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code simplification #2

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93 changes: 33 additions & 60 deletions src/collision/Resolver.js
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Original file line number Diff line number Diff line change
Expand Up @@ -232,65 +232,38 @@ var Bounds = require('../geometry/Bounds');
restingThresh = Resolver._restingThresh,
restingThreshTangent = Resolver._restingThreshTangent,
frictionNormalMultiplier = Resolver._frictionNormalMultiplier;

for (var i = 0; i < pairs.length; i++) {
var pair = pairs[i];

if (!pair.isActive || pair.isSensor)
continue;

var collision = pair.collision,
bodyA = collision.parentA,
bodyB = collision.parentB,
normal = collision.normal,
normalX = normal.x,
normalY = normal.y,
tangent = collision.tangent,
tangentX = tangent.x,
tangentY = tangent.y,
contacts = pair.activeContacts,
contactShare = 1 / contacts.length;
contactShare = 1 / pair.activeContacts.length;

// update body velocities
var positionA = bodyA.position,
positionAX = positionA.x,
positionAY = positionA.y,
positionB = bodyB.position,
positionBX = positionB.x,
positionBY = positionB.y,
velocityAX = positionAX - bodyA.positionPrev.x,
velocityAY = positionAY - bodyA.positionPrev.y,
velocityBX = positionBX - bodyB.positionPrev.x,
velocityBY = positionBY - bodyB.positionPrev.y,
angularVelocityA = bodyA.angle - bodyA.anglePrev,
angularVelocityB = bodyB.angle - bodyB.anglePrev;

bodyA.velocity.x = velocityAX;
bodyA.velocity.y = velocityAY;
bodyB.velocity.x = velocityBX;
bodyB.velocity.y = velocityBY;

bodyA.angularVelocity = angularVelocityA;
bodyB.angularVelocity = angularVelocityB;

var inverseMassA = bodyA.inverseMass,
inverseMassB = bodyB.inverseMass,
inverseInertiaA = bodyA.inverseInertia,
inverseInertiaB = bodyB.inverseInertia;
bodyA.velocity.x = bodyA.position.x - bodyA.positionPrev.x;
bodyA.velocity.y = bodyA.position.y - bodyA.positionPrev.y;
bodyB.velocity.x = bodyB.position.x - bodyB.positionPrev.x;
bodyB.velocity.y = bodyB.position.y - bodyB.positionPrev.y;
bodyA.angularVelocity = bodyA.angle - bodyA.anglePrev;
bodyB.angularVelocity = bodyB.angle - bodyB.anglePrev;

// resolve each contact
for (var j = 0; j < contacts.length; j++) {
var contact = contacts[j],
contactVertex = contact.vertex,
offsetAX = contactVertex.x - positionAX,
offsetAY = contactVertex.y - positionAY,
offsetBX = contactVertex.x - positionBX,
offsetBY = contactVertex.y - positionBY,
relativeVelocityX = (velocityAX - offsetAY * angularVelocityA) - (velocityBX - offsetBY * angularVelocityB),
relativeVelocityY = (velocityAY + offsetAX * angularVelocityA) - (velocityBY + offsetBX * angularVelocityB),
normalVelocity = normalX * relativeVelocityX + normalY * relativeVelocityY;

var tangentVelocity = tangentX * relativeVelocityX + tangentY * relativeVelocityY,
for (var j = 0; j < pair.activeContacts.length; j++) {
var contact = pair.activeContacts[j],
offsetAX = contact.vertex.x - bodyA.position.x,
offsetAY = contact.vertex.y - bodyA.position.y,
offsetBX = contact.vertex.x - bodyB.position.x,
offsetBY = contact.vertex.y - bodyB.position.y,
relativeVelocityX = (bodyA.velocity.x - offsetAY * bodyA.angularVelocity) - (bodyB.velocity.x - offsetBY * bodyB.angularVelocity),
relativeVelocityY = (bodyA.velocity.y + offsetAX * bodyA.angularVelocity) - (bodyB.velocity.y + offsetBX * bodyB.angularVelocity),
normalVelocity = collision.normal.x * relativeVelocityX + collision.normal.y * relativeVelocityY;

var tangentVelocity = collision.tangent.x * relativeVelocityX + collision.tangent.y * relativeVelocityY,
tangentSpeed = Math.abs(tangentVelocity),
tangentVelocityDirection = Common.sign(tangentVelocity);

Expand All @@ -311,9 +284,9 @@ var Bounds = require('../geometry/Bounds');
}

// modify impulses accounting for mass, inertia and offset
var oAcN = offsetAX * normalY - offsetAY * normalX,
oBcN = offsetBX * normalY - offsetBY * normalX,
share = contactShare / (inverseMassA + inverseMassB + inverseInertiaA * oAcN * oAcN + inverseInertiaB * oBcN * oBcN);
var oAcN = offsetAX * collision.normal.y - offsetAY * collision.normal.x,
oBcN = offsetBX * collision.normal.y - offsetBY * collision.normal.x,
share = contactShare / (bodyA.inverseMass + bodyB.inverseMass + bodyA.inverseInertia * oAcN * oAcN + bodyB.inverseInertia * oBcN * oBcN);

normalImpulse *= share;
tangentImpulse *= share;
Expand Down Expand Up @@ -343,20 +316,20 @@ var Bounds = require('../geometry/Bounds');
}

// total impulse from contact
var impulseX = (normalX * normalImpulse) + (tangentX * tangentImpulse);
var impulseY = (normalY * normalImpulse) + (tangentY * tangentImpulse);
var impulseX = (collision.normal.x * normalImpulse) + (collision.tangent.x * tangentImpulse);
var impulseY = (collision.normal.y * normalImpulse) + (collision.tangent.y * tangentImpulse);

// apply impulse from contact
if (!(bodyA.isStatic || bodyA.isSleeping)) {
bodyA.positionPrev.x += impulseX * inverseMassA;
bodyA.positionPrev.y += impulseY * inverseMassA;
bodyA.anglePrev += (offsetAX * impulseY - offsetAY * impulseX) * inverseInertiaA;
bodyA.positionPrev.x += impulseX * bodyA.inverseMass;
bodyA.positionPrev.y += impulseY * bodyA.inverseMass;
bodyA.anglePrev += (offsetAX * impulseY - offsetAY * impulseX) * bodyA.inverseInertia;
}

if (!(bodyB.isStatic || bodyB.isSleeping)) {
bodyB.positionPrev.x -= impulseX * inverseMassB;
bodyB.positionPrev.y -= impulseY * inverseMassB;
bodyB.anglePrev -= (offsetBX * impulseY - offsetBY * impulseX) * inverseInertiaB;
bodyB.positionPrev.x -= impulseX * bodyB.inverseMass;
bodyB.positionPrev.y -= impulseY * bodyB.inverseMass;
bodyB.anglePrev -= (offsetBX * impulseY - offsetBY * impulseX) * bodyB.inverseInertia;
}
}
}
Expand Down