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/// <reference path="../../scripts/jquery-3.5.1.min.js"/>
/// <reference path="../../_shared/math/vec2.js" />
/// <reference path="../../_shared/math/mat4.js" />
/// <reference path="../../_shared/2d/shader.js" />
/// <reference path="../../_shared/math/circle.js" />
/// <reference path="../../_shared/2d/program_common.js" />
(function() {
// Define Constants
const GRAVITY = 50.0;
const COF_OF_RESTITUITION = 0.9;
var lProgramContext = undefined;
function main() {
lProgramContext = getContext('#rigidbody_3b');
if (lProgramContext.gl === null) {
console.error('Unable to initialize WebGL. Your browser or machine may not support it.');
return;
}
lProgramContext.gl.clearColor(0.0, 0.0, 0.0, 1.0);
lProgramContext.gl.clear(lProgramContext.gl.COLOR_BUFFER_BIT);
lProgramContext.playButton.on('click', run);
}
function run() {
console.log('Running Rigid Body 3b');
lProgramContext.load().then(function(pProgramInfo) {
const lNumHorizontalPegs = lProgramContext.width / 80.0,
lNumVerticalPegs = lProgramContext.height / 80.0,
lBall = circle(lProgramContext.gl, 16.0, 16,
[ { x: 1, y: 0, z: 0, w: 1 }, { x: 0, y: 1, z: 0, w: 1 }, { x: 0, y: 0, z: 1, w: 1 } ],
vec2(38 * 8, lProgramContext.height - 24.0), 10.0),
lPegList = [];
lBall.velocity = vec2(0, -50.0);
// Generate a peg. These pegs will NOT be updated, so that they
// dont' fall due to gravity.
for (let lRowIdx = 0; lRowIdx < lNumVerticalPegs - 1; lRowIdx++) {
for (let lColIdx = 0; lColIdx <= lNumHorizontalPegs; lColIdx++) {
lPegList.push(circle(lProgramContext.gl,
16.0, 16,
[ { x: 165.0 / 255.0, y: 42.0 / 255.0, z: 42.0 / 255.0, w: 1.0 }],
vec2((lRowIdx % 2 ? 40 : 0) + (lColIdx) * 80.0, lRowIdx * 80.0),
10000 // Real big so it's almost negligble
));
}
}
function updateCircle(pCircle, pDeltaTimeSeconds) {
// Same physics updates from part 1
applyForce(pCircle, vec2(0, -1.0 * (pCircle.mass * GRAVITY)));
const lCurrentAcceleration = scaleVec2(pCircle.force, 1.0 / pCircle.mass);
pCircle.prevVelocity = pCircle.velocity;
pCircle.velocity = addVec2(pCircle.velocity, scaleVec2(lCurrentAcceleration, pDeltaTimeSeconds));
pCircle.prevPos = { ...pCircle.position };
pCircle.position = addVec2(pCircle.position, scaleVec2(pCircle.velocity, pDeltaTimeSeconds));
pCircle.force = vec2();
// Same physics updates from part 2
const lMomentOfInertia = getCircleMomentOfInertia(pCircle);
const lAngularAcceleration = pCircle.torque / lMomentOfInertia;
pCircle.rotationVelocity += lAngularAcceleration * pDeltaTimeSeconds;
pCircle.rotationRadians += pCircle.rotationVelocity * pDeltaTimeSeconds;
pCircle.torque = 0;
pCircle.model = rotateMatrix2d(translateMatrix(mat4(), pCircle.position.x, pCircle.position.y, 0), pCircle.rotationRadians);
}
function update(pDeltaTimeSeconds) {
updateCircle(lBall, pDeltaTimeSeconds);
collision(pDeltaTimeSeconds);
render();
}
function collision(pDeltaTimeSeconds) {
for (let lPegIdx = 0; lPegIdx < lPegList.length; lPegIdx++) {
const lPeg = lPegList[lPegIdx];
if (!doCirclesIntersect(lPeg, lBall)) {
continue;
}
// We have an intersection! Let's try and figure out precisely when that happened.
let lSubdividedDeltaTime = pDeltaTimeSeconds;
// Create a ball and move it back to the balls previous position
let lSubdividedBall = undefined;
do {
// Move the subdivided ball back to the previous position, and then
// advance its position by increasingly smaller timestep. This could be pretty
// slow in some circumstances, and it most definitely does not prevent tunneling,
// but - for now - this is not so bad.
