I am new learner of animation using HTML5 Canvas. I am struggling to create line drawing animation in a canvas with desired length of a line.
Here is the code
var canvas = document.getElementById("canvas"),
context = canvas.getContext("2d"),
width = canvas.width = window.innerWidth,
height = canvas.height = window.innerHeight;
var x = 200;
var y = 200;
draw();
update();
function draw() {
context.beginPath();
context.moveTo(100, 100);
context.lineTo(x, y);
context.stroke();
}
function update() {
context.clearRect(0, 0, width, height);
x = x + 1;
y = y + 1;
draw();
requestAnimationFrame(update);
}
html,
body {
margin: 0px;
}
canvas {
display: block;
}
<canvas id="canvas"></canvas>
The line is growing on Canvas in the above code. But how to achieve that the 200px wide line and animate the movement in x and y direction. And the same animation with multiple lines using for loop and move them in different direction.
Check the reference image ....
Need to move each line in a different direction
Thanks in advance
Find a new reference image which i want to achieve
You need to either use transforms or a bit of trigonometry.
Transforms
For each frame:
Reset transforms and translate to center
Clear canvas
Draw line from center to the right
Rotate x angle
Repeat from step 2 until all lines are drawn
var ctx = c.getContext("2d");
var centerX = c.width>>1;
var centerY = c.height>>1;
var maxLength = Math.min(centerX, centerY); // use the shortest direction for demo
var currentLength = 0; // current length, for animation
var lenStep = 1; // "speed" of animation
function render() {
ctx.setTransform(1,0,0,1, centerX, centerY);
ctx.clearRect(-centerX, -centerY, c.width, c.height);
ctx.beginPath();
for(var angle = 0, step = 0.1; angle < Math.PI * 2; angle += step) {
ctx.moveTo(0, 0);
ctx.lineTo(currentLength, 0);
ctx.rotate(step);
}
ctx.stroke(); // stroke all at once
}
(function loop() {
render();
currentLength += lenStep;
if (currentLength < maxLength) requestAnimationFrame(loop);
})();
<canvas id=c></canvas>
You can use transformation different ways, but since you're learning I kept it simple in the above code.
Trigonometry
You can also calculate the line angles manually using trigonometry. Also here you can use different approaches, ie. if you want to use delta values, vectors or brute force using the math implicit.
For each frame:
Reset transforms and translate to center
Clear canvas
Calculate angle and direction for each line
Draw line
var ctx = c.getContext("2d");
var centerX = c.width>>1;
var centerY = c.height>>1;
var maxLength = Math.min(centerX, centerY); // use the shortest direction for demo
var currentLength = 0; // current length, for animation
var lenStep = 1; // "speed" of animation
ctx.setTransform(1,0,0,1, centerX, centerY);
function render() {
ctx.clearRect(-centerX, -centerY, c.width, c.height);
ctx.beginPath();
for(var angle = 0, step = 0.1; angle < Math.PI * 2; angle += step) {
ctx.moveTo(0, 0);
ctx.lineTo(currentLength * Math.cos(angle), currentLength * Math.sin(angle));
}
ctx.stroke(); // stroke all at once
}
(function loop() {
render();
currentLength += lenStep;
if (currentLength < maxLength) requestAnimationFrame(loop);
})();
<canvas id=c></canvas>
Bonus animation to play around with (using the same basis as above):
var ctx = c.getContext("2d", {alpha: false});
var centerX = c.width>>1;
var centerY = c.height>>1;
ctx.setTransform(1,0,0,1, centerX, centerY);
ctx.lineWidth = 2;
ctx.strokeStyle = "rgba(0,0,0,0.8)";
ctx.shadowBlur = 16;
function render(time) {
ctx.globalAlpha=0.77;
ctx.fillRect(-500, -500, 1000, 1000);
ctx.globalAlpha=1;
ctx.beginPath();
ctx.rotate(0.025);
ctx.shadowColor = "hsl(" + time*0.1 + ",100%,75%)";
ctx.shadowBlur = 16;
for(var angle = 0, step = Math.PI / ((time % 200) + 50); angle < Math.PI * 2; angle += step) {
ctx.moveTo(0, 0);
var len = 150 + 150 * Math.cos(time*0.0001618*angle*Math.tan(time*0.00025)) * Math.sin(time*0.01);
ctx.lineTo(len * Math.cos(angle), len * Math.sin(angle));
}
ctx.stroke();
ctx.globalCompositeOperation = "lighter";
ctx.shadowBlur = 0;
ctx.drawImage(ctx.canvas, -centerX, -centerY);
ctx.drawImage(ctx.canvas, -centerX, -centerY);
ctx.globalCompositeOperation = "source-over";
}
function loop(time) {
render(time);
requestAnimationFrame(loop);
};
requestAnimationFrame(loop);
body {margin:0;background:#222}
<canvas id=c width=640 height=640></canvas>
Here is what I think you are describing...
