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old.js
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//contains alternate code, what was previously commented out in grav-runge-kutta.js
/*
* Originally in the beginning of resetCanvas
*/
/*
var transition = document.getElementById('transition').getContext('2d');
if (willReset) {
if (antiFlicker || alpha < 1) {
transition.drawImage(paper.canvas, 0, 0);
}
paper.fillStyle = '#000';
paper.fillRect(-oldRect[0], -oldRect[1], oldRect[2], oldRect[3]);
}
paper.setTransform(1, 0, 0, 1, 0, 0);
var scaleWidth = windowWidth / rectDimensions[2];
var scaleHeight = windowHeight / rectDimensions[3];
paper.scale(scaleWidth, scaleHeight);
paper.translate(rectDimensions[0], rectDimensions[1]);
if (willReset && (antiFlicker || alpha < 1)) {
paper.drawImage(transition.canvas, -oldRect[0], -oldRect[1], oldRect[2], oldRect[3]);
}
if (willReset && isPaused) {
for (var i = bodies.length; i--;) {
drawBody(bodies[i].position[0], bodies[i].position[1], bodies[i].radius, bodies[i].color, paper);
}
}
*/
//trying to get a symplectic integrator working
function symplectic(state, derivative, c, d, getEnergy, colliders1, colliders2) {
getEnergy = !!getEnergy;
var getColliders = !!colliders1;
var colliders = {};
var contact = false;
var totalEnergy = 0;
var bodiesLength = state.length;
for (var i = bodiesLength; i--;) {
if (c != 0) {
for (var j = i; j--;) {
var diff = state[i].position.subtract(state[j].position);
if (getColliders) {
var radii = bodies[i].radius + bodies[j].radius;
if (diff.dot(diff) <= (radii*radii)) {
if (!colliders[i]) {
colliders[i] = [];
}
if (!colliders[j]) {
colliders[j] = [];
}
if (!(colliders[i].indexOf(j) > 0 || colliders[j].indexOf(i) > 0)) {
if (bodies[i].mass > bodies[j].mass) {
colliders[i][colliders[i].length] = j;
} else {
colliders[j][colliders[j].length] = i;
}
contact = true;
}
}
}
var dist = state[i].position.distanceFrom(state[j].position);
var mult = gravConstant / (dist * dist* dist);
var multj = -mult * bodies[j].mass;
var multi = mult * bodies[i].mass;
var momentumi = [];
if (!state[i].momentum) {
momentumi = state[i].velocity.multiply(bodies[i].mass);
} else {
momentumi = state[i].momentum;
}
var momentumj = [];
if (!state[j].momentum) {
momentumj = state[j].velocity.multiply(bodies[j].mass);
} else {
momentumj = state[j].momentum;
}
derivative[i].momentum = derivative[i].momentum.add(momentumi.subtract(diff.multiply(multi * c)));
derivative[j].momentum = derivative[j].momentum.add(momentumj.subtract(diff.multiply(multj * c)));
if (counts == 100) {
debug("i: " + i);
debug("j: " + j);
debug(derivative[i].momentum);
debug(derivative[j].momentum);
debug(diff);
}
if (getEnergy) {
totalEnergy -= (gravConstant * bodies[j].mass * bodies[i].mass) / state[i].position.distanceFrom(state[j].position);
}
}
} else {
var momentum = [];
if (!state[i].momentum) {
momentum = state[i].velocity.multiply(bodies[i].mass);
} else {
momentum = state[i].momentum;
}
derivative[i].momentum = momentum;
}
}
for (var i = bodiesLength; i--;) {
derivative[i].position = state[i].position.add(derivative[i].momentum.multiply(d));
}
/*
for (var i = bodiesLength; i--;) {
var momentum = [];
if (!state[i].momentum) {
momentum = state[i].velocity.multiply(bodies[i].mass);
} else {
momentum = state[i].momentum;
}
derivative[i].position = state[i].position.add(momentum.multiply(c/bodies[i].mass));
}
for (var i = bodiesLength; i--;) {
for (var j = i; j--;) {
var diff = derivative[i].position.subtract(derivative[j].position);
if (getColliders) {
diff = state[i].position.subtract(state[j].position);
var radii = bodies[i].radius + bodies[j].radius;
if (diff.dot(diff) <= (radii*radii)) {
if (!colliders[i]) {
colliders[i] = [];
}
if (!colliders[j]) {
colliders[j] = [];
}
if (!(colliders[i].indexOf(j) > 0 || colliders[j].indexOf(i) > 0)) {
if (bodies[i].mass > bodies[j].mass) {
colliders[i][colliders[i].length] = j;
} else {
colliders[j][colliders[j].length] = i;
}
contact = true;
}
}
}
var dist = derivative[i].position.distanceFrom(derivative[j].position);
var mult = gravConstant / (dist * dist * dist);
var multj = -mult * bodies[j].mass;
var multi = mult * bodies[i].mass;
var momentumi = [];
