const PI90 = Math.PI / 2;
const PI = Math.PI;
const PI2 = Math.PI * 2;
const INSET = 10; // playfeild inset
const ARROW_SIZE = 6
const SCALE_VEC = 10;
const SCALE_FORCE = 0.15;
const LINE_W = 2;
const LIFE = 12;
const FONT_SIZE = 20;
const FONT = "Arial Black";
const WALL_NORMS = [PI90,PI,-PI90,0]; // dirction of the wall normals
var box = createBox(200, 200, 50, 100);
box.applyForce = applyForce; // Add this function to the box
// render / update function
var mouse = (function(){
function preventDefault(e) { e.preventDefault(); }
var i;
var mouse = {
x : 0, y : 0,buttonRaw : 0,
bm : [1, 2, 4, 6, 5, 3], // masks for setting and clearing button raw bits;
mouseEvents : "mousemove,mousedown,mouseup".split(",")
};
function mouseMove(e) {
var t = e.type, m = mouse;
m.x = e.offsetX; m.y = e.offsetY;
if (m.x === undefined) { m.x = e.clientX; m.y = e.clientY; }
if (t === "mousedown") { m.buttonRaw |= m.bm[e.which-1];
} else if (t === "mouseup") { m.buttonRaw &= m.bm[e.which + 2];}
e.preventDefault();
}
mouse.start = function(element = document){
if(mouse.element !== undefined){ mouse.removeMouse();}
mouse.element = element;
mouse.mouseEvents.forEach(n => { element.addEventListener(n, mouseMove); } );
}
mouse.remove = function(){
if(mouse.element !== undefined){
mouse.mouseEvents.forEach(n => { mouse.element.removeEventListener(n, mouseMove); } );
mouse.element = undefined;
}
}
return mouse;
})();
var canvas,ctx;
function createCanvas(){
canvas = document.createElement("canvas");
canvas.style.position = "absolute";
canvas.style.left = "0px";
canvas.style.top = "0px";
canvas.style.zIndex = 1000;
document.body.appendChild(canvas);
}
function resizeCanvas(){
if(canvas === undefined){
createCanvas();
}
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
ctx = canvas.getContext("2d");
if(box){
box.w = canvas.width * 0.10;
box.h = box.w * 2;
box.mass = box.w * box.h;
}
}
window.addEventListener("resize",resizeCanvas);
resizeCanvas();
mouse.start(canvas)
var tempVecs = [];
function addTempVec(v,vec,col,life = LIFE,scale = SCALE_VEC){tempVecs.push({v:v,vec:vec,col:col,scale:scale,life:life,sLife:life});}
function drawTempVecs(){
for(var i = 0; i < tempVecs.length; i ++ ){
var t = tempVecs[i]; t.life -= 1;
if(t.life <= 0){tempVecs.splice(i, 1); i--; continue}
ctx.globalAlpha = (t.life / t.sLife)*0.25;
drawVec(t.v, t.vec ,t.col, t.scale)
}
}
function drawVec(v,vec,col,scale = SCALE_VEC){
vec = asPolar(vec)
ctx.setTransform(1,0,0,1,v.x,v.y);
var d = vec.dir;
var m = vec.mag;
ctx.rotate(d);
ctx.beginPath();
ctx.lineWidth = LINE_W;
ctx.strokeStyle = col;
ctx.moveTo(0,0);
ctx.lineTo(m * scale,0);
ctx.moveTo(m * scale-ARROW_SIZE,-ARROW_SIZE);
ctx.lineTo(m * scale,0);
ctx.lineTo(m * scale-ARROW_SIZE,ARROW_SIZE);
ctx.stroke();
}
function drawText(text,x,y,font,size,col){
ctx.font = size + "px "+font;
ctx.textAlign = "center";
ctx.textBaseline = "middle";
ctx.setTransform(1,0,0,1,x,y);
ctx.globalAlpha = 1;
ctx.fillStyle = col;
ctx.fillText(text,0,0);
}
function createBox(x,y,w,h){
var box = {
x : x, // pos
y : y,
r : 0.1, // its rotation AKA orientation or direction in radians
h : h, // its height, and I will assume that its depth is always equal to its height
w : w, // its width
dx : 0, // delta x in pixels per frame 1/60th second
dy : 0, // delta y
dr : 0.0, // deltat rotation in radians per frame 1/60th second
getDesc : function(){
var vel = Math.hypot(this.dx ,this.dy);
var radius = Math.hypot(this.w,this.h)/2
var rVel = Math.abs(this.dr * radius);
var str = "V " + (vel*60).toFixed(0) + "pps ";
str += Math.abs(this.dr * 60 * 60).toFixed(0) + "rpm ";
str += "Va " + (rVel*60).toFixed(0) + "pps ";
return str;
},
mass : function(){ return (this.w * this.h * this.h)/1000; }, // mass in K things
draw : function(){
ctx.globalAlpha = 1;
ctx.setTransform(1,0,0,1,this.x,this.y);
ctx.rotate(this.r);
ctx.fillStyle = "#444";
ctx.fillRect(-this.w/2, -this.h/2, this.w, this.h)
