e86
1 changed files with 20 additions and 11 deletions
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31
src/collision/Resolver.js
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@ -16,6 +16,7 @@ var Bounds = require('../geometry/Bounds');
(function() {
Resolver._restingThresh = 4;
Resolver._restingThreshTangent = 6;
Resolver._positionDampen = 0.9;
Resolver._positionWarming = 0.8;
Resolver._frictionNormalMultiplier = 5;
@ -281,37 +282,45 @@ var Bounds = require('../geometry/Bounds');
maxFriction = Infinity;
if (tangentSpeed > pair.friction * pair.frictionStatic * normalForce * timeScaleSquared) {
tangentImpulse = pair.friction * tangentVelocityDirection * timeScaleSquared;
maxFriction = tangentSpeed;
tangentImpulse = Common.clamp(
pair.friction * tangentVelocityDirection * timeScaleSquared,
-maxFriction, maxFriction
);
}
// modify impulses accounting for mass, inertia and offset
var oAcN = Vector.cross(offsetA, normal),
oBcN = Vector.cross(offsetB, normal),
denom = bodyA.inverseMass + bodyB.inverseMass + bodyA.inverseInertia * oAcN * oAcN + bodyB.inverseInertia * oBcN * oBcN;
share = contactShare / (bodyA.inverseMass + bodyB.inverseMass + bodyA.inverseInertia * oAcN * oAcN + bodyB.inverseInertia * oBcN * oBcN);
normalImpulse *= contactShare / denom;
tangentImpulse *= contactShare / (1 + denom);
normalImpulse *= share;
tangentImpulse *= share;
// handle high velocity and resting collisions separately
if (normalVelocity < 0 && normalVelocity * normalVelocity > Resolver._restingThresh * timeScaleSquared) {
// high velocity so clear cached contact impulse
// high normal velocity so clear cached contact normal impulse
contact.normalImpulse = 0;
contact.tangentImpulse = 0;
} else {
// solve resting collision constraints using Erin Catto's method (GDC08)
// impulse constraint, tends to 0
// impulse constraint tends to 0
var contactNormalImpulse = contact.normalImpulse;
contact.normalImpulse = Math.min(contact.normalImpulse + normalImpulse, 0);
normalImpulse = contact.normalImpulse - contactNormalImpulse;
// tangent impulse, tends to -maxFriction or maxFriction
}
// handle high velocity and resting collisions separately
if (tangentVelocity * tangentVelocity > Resolver._restingThreshTangent * timeScaleSquared) {
// high tangent velocity so clear cached contact tangent impulse
contact.tangentImpulse = 0;
} else {
// solve resting collision constraints using Erin Catto's method (GDC08)
// tangent impulse tends to -tangentSpeed or +tangentSpeed
var contactTangentImpulse = contact.tangentImpulse;
contact.tangentImpulse = Common.clamp(contact.tangentImpulse + tangentImpulse, -maxFriction, maxFriction);
tangentImpulse = contact.tangentImpulse - contactTangentImpulse;
}
// total impulse from contact
impulse.x = (normal.x * normalImpulse) + (tangent.x * tangentImpulse);
impulse.y = (normal.y * normalImpulse) + (tangent.y * tangentImpulse);