lSubdividedBall = JSON.parse(JSON.stringify(lBall));
lSubdividedBall.position = {...lBall.prevPos};
lSubdividedBall.velocity = {...lBall.prevVelocity};
lSubdividedDeltaTime = lSubdividedDeltaTime / 2.0;
updateCircle(lSubdividedBall, lSubdividedDeltaTime);
if (lSubdividedDeltaTime === 0) {
console.error('This should NOT be happening');
break;
}
} while (doCirclesIntersect(lPeg, lSubdividedBall))
// The ball is no longer intersecting at the time presented here. That means this is
// (nearly) the precise point of intersection.
const lIntersectionResult = getIntersectionDataForCircles(lPeg, lSubdividedBall);
const lRelativeVelocity = lIntersectionResult.relativeVelocity,
lCollisionNormal = lIntersectionResult.collisionNormal,
lFirstPerp = getPerp2(lIntersectionResult.firstPointOfApplication),
lSecondPerp = getPerp2(lIntersectionResult.secondPointOfApplication);
const lNumerator = dot2(scaleVec2(lRelativeVelocity, -(1.0 + COF_OF_RESTITUITION)), lCollisionNormal);
const lLinearDenomPart = dot2(lCollisionNormal, (scaleVec2(lCollisionNormal, 1 / lBall.mass)));
const lRotationalDenomPart = (Math.pow(dot2(lFirstPerp, lCollisionNormal), 2) / getCircleMomentOfInertia(lPeg))
+ (Math.pow(dot2(lSecondPerp, lCollisionNormal), 2) / getCircleMomentOfInertia(lBall))
const lImpulseMagnitude = lNumerator / (lLinearDenomPart + lRotationalDenomPart);
lBall.position = lSubdividedBall.position; // Move the ball back to its proper subdivided position
lBall.velocity = subVec2(lBall.velocity, scaleVec2(lCollisionNormal, lImpulseMagnitude / lBall.mass));
lBall.rotationVelocity = lBall.rotationVelocity - dot2(lSecondPerp, scaleVec2(lCollisionNormal, lImpulseMagnitude)) / getCircleMomentOfInertia(lBall);
// Now we update in our new direction with the remaining time that we have left.
updateCircle(lBall, pDeltaTimeSeconds - lSubdividedDeltaTime);
break;
}
}
function render() {
lProgramContext.gl.clearColor(0.0, 0.0, 0.0, 1.0);
lProgramContext.gl.clearDepth(1.0);
lProgramContext.gl.enable(lProgramContext.gl.DEPTH_TEST);
lProgramContext.gl.depthFunc(lProgramContext.gl.LEQUAL);
lProgramContext.gl.clear(lProgramContext.gl.COLOR_BUFFER_BIT | lProgramContext.gl.DEPTH_BUFFER_BIT);
lProgramContext.gl.useProgram(pProgramInfo.program);
lProgramContext.gl.uniformMatrix4fv(pProgramInfo.uniformLocations.projection, false, lProgramContext.perspective);
lPegList.forEach(function(pCircle) {
renderCircle(lProgramContext.gl, pProgramInfo, pCircle);
});
renderCircle(lProgramContext.gl, pProgramInfo, lBall);
}
const TORQUE_MULTIPLIER = 100.0; // TODO: This may be unncessary
function applyForce(pCircle, pForceVector, pPointOfApplication) {
if (pPointOfApplication !== undefined) {
const lOriginToPointOfApp = subVec2(vec2(), pPointOfApplication),
lPerpVec = vec2(-lOriginToPointOfApp.y, lOriginToPointOfApp.x);
pCircle.torque += TORQUE_MULTIPLIER * dot2(lPerpVec, pForceVector);
}
pCircle.force = addVec2(pCircle.force, pForceVector);
}
function cleanup() {
lPegList.forEach(function(pCircle) { freeCircle(lProgramContext.gl, pCircle); });
freeCircle(lProgramContext.gl, lBall);
lProgramContext.gl.deleteProgram(pProgramInfo.program);
lProgramContext.gl.clearColor(0.0, 0.0, 0.0, 1.0);
lProgramContext.gl.clear(lProgramContext.gl.COLOR_BUFFER_BIT);
}
function reset() {
lExitRequestFunc();
lProgramContext.reset();
$('#time_step_slider').unbind('change');
}
const lExitRequestFunc = requestUpdateLoop(update, cleanup);
lProgramContext.stopButton.on('click', reset);
$('#time_step_slider').on('change', function() { lTimeStepScale = $(this).val(); });
});
}
$(document).ready(main);
})()
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