@timohausmann/quadtree-js
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Another quadtree implementation for javascript
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<title>quadtree-js Many-to-many Demo</title>
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<h1><a href="https://github.com/timohausmann/quadtree-js">quadtree-js</a> <small>many-to-many example</small></h1>
<nav class="nav">
<strong>Demos:</strong>
<a href="simple.html">simple</a>
<a href="dynamic.html">dynamic</a>
<span>many to many</span>
<a href="test-retrieve.html">benchmark</a>
</nav>
<div id="canvasContainer">
<canvas id="canvas" width="640" height="480"></canvas>
</div>
<div class="ctrl">
<div class="ctrl-left">
Total Objects: <span id="cnt_total">0</span>
</div>
<div class="ctrl-right">
Total candidates: <span id="cnt_cand">0</span> (avg. per object: <span id="cnt_perc">0</span>)<br />
FPS: <span id="cnt_fps">0</span>
</div>
</div>
<p>
This example shows how Quadtrees can be used for many-to-many checks. All objects can collide with each other.
Two loops are neccessary to first insert all objects into the tree <code>[2]</code> and then check each object for collisions <code>[3]</code>.
</p>
<pre><code class="language-javascript">var myTree = new Quadtree({
x: 0,
y: 0,
width: 640,
height: 480
});
function loop() {
//[1] First, we will clear the quadtree with every game loop.
//This is neccessary to keep the tree clean and accurate
//(due to its recursive nature).
myTree.clear();
//[2] Then we will update the positions of all objects
//and re-insert them into the tree.
for(var i=0;i<myObjects.length;i++) {
myObjects[i].x += myObjects[i].vx;
myObjects[i].y += myObjects[i].vy;
myTree.insert(myObjects[i]);
}
//[3] Now we loop over all objects again …
for(var i=0;i<myObjects.length;i++) {
var myObject = myObjects[i];
//[4] … and retrieve all objects from the same tree node
var candidates = myTree.retrieve(myObject);
//[5] Check all collision candidates
for(k=0;k<candidates.length;k++) {
var myCandidate = candidates[k];
//[6] since all objects are inside the tree,
//we will also retrieve the current object itself.
//That's a collision case we want to skip.
if(myObject === myCandidate) continue;
//[7] check each candidate for real intersection
var intersect = getIntersection(myObject, myCandidate);
//[8] if they actually intersect, we can take further
//actions. In this script, colliding objects will turn
//green and change velocity
if(intersect) {
// … take actions
}
}
}
//[9] finally, draw all objects and the quadtree
drawQuadtree(myTree);
drawObjects();
//request next frame
requestAnimFrame(loop);
}
</pre></code>
<p>
To see the full example code please check the page source or
<a href="https://github.com/timohausmann/quadtree-js/tree/master/docs" target="_blank" rel="noopener noreferrer">visit GitHub</a>.
</p>
<p>
<em>Collision detection is beyond the scope of quadtree-js</em> – this example uses a very
basic collision algorithm that is not bullet-proof and won't fit all cases. Please research a
collision system that will work for you.
</p>
<p>
The collision code in this example is based on
<a href="https://www.metanetsoftware.com/technique/tutorialA.html" target="_blank" rel="noreferrer noopener">
Metanet's N Game Collision Tutorial</a>, which may be a starting point if you are new to collision detection.
There are many great tutorials out there.
</p>
</div>
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<a href="https://github.com/timohausmann/quadtree-js" class="github-corner" aria-label="View source on GitHub"
target="_blank" rel="noopener noreferrer">
<svg width="80" height="80" viewBox="0 0 250 250" aria-hidden="true">
<path d="M0,0 L115,115 L130,115 L142,142 L250,250 L250,0 Z"></path><path d="M128.3,109.0 C113.8,99.7 119.0,89.6 119.0,89.6 C122.0,82.7 120.5,78.6 120.5,78.6 C119.2,72.0 123.4,76.3 123.4,76.3 C127.3,80.9 125.5,87.3 125.5,87.3 C122.9,97.6 130.6,101.9 134.4,103.2" fill="currentColor" style="transform-origin: 130px 106px;" class="octo-arm"></path><path d="M115.0,115.0 C114.9,115.1 118.7,116.5 119.8,115.4 L133.7,101.6 C136.9,99.2 139.9,98.4 142.2,98.6 C133.8,88.0 127.5,74.4 143.8,58.0 C148.5,53.4 154.0,51.2 159.7,51.0 C160.3,49.4 163.2,43.6 171.4,40.1 C171.4,40.1 176.1,42.5 178.8,56.2 C183.1,58.6 187.2,61.8 190.9,65.4 C194.5,69.0 197.7,73.2 200.1,77.6 C213.8,80.2 216.3,84.9 216.3,84.9 C212.7,93.1 206.9,96.0 205.4,96.6 C205.1,102.4 203.0,107.8 198.3,112.5 C181.9,128.9 168.3,122.5 157.7,114.1 C157.9,116.9 156.7,120.9 152.7,124.9 L141.0,136.5 C139.8,137.7 141.6,141.9 141.8,141.8 Z" fill="currentColor" class="octo-body"></path>
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<!-- quadtree lib and script -->
<script src="./quadtree.min.js"></script>
<!-- CDN alternative: -->
<!-- <script src="https://cdn.jsdelivr.net/npm/@timohausmann/quadtree-js/quadtree.min.js"></script> -->
<script>
(function(w) {
w.requestAnimFrame = (function () {
return w.requestAnimationFrame ||
w.webkitRequestAnimationFrame ||
w.mozRequestAnimationFrame ||
w.oRequestAnimationFrame ||
w.msRequestAnimationFrame ||
function (callback) {
w.setTimeout(callback, 1000 / 60);
};
})();
var ctx = document.getElementById('canvas').getContext('2d');
var cnt_total = document.querySelector('#cnt_total'),
cnt_cand = document.querySelector('#cnt_cand'),
cnt_fps = document.querySelector('#cnt_fps'),
cnt_perc = document.querySelector('#cnt_perc');
/*
* the main Quadtree
*/
var myTree = new Quadtree({
x: 0,
y: 0,
width: 640,
height: 480
});
/*
* our objects will be stored here
*/
var myObjects = [];
/*
* create some objects and save them in myObjects
*/
for(var i=0;i<800;i++) {
myObjects.push({
x : randMinMax(0, 640-16),
y : randMinMax(0, 480-16),
width : randMinMax(4, 16),
height : randMinMax(4, 16),
vx: randMinMax(-0.5,0.5),
vy: randMinMax(-0.5,0.5),
check : false
});
}
cnt_total.innerHTML = myObjects.length;
/*
* draw Quadtree nodes
*/
var drawQuadtree = function(node) {
var bounds = node.bounds;
//no subnodes? draw the current node
if(node.nodes.length === 0) {
ctx.strokeStyle = 'rgba(255,0,0,0.25)';
ctx.strokeRect(bounds.x, bounds.y, bounds.width, bounds.height);
//has subnodes? drawQuadtree them!