window.onload = function() {
var canvas = document.getElementById("canvas"),
context = canvas.getContext("2d"),
width = canvas.width = 400,
height = canvas.height = 220,
xcenter = 200,
ycenter = 110,
radius = 0,
radiusmax = 100,
start_angle1 = 0,
start_angle2 = 0;
function toRadians(angle) {
return angle * (Math.PI / 180);
}
function draw(x1, y1, x2, y2) {
context.beginPath();
context.moveTo(x1, y1);
context.lineTo(x2, y2);
context.stroke();
}
function drawWheel(xc, yc, start_angle, count, rad) {
var inc = 360 / count;
for (var angle = start_angle; angle < start_angle + 180; angle += inc) {
var x = Math.cos(toRadians(angle)) * rad;
var y = Math.sin(toRadians(angle)) * rad;
draw(xc - x, yc - y, xc + x, yc + y);
}
}
function update() {
start_angle1 += 0.1;
start_angle2 -= 0.1;
if(radius<radiusmax) radius++;
context.clearRect(0, 0, width, height);
drawWheel(xcenter, ycenter, start_angle1, 40, radius);
drawWheel(xcenter, ycenter, start_angle2, 40, radius);
requestAnimationFrame(update);
}
update();
};
html,
body {
margin: 0px;
}
canvas {
display: block;
}
<canvas id="canvas"></canvas>
This is one that is a variable length emerging pattern. It has a length array element for each spoke in the wheel that grows at a different rate. You can play with the settings to vary the results:
var canvas = document.getElementById("canvas");
var context = canvas.getContext("2d");
var width = canvas.width = window.innerWidth;
var height = canvas.height = window.innerHeight;
var xcenter = width/4;
var ycenter = height/2;
var radius;
var time;
if(width>height) {
radius = height*0.4;
}
else {
radius = width*0.4;
}
var start_angle1 = 0;
var start_angle2 = 0;
function toRadians (angle) {
return angle * (Math.PI / 180);
}
function draw(x1,y1,x2,y2) {
context.beginPath();
context.moveTo(x1,y1);
context.lineTo(x2,y2);
context.stroke();
}
var radmax=width;
var rads = [];
var radsinc = [];
function drawWheel(xc,yc,start_angle,count,rad) {
var inc = 360/count;
var i=0;
for(var angle=start_angle; angle < start_angle+180; angle +=inc) {
var x = Math.cos(toRadians(angle)) * rads[rad+i];
var y = Math.sin(toRadians(angle)) * rads[rad+i];
draw(xc-x,yc-y,xc+x,yc+y);
rads[rad+i] += radsinc[i];
if(rads[rad+i] > radmax) rads[rad+i] = 1;
i++;
}
}
function update() {
var now = new Date().getTime();
var dt = now - (time || now);
time = now;
start_angle1 += (dt/1000) * 10;
start_angle2 -= (dt/1000) * 10;
context.clearRect(0,0,width,height);
drawWheel(xcenter,ycenter,start_angle1,50,0);
drawWheel(xcenter,ycenter,start_angle2,50,50);
requestAnimationFrame(update);
}
function init() {
for(var i=0;i<100;i++) {
rads[i] = 0;
radsinc[i] = Math.random() * 10;
}
}
window.onload = function() {
init();
update();
};
html, body {
margin: 0px;
}
canvas {
width:100%;
height:200px;
display: block;
}
<canvas id="canvas"></canvas>
Related
I'm attempting to draw this shape on screen with canvas.