ctx.strokeRect(-this.w/2, -this.h/2, this.w, this.h)
},
update :function(){
this.x += this.dx;
this.y += this.dy;
this.dy += 0.061; // alittle gravity
this.r += this.dr;
},
getPoint : function(which){
var dx,dy,x,y,xx,yy,velocityA,velocityT,velocity;
dx = Math.cos(this.r);
dy = Math.sin(this.r);
switch(which){
case 0:
x = -this.w /2;
y = -this.h /2;
break;
case 1:
x = this.w /2;
y = -this.h /2;
break;
case 2:
x = this.w /2;
y = this.h /2;
break;
case 3:
x = -this.w /2;
y = this.h /2;
break;
case 4:
x = this.x;
y = this.y;
}
var xx,yy;
xx = x * dx + y * -dy;
yy = x * dy + y * dx;
var details = asPolar(vector(xx, yy))
xx += this.x;
yy += this.y;
velocityA = polar(details.mag * this.dr, details.dir + PI90);
velocityT = vectorAdd(velocity = vector(this.dx, this.dy), velocityA);
return {
velocity : velocity, // only directional
velocityT : velocityT, // total
velocityA : velocityA, // angular only
pos : vector(xx, yy),
radius : details.mag,
}
},
}
box.mass = box.mass(); // Mass remains the same so just set it with its function
return box;
}
// calculations can result in a negative magnitude though this is valide for some
// calculations this results in the incorrect vector (reversed)
// this simply validates that the polat vector has a positive magnitude
// it does not change the vector just the sign and direction
function validatePolar(vec){
if(isPolar(vec)){
if(vec.mag < 0){
vec.mag = - vec.mag;
vec.dir += PI;
}
}
return vec;
}
// converts a vector from polar to cartesian returning a new one
function polarToCart(pVec, retV = {x : 0, y : 0}){
retV.x = Math.cos(pVec.dir) * pVec.mag;
retV.y = Math.sin(pVec.dir) * pVec.mag;
return retV;
}
// converts a vector from cartesian to polar returning a new one
function cartToPolar(vec, retV = {dir : 0, mag : 0}){
retV.dir = Math.atan2(vec.y,vec.x);
retV.mag = Math.hypot(vec.x,vec.y);
return retV;
}
function polar (mag = 1, dir = 0) { return validatePolar({dir : dir, mag : mag}); } // create a polar vector
function vector (x= 1, y= 0) { return {x: x, y: y}; } // create a cartesian vector
function isPolar (vec) { if(vec.mag !== undefined && vec.dir !== undefined) { return true; } return false; }// returns true if polar
function isCart (vec) { if(vec.x !== undefined && vec.y !== undefined) { return true; } return false; }// returns true if cartesian
// copy and converts an unknown vec to polar if not already
function asPolar(vec){
if(isCart(vec)){ return cartToPolar(vec); }
if(vec.mag < 0){
vec.mag = - vec.mag;
vec.dir += PI;
}
return { dir : vec.dir, mag : vec.mag };
}
// copy and converts an unknown vec to cart if not already
function asCart(vec){
if(isPolar(vec)){ return polarToCart(vec); }
return { x : vec.x, y : vec.y};
}
// normalise makes a vector a unit length and returns it as a cartesian
function normalise(vec){
var vp = asPolar(vec);
vap.mag = 1;
return asCart(vp);
}
function vectorAdd(vec1, vec2){
var v1 = asCart(vec1);
var v2 = asCart(vec2);
return vector(v1.x + v2.x, v1.y + v2.y);
}
// This splits the vector (polar or cartesian) into the components along dir and the tangent to that dir
function vectorComponentsForDir(vec,dir){
var v = asPolar(vec); // as polar
var pheta = v.dir - dir;
var Fv = Math.cos(pheta) * v.mag;
var Fa = Math.sin(pheta) * v.mag;
var d1 = dir;
var d2 = dir + PI90;
if(Fv < 0){
d1 += PI;
Fv = -Fv;
}
if(Fa < 0){
d2 += PI;
Fa = -Fa;
}
return {
along : polar(Fv,d1),
tangent : polar(Fa,d2)
};
}
function doCollision(pointDetails, wallIndex){
var vv = asPolar(pointDetails.velocity); // Cartesian V make sure the velocity is in cartesian form
var va = asPolar(pointDetails.velocityA); // Angular V make sure the velocity is in cartesian form
var vvc = vectorComponentsForDir(vv, WALL_NORMS[wallIndex])
var vac = vectorComponentsForDir(va, WALL_NORMS[wallIndex])
vvc.along.mag *= 1.18; // Elastic collision requiers that the two equal forces from the wall
vac.along.mag *= 1.18; // against the box and the box against the wall be summed.