} else {
for(var i=0;i<node.nodes.length;i++) {
drawQuadtree(node.nodes[i]);
}
}
};
/*
* draw all objects
*/
var drawObjects = function() {
var obj;
for(var i=0;i<myObjects.length;i++) {
obj = myObjects[i];
if(obj.check) {
ctx.strokeStyle = 'rgba(48,255,48,0.5)';
} else {
ctx.strokeStyle = 'rgba(255,255,255,0.5)';
}
ctx.strokeRect(obj.x, obj.y, obj.width, obj.height);
}
};
/*
* our main loop
*/
var lastLoop = new Date();
var loop = function() {
//calculate FPS
var thisLoop = new Date();
var fps = 1000 / (thisLoop - lastLoop);
lastLoop = thisLoop;
cnt_fps.innerHTML = Math.round(fps);
//[1] clear the tree
myTree.clear();
ctx.clearRect(0, 0, 640, 480);
//[2] update myObjects and insert them into the tree again
for(var i=0;i<myObjects.length;i++) {
myObjects[i].x += myObjects[i].vx;
myObjects[i].y += myObjects[i].vy;
myObjects[i].check = false;
//bounce objects when they reach the canvas border
if(myObjects[i].x > 640 - myObjects[i].width ||
myObjects[i].x < 0) myObjects[i].vx *= -1;
if(myObjects[i].y > 480 - myObjects[i].height ||
myObjects[i].y < 0) myObjects[i].vy *= -1;
myTree.insert(myObjects[i]);
}
//[3] now that the tree is filled, we have to check each object for collisions
for(var i=0;i<myObjects.length;i++) {
var myObject = myObjects[i];
//[4] first, get all collision candidates
var candidates = myTree.retrieve(myObject);
//[5] let's check them for actual collision
for(k=0;k<candidates.length;k++) {
var myCandidate = candidates[k];
//[6] don't check objects against themselves
if(myObject === myCandidate) continue;
//[7] get intersection data
var intersect = getIntersection(myObject, myCandidate);
//no intersection - continue
if(intersect === false) continue;
//[8]
myObject.check = true;
myCandidate.check = true;
//Perform X Push
if(intersect.pushX < intersect.pushY) {
if(intersect.dirX < 0) {
myObject.x = myCandidate.x - myObject.width;
} else if(intersect.dirX > 0) {
myObject.x = myCandidate.x + myCandidate.width;
}
//reverse X trajectory (bounce)
myObject.vx *= -1;
//Perform Y Push
} else {
if(intersect.dirY < 0) {
myObject.y = myCandidate.y - myObject.height;
} else if(intersect.dirY > 0) {
myObject.y = myCandidate.y + myCandidate.height;
}
//reverse Y trajectory (bounce)
myObject.vy *= -1;
}
}
}
//[9] draw objects and quadtree
drawQuadtree(myTree);
drawObjects();
//update UI info
var candidates = myObjects.filter(function(e) { return e.check === true; })
updateCandidatesInfo(candidates);
//request next frame
requestAnimFrame(loop);
};
function getIntersection(r1, r2) {
var r1w = r1.width/2,
r1h = r1.height/2,
r2w = r2.width/2,
r2h = r2.height/2;
var distX = (r1.x + r1w) - (r2.x + r2w);
var distY = (r1.y + r1h) - (r2.y + r2h);
if(Math.abs(distX) < r1w + r2w && Math.abs(distY) < r1h + r2h) {
return {
pushX : (r1w + r2w) - Math.abs(distX),
pushY : (r1h + r2h) - Math.abs(distY),
dirX : distX === 0 ? 0 : distX < 0 ? -1 : 1,
dirY : distY === 0 ? 0 : distY < 0 ? -1 : 1
}
} else {
return false;
}
}
var updateCandidatesInfo = function(candidates) {
var avg = myObjects.length/candidates.length;
cnt_cand.innerHTML = candidates.length;
if(!myObjects.length) return;
cnt_perc.innerHTML = Math.round(avg);
}
//init first loop
loop();
/**
* return a random number within given boundaries.
*
* @param {number} min the lowest possible number
* @param {number} max the highest possible number
* @param {boolean} round if true, return integer
* @return {number} a random number
*/
function randMinMax(min, max, round) {
var val = min + (Math.random() * (max - min));
if(round) val = Math.round(val);
return val;
};
})(window);
</script>
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</html>