I have referenced this example which draws a circle: http://jsfiddle.net/loktar/uhVj6/4/ ,but cannot figure it out. Any help would be greatly appreciated. I'm new to canvas.
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius = 75;
var endPercent = 85;
var curPerc = 0;
var counterClockwise = false;
var circ = Math.PI * 2;
var quart = Math.PI / 2;
context.lineWidth = 10;
context.strokeStyle = '#ad2323';
context.shadowOffsetX = 0;
context.shadowOffsetY = 0;
context.shadowBlur = 10;
context.shadowColor = '#656565';
function animate(current) {
context.clearRect(0, 0, canvas.width, canvas.height);
context.beginPath();
context.arc(x, y, radius, -(quart), ((circ) * current) - quart, false);
context.stroke();
curPerc++;
if (curPerc < endPercent) {
requestAnimationFrame(function () {
animate(curPerc / 100)
});
}
}
animate();
I plan on having a bullet point on each angle that would pop up and slightly pause whenever the line gets to that point.
JSFiddle
Intended behavior
Sample values: Velocity: 10; Angle: 45; Color: red; Radius: 50.
On clicking "Shoot!" button, ball should move until it finally disappears behind one of the walls. Note that I want to simulate real world ball with gravity.
Each time we click Shoot, one more ball should be added to the balls array which will also be drawn.
What happens
A black ellipse is shown on clicking shoot once/multiple time. No console errors seen.
Code:
(function () {
var canvas = document.querySelector("canvas"),
ctx = canvas.getContext("2d"),
WIDTH = canvas.width,
HEIGHT = canvas.height;
// our ball object
function Ball(radius, color) {
this.radius = radius;
this.color = color;
this.x = 50; // start coordinates
this.y = 50;
this.velX = 0;
this.velY = 0;
this.accX = 0;
this.accY = 0;
this.gravity = 0;
this.start = function (angle, velocity) {
this.gravity = 9.8;
this.angle = angle / 180 * Math.PI; // convert to radians
this.velX = velocity * Math.cos(this.angle);
this.velY = velocity * Math.sin(this.angle);
this.accX = 0; // zero intially
this.accY = 0; // TODO: set option for user to set himself
};
this.update = function () {
this.velY -= this.gravity;
};
this.draw = function () {
ctx.beginPath();
ctx.arc(this.x, this.y, this.radius, 0, 2 * Math.PI);
ctx.fillSyle = this.color;
ctx.fill();
ctx.closePath();
}
}
// balls array
var balls = [];
document.querySelector("input[type='button']").onclick = function () {
var color = gId("color").value, // getElementById; defined in jsfiddle
velocity = gId("velocity").value,
angle = gId("angle").value,
radius = gId("radius").value;
var ball = new Ball(radius, color);
ball.start(angle, velocity);
balls.push(ball);
};
setInterval(function () {
for (var i = 0, len = balls.length; i < len; i++) {
ctx.clearRect(0, 0, WIDTH, HEIGHT);
balls[i].draw();
balls[i].update();
}
}, 1000 / 60); // 1000/x depicts x fps
I have no idea why it doesn't work. System: Windows 7 on Chrome/Firefox latest.
Any help is appreciated. Please comment for more information.