if (!state[i].momentum) {
momentumi = state[i].velocity.multiply(bodies[i].mass);
} else {
momentumi = state[i].momentum;
}
var momentumj = [];
if (!state[j].momentum) {
momentumj = state[j].velocity.multiply(bodies[j].mass);
} else {
momentumj = state[j].momentum;
}
derivative[i].momentum = derivative[i].momentum.add(momentumi.subtract(diff.multiply(multi * d)));
derivative[j].momentum = derivative[j].momentum.add(momentumj.subtract(diff.multiply(multj * d)));
if (getEnergy) {
totalEnergy -= (gravConstant * bodies[j].mass * bodies[i].mass) / state[i].position.distanceFrom(state[j].position);
}
}
}
*/
if (contact) {
for (var first in colliders) {
colliders1[colliders1.length] = +first;
colliders2[colliders2.length] = colliders[first];
}
}
return totalEnergy;
}
/*
* Previously in calculateOrbit, before the part that erases the screen (alpha >= 0.001)
*/
// Symplectic Integration
// This symplectic integrator based on method outlined in "Symplectic Integrators and their Application to Dynamical Astronomy"
// by Hiroshi Kinoshita, Haruo Yoshida, and Hiroshi Nakai (1990)
/*
var derivative1 = [];
var derivative2 = [];
var derivative3 = [];
var derivative4 = [];
for (var i = bodiesLength; i--;) {
derivative1[i] = {position:[0,0], momentum:[0,0]};
derivative2[i] = {position:[0,0], momentum:[0,0]};
derivative3[i] = {position:[0,0], momentum:[0,0]};
derivative4[i] = {position:[0,0], momentum:[0,0]};
}
var massiveColliders = [];
var smallColliders = [];
var energy;
var beta = Math.pow(2, 1/3);
var symInput = (beta + (1/beta) - 1) / 6;
if (isBounce) {
//energy = symplectic(bodies, derivative1, 1/(2*(2-beta)), 1/(2-beta), true, massiveColliders, smallColliders);
//energy = symplectic(bodies, derivative1, symInput + .5, (2*symInput) + 1, true, massiveColliders, smallColliders);
energy = symplectic(bodies, derivative1, 0, symInput + .5, true, massiveColliders, smallColliders);
} else {
//energy = symplectic(bodies, derivative1, 1/(2*(2-beta)), 1/(2-beta), true);
//energy = symplectic(bodies, derivative1, symInput + .5, (2*symInput) + 1, true);
energy = symplectic(bodies, derivative1, 0, symInput + .5, true);
}
/*
symplectic(derivative1, derivative2, (1-beta)/(2*(2-beta)), -beta/(2-beta));
symplectic(derivative2, derivative3, (1-beta)/(2*(2-beta)), 1/(2-beta));
*/
/*
symplectic(derivative1, derivative2, (2*symInput) + 1, -symInput);
symplectic(derivative2, derivative3, (-4*symInput) - 1, -symInput);
symplectic(derivative3, derivative4, (2*symInput) + 1, symInput + .5);
*/
/*
* In the conditional for checking if colliding
*/
/*
// for absorbing
for (var i = massiveColliders.length; i--;) {
var newMass = bodies[massiveColliders[i]].mass + bodies[smallColliders[i]].mass;
var newRadius = Math.pow((newMass) / 2.50596227828973444312e20, 1/2); // using average density of all planets of 3.1251e3 kg / m
//newRadius /= 1e5; // 1px = 1e-5 m
if (newRadius < 100) {
newRadius = 100;
}
var newVelocity = bodies[massiveColliders[i]].velocity.multiply(bodies[massiveColliders[i]].mass).add(bodies[smallColliders[i]].velocity.multiply(bodies[smallColliders[i]].mass)).multiply(1/newMass);
bodies[massiveColliders[i]].mass = newMass;
bodies[massiveColliders[i]].radius = newRadius;
bodies[massiveColliders[i]].velocity = newVelocity;
}
// remove the small body and all its derivatives
var minimum = bodies.length;
var subtract = 0;
for (var i = smallColliders.length; i--;) {
var index = smallColliders[i];
if (index < minimum) {
// the index now references bodies of one lower index
subtract++;
minimum = index;
} else {
index -= subtract;
}
bodies.splice(index, 1);
derivative1.splice(index, 1);
derivative3.splice(index, 1);
derivative4.splice(index, 1);
}
*/
/*
* In loop that updates bodies position and velocities, forgot why it's there
*/
/*
bodies[i].position = derivative3[i].position.add(derivative3[i].momentum.multiply(1/(2*bodies[i].mass*(2-beta))));
bodies[i].velocity = derivative3[i].momentum.multiply(1/bodies[i].mass);
*/
/*
bodies[i].position = derivative1[i].position;
bodies[i].velocity = derivative1[i].momentum.multiply(1/bodies[i].mass);
*/
/*
bodies[i].position = derivative4[i].position;
bodies[i].velocity = derivative4[i].momentum.multiply(1/bodies[i].mass);
*/