// As the wall can not move the result is that the force is twice
// the force the box applies to the wall (Yes and currently force is in
// velocity form untill the next line)
vvc.along.mag *= box.mass; // convert to force
//vac.along.mag/= pointDetails.radius
vac.along.mag *= box.mass
vvc.along.dir += PI; // force is in the oppisite direction so turn it 180
vac.along.dir += PI; // force is in the oppisite direction so turn it 180
// split the force into components based on the wall normal. One along the norm the
// other along the wall
vvc.tangent.mag *= 0.18; // add friction along the wall
vac.tangent.mag *= 0.18;
vvc.tangent.mag *= box.mass //
vac.tangent.mag *= box.mass
vvc.tangent.dir += PI; // force is in the oppisite direction so turn it 180
vac.tangent.dir += PI; // force is in the oppisite direction so turn it 180
// apply the force out from the wall
box.applyForce(vvc.along, pointDetails.pos)
// apply the force along the wall
box.applyForce(vvc.tangent, pointDetails.pos)
// apply the force out from the wall
box.applyForce(vac.along, pointDetails.pos)
// apply the force along the wall
box.applyForce(vac.tangent, pointDetails.pos)
//addTempVec(pointDetails.pos, vvc.tangent, "red", LIFE, 10)
//addTempVec(pointDetails.pos, vac.tangent, "red", LIFE, 10)
}
function applyForce(force, loc){ // force is a vector, loc is a coordinate
validatePolar(force); // make sure the force is a valid polar
// addTempVec(loc, force,"White", LIFE, SCALE_FORCE) // show the force
var l = asCart(loc); // make sure the location is in cartesian form
var toCenter = asPolar(vector(this.x - l.x, this.y - l.y));
var pheta = toCenter.dir - force.dir;
var Fv = Math.cos(pheta) * force.mag;
var Fa = Math.sin(pheta) * force.mag;
var accel = asPolar(toCenter); // copy the direction to center
accel.mag = Fv / this.mass; // now use F = m * a in the form a = F/m
var deltaV = asCart(accel); // convert it to cartesian
this.dx += deltaV.x // update the box delta V
this.dy += deltaV.y
var accelA = Fa / (toCenter.mag * this.mass); // for the angular component get the rotation
// acceleration
this.dr += accelA;// now add that to the box delta r
}
// make a box
ctx.globalAlpha = 1;
var lx,ly;
function update(){
// clearLog();
ctx.setTransform(1, 0, 0, 1, 0, 0);
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.setTransform(1, 0, 0, 1, 0, 0);
ctx.lineWidth = 1;
ctx.strokeStyle = "black";
ctx.fillStyle = "#888";
ctx.fillRect(INSET, INSET, canvas.width - INSET * 2, canvas.height - INSET * 2);
ctx.strokeRect(INSET, INSET, canvas.width - INSET * 2, canvas.height - INSET * 2);
ctx.lineWidth = 2;
ctx.strokeStyle = "black";
box.update();
box.draw();
if(mouse.buttonRaw & 1){
var force = asPolar(vector(mouse.x - lx, mouse.y - ly));
force.mag *= box.mass * 0.1;
box.applyForce(force,vector(mouse.x, mouse.y))
addTempVec(vector(mouse.x, mouse.y), asPolar(vector(mouse.x - lx, mouse.y - ly)), "Cyan", LIFE, 5);
}
lx = mouse.x;
ly = mouse.y;
for(i = 0; i < 4; i++){
var p = box.getPoint(i);
// only do one collision per frame or we will end up adding energy
if(p.pos.x < INSET){
box.x += (INSET) - p.pos.x;
doCollision(p,3)
}else
if( p.pos.x > canvas.width-INSET){
box.x += (canvas.width - INSET) - p.pos.x;
doCollision(p,1)
}else
if(p.pos.y < INSET){
box.y += (INSET) -p.pos.y;
doCollision(p,0)
}else
if( p.pos.y > canvas.height-INSET){
box.y += (canvas.height - INSET) -p.pos.y;
doCollision(p,2)
}
drawVec(p.pos,p.velocity,"blue")
}
drawTempVecs();
ctx.globalAlpha = 1;
drawText(box.getDesc(),canvas.width/2,FONT_SIZE,FONT,FONT_SIZE,"black");
drawText("Click drag to apply force to box",canvas.width/2,FONT_SIZE +17,FONT,14,"black");
requestAnimationFrame(update)
}
update();