1) Set width and height attributes on your canvas element instead of applying a css style i.e:
<canvas width="400px" height="400px">You don't support canvas.</canvas>
2) divide the value of gravity by 60 because your update function is invoked every 1/60th of a second i.e:
this.start = function (angle, velocity) {
this.gravity = 9.8 / 60;
this.angle = angle / 180 * Math.PI; // convert to radians
this.velX = velocity * Math.cos(this.angle);
this.velY = velocity * Math.sin(this.angle);
this.accX = 0; // zero intially
this.accY = 0; // TODO: set option for user to set himself
};
3) change the update function to:
this.update = function () {
this.velY += this.gravity;
this.x += this.velX;
this.y += this.velY;
};
4) move the ctx.clearRect method outside the for loop otherwise you will only see one ball animating always i.e
setInterval(function () {
ctx.clearRect(0, 0, WIDTH, HEIGHT);
for (var i = 0, len = balls.length; i < len; i++) {
balls[i].draw();
balls[i].update();
}
}, 1000 / 60); // 1000/x depicts x fps
Here the updated js-fiddle: http://jsfiddle.net/km6ozj6L/1/
I have three arcs, the first one loads on page-load, the second one loads on mouse-over and the third one on mouse-out. I want the mouse-over-out effect to happen each time rather than just one time (as it is now).
here's the fiddle: http://jsfiddle.net/krish7878/7bX7n/
Here's the JS code:
var currentEndAngle = 0;
var currentStartAngle = 0;
var currentEndAngle2 = 0;
var currentStartAngle2 = 0;
var currentEndAngle3 = -0.5;
var currentStartAngle3 = -0.5;
var something = setInterval(draw, 5);
$("#canvas1").hover(
function(){
var something2 = setInterval(draw2, 5);
},
function(){
var something3 = setInterval(draw3, 5);
}
);
function draw() { /***************/
var can = document.getElementById('canvas1'); // GET LE CANVAS
var canvas = document.getElementById("canvas1");
var context = canvas.getContext("2d");
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius;
var width;
var currentColor = "#00b5ff";
var radius = 100;
var width = 8;
var startAngle = currentStartAngle * Math.PI;
var endAngle = (currentEndAngle) * Math.PI;
if(currentEndAngle < 0.1){
currentEndAngle = currentEndAngle - 0.01;
}
if (currentEndAngle < -0.5){
clearInterval(something);
}
context.beginPath();
context.arc(x, y, radius, startAngle, endAngle, true);
context.lineWidth = width;
// line color
context.strokeStyle = currentColor;
context.stroke();
/************************************************/
}
function draw2() { /***************/
var can = document.getElementById('canvas1'); // GET LE CANVAS
var canvas = document.getElementById("canvas1");
var context = canvas.getContext("2d");
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius;
var width;
var currentColor = "#000";
var radius = 100;
var width = 7;
var startAngle = currentStartAngle2 * Math.PI;
var endAngle = (currentEndAngle2) * Math.PI;
if(currentEndAngle2 < 0.1){
currentEndAngle2 = currentEndAngle2 - 0.01;
}
if (currentEndAngle2 < -0.55){
clearInterval(something2);
}
context.beginPath();
context.arc(x, y, radius, startAngle, endAngle, true);
context.lineWidth = width;
// line color
context.strokeStyle = currentColor;
context.stroke();
/*
context.beginPath();
context.clearRect ( 0 , 0 , 400 , 400 );
context.stroke():
/************************************************/
}
function draw3() { /***************/
var can = document.getElementById('canvas1'); // GET LE CANVAS
var canvas = document.getElementById("canvas1");
var context = canvas.getContext("2d");
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius;
var width;
var currentColor = "#00b5ff";
var radius = 100;
var width = 8;
var startAngle = currentStartAngle3 * Math.PI;
var endAngle = (currentEndAngle3) * Math.PI;
if(currentEndAngle3 < 0){
currentEndAngle3 = currentEndAngle3 + 0.01;
}
if (currentEndAngle3 > 0){
clearInterval(something3);
}
context.beginPath();
context.arc(x, y, radius, startAngle, endAngle, false);
context.lineWidth = width;
// line color
context.strokeStyle = currentColor;
context.stroke();
/************************************************/
}
Code Explanation: there are three functions draw(), draw2(), draw3() - draw is run when the page loads, it draws a blue arc, draw2() is executed when mouse-over happens and draws a black line, draw3 is run when mouse-out happens.
Show I draw them on individual canvases and clear them individually or is there a method to get this done?
Here's one way to do it:
A Demo: http://jsfiddle.net/m1erickson/wMy4G/
Define an arc object
var arc={
cx:canvas.width/2,
cy:canvas.height/2,
radius:100,
startRadians:0,
endRadians:-Math.PI/2,
linewidth:8,
animationPercent:0,
animationRate:10,
animationDirection:0,
};
Draw a portion of the arc based on an animation point
function drawArc(arc,color){
var rStart=arc.startRadians;
var rEnd=arc.endRadians;
if(!arc.animationDirection==0){
if(arc.animationDirection>0){
rEnd=arc.animationPercent/100*(rEnd-rStart);
}else{
rEnd=(100-arc.animationPercent)/100*(rEnd-rStart);
}
}
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.beginPath();
ctx.arc(arc.cx,arc.cy,arc.radius,rStart,rEnd,true);
ctx.strokeStyle=color;
ctx.stroke();
}
Animate portions of the arc
function animate(time){
if(continueAnimation){RAF=requestAnimationFrame(animate);}
drawArc(arc,"blue");
arc.animationPercent+=arc.animationRate;
if(arc.animationPercent>=100){
continueAnimation=false;
}
}
React to hover events by drawing or undrawing the arc
$("#canvas").hover(
function(){
cancelAnimationFrame(RAF);
arc.animationPercent=0;
arc.animationDirection=1;
continueAnimation=true;
requestAnimationFrame(animate);
},
function(){
cancelAnimationFrame(RAF);
arc.animationPercent=0;
arc.animationDirection=-1;
continueAnimation=true;
requestAnimationFrame(animate);
}
);
Alright guys, I'm sure this has been asked before, but I couldn't find anything that directly related to what I was doing. So I have these 4 self drawing circles (or gauges.) Each one has it's own value, and I've been looking through just nit picking through codes and books to build this. My question I need to figure out is how I would go about putting in a count up? Basically I want a counter to go from 1 - x (x being the degree of the circle it's in). I've included my js and HTML 5 for you guys to look at.
HTML
<canvas id="a" width="300" height="300"></canvas>
<script>
var canvas = document.getElementById('a');
var context = canvas.getContext('2d');
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius = 75;
var startAngle = 1.5 * Math.PI;
var endAngle = 3.2 * Math.PI;
var counterClockwise = false;
context.beginPath();
context.arc(x, y, radius, startAngle, endAngle, counterClockwise);
context.lineWidth = 15;
// line color
context.strokeStyle = 'black';
context.stroke();
</script>
Canvas.JS
$(document).ready(function(){
function animate(elementId, endPercent) {
var canvas = document.getElementById(elementId);
var context = canvas.getContext('2d');
var x = canvas.width / 2;
var y = canvas.height / 2;
var radius = 75;
var curPerc = 0;
var counterClockwise = false;
var circ = Math.PI * 2;
var quart = Math.PI / 2;
context.lineWidth = 15;
context.strokeStyle = '#85c3b8';
context.shadowOffsetX = 0;
context.shadowOffsetY = 0;
context.shadowBlur = 10;
function render(current) {
context.clearRect(0, 0, canvas.width, canvas.height);
context.beginPath();
context.arc(x, y, radius, -(quart), ((circ) * current) - quart, false);
context.stroke();
curPerc++;
if (curPerc < endPercent) {
requestAnimationFrame(function () {
render(curPerc / 100);
});
}
}
render();
}
$(window).scroll(function(){
if($(this).scrollTop()<1600){
animate('a', 85);
animate('b', 95);
animate('c', 80);
animate('d', 75);
}
});
});
Keep in mind that I am very new to canvas, I appreciate all the help guys!
Demo: http://jsfiddle.net/m1erickson/mYKp5/
You can save your gauges as objects in an array:
var guages=[];
guages.push({ x:50, y:100, radius:40, start:0, end:70, color:"blue" });
guages.push({ x:200, y:100, radius:40, start:0, end:90, color:"green" });
guages.push({ x:50, y:225, radius:40, start:0, end:35, color:"gold" });
guages.push({ x:200, y:225, radius:40, start:0, end:55, color:"purple" });
The render function takes a guage object draws its progress
function render(guage,percent) {
var pct=percent/100;
var extent=parseInt((guage.end-guage.start)*pct);
var current=(guage.end-guage.start)/100*PI2*pct-quart;
ctx.beginPath();
ctx.arc(guage.x,guage.y,guage.radius,-quart,current);
ctx.strokeStyle=guage.color;
ctx.stroke();
ctx.fillStyle=guage.color;
ctx.fillText(extent,guage.x-15,guage.y+5);
}
And the animation loop asks render to draw all gauges from 0-100 percent of their full values
function animate() {
// if the animation is not 100% then request another frame
if(percent<100){
requestAnimationFrame(animate);
}
// redraw all guages with the current percent
drawAll(percent);
// increase percent for the next frame
percent+=1;
}
function drawAll(percent){
// clear the canvas
ctx.clearRect(0, 0, canvas.width, canvas.height);
// draw all the guages
for(var i=0;i<guages.length;i++){
render(guages[i],percent);
}
}
How I can add Html content on a moving element in the Canvas, like this one
http://www.html5canvastutorials.com/labs/html5-canvas-harmonic-oscillator/
where I need to display my link or button on the moving block attached to the spring. Generally for static canvas elements we can use Z-index or overlapping techniques, but these don't work in this case.
Any solutions ?
Check if the following script works:
<script src="http://www.html5canvastutorials.com/libraries/kinetic2d-v1.0.3.js">
</script>
<script>
var button = {
x: 0,
y: 0,
size: 16,
width: 0,
height: 0,
padding: 4,
hover: false,
text: "Click Me",
onclick: function (e) {
// put your event handler code here
}
};
function drawSpring(canvas, context){
context.beginPath();
context.moveTo(0, 0);
for (var y = 0; y < 200; y++) {
// Sine wave equation
var x = 30 * Math.sin(y / 9.05);
context.lineTo(x, y);
}
}
function drawWeight(canvas, context, y){
var size = 100;
context.save();
context.fillStyle = "red";
context.fillRect(-size / 2, 0, size, size);
context.restore();
canvas.fillText(button.text, 0, 0);
button.x = ((canvas.width - button.width) / 2) - button.padding;
button.y = (y + (size - button.height) / 2) - button.padding;
}
window.onload = function(){
var kin = new Kinetic_2d("myCanvas");
var canvas = kin.getCanvas();
var context = kin.getContext();
context.font = button.size + "px Verdana";
context.textAlign = "center";
context.textBaseline = "top";
button.width = 2 * button.padding + context.measureText(button.text);
button.height = 2 * button.padding + button.size;
var theta = 0;
var curleft = 0;
var curtop = 0;
var obj = canvas;
do {
curleft += object.offsetLeft;
curtop += object.offsetTop;
} while (obj = obj.offsetParent);
canvas.addEventListener("mousemove", function (e) {
context.beginPath();
context.rect(button.x, button.y, button.width, button.height);
button.hover = context.isPointInPath(e.pageX - curleft, e.pageY - curtop);
}, false);
canvas.addEventListener("click", function (e) {
if (button.hover) button.onclick(e);
}, false);
kin.setDrawStage(function(){
theta += this.getTimeInterval() / 400;
var scale = 0.8 * (Math.sin(theta) + 1.3);
this.clear();
context.save();
context.translate(canvas.width / 2, 0);
context.save();
context.scale(1, scale);
drawSpring(canvas, context);
context.restore();
context.lineWidth = 6;
context.strokeStyle = "#0096FF"; // blue-ish color
context.stroke();
context.translate(0, 200 * scale);
drawWeight(canvas, context, 200 * scale);
context.restore();
});
kin.startAnimation();
};
</script>