How can i move this line vertically animation wise in canvas
ctx.save();
ctx.beginPath();
ctx.fillStyle= "yellow";
ctx.fillRect(30,30,1,100);
ctx.stroke();
ctx.restore();
I am asking because I am trying to make a laser in a game I am creating.
Thanks
You can either use a timer like setInterval or use requestAnimationFrame. Generally when you want to control the frame-rate a simple timer will do. Doing this allows you to have frames, in which then on each frame you update your object's position.
For moving an object have it's x and y position be variables, then have a variable for moving in a direction, such as moveY or velY. You would update your positions by your intended movements each frame. This is done by clearing the canvas then redrawing your object at its new position.
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var xPos = 30;
var yPos = 30
var moveY = 10;
var delay = 100;
var timer = setInterval(function(){
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.save();
ctx.beginPath();
ctx.fillStyle= "yellow";
ctx.fillRect(xPos,yPos,1,100);
ctx.stroke();
ctx.restore();
yPos += moveY;
}, delay);
canvas{ border: 1px solid black; }
<canvas id="canvas" width=500 height=500>
Related
I'm trying to rotate a triangle around a circle, the triangle should always face outwards, meaning it should rotate around the circle, AND around its center I'm guessing.
I found this question, which is something like what I need, but just in reverse.
Another thing I need is to have the triangle pointed at the user's mouse coords. aka the triangle is something like an arrow.
I just edited the code you linked and replaced the rectangle with a triangle, and animate() with a mouse move listener, of course:
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var cx = 100;
var cy = 100;
var radious = 10;
var gap = 5;
var triangleHeight = 25;
var triangleBase = 10;
redraw(cx + 1, cy);
function redraw(mx, my)
{
mox = mx-cx;
moy = my-cy;
rotation = Math.atan2(moy, mox);
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.beginPath();
ctx.arc(cx, cy, radious, 0, Math.PI * 2);
ctx.closePath();
ctx.fill();
ctx.save();
ctx.translate(cx, cy);
ctx.rotate(rotation);
ctx.beginPath();
ctx.moveTo(radious+gap, -triangleBase/2);
ctx.lineTo(radious+gap, triangleBase/2);
ctx.lineTo(radious+gap+triangleHeight, 0);
ctx.lineTo(radious+gap, -triangleBase/2)
ctx.stroke();
ctx.restore();
}
canvas.addEventListener("mousemove", function (e) {
redraw(e.pageX, e.pageY);
}, false);
<canvas id="canvas"></canvas>
BTW, it's my very first piece of code in JS, so, feel free to correct my code if something is funny.
I'm trying to loop my animation, but no matter what I do, it won't loop. I'm pretty new to canvas, javascript and code in general.
var canvas = document.getElementById("fabrication");
var ctx = canvas.getContext("2d");
var background = new Image();
background.src =
"C:/Users/dylan/Desktop/ProjectTwo/Images/fabricationbackground.jpg";
background.onload = function(){
}
//Loading all of my canvas
var posi =[];
posi[1] = 20;
posi[2] = 20;
var dx=10;
var dy=10;
var ballRadius = 4;
//Variables for drawing a ball and it's movement
function drawballleft(){
posi =xy(posi[1],posi[2])
}
function xy(x,y){
ctx.drawImage(background,0,0);
ctx.beginPath();
ctx.arc(x, y, ballRadius, 0, Math.PI*2);
ctx.fillStyle = "#FFFFFFF";
ctx.fill();
ctx.closePath();
var newpos=[];
newpos[1]= x +dx;
newpos[2]= y +dy;
return newpos;
//Drawing the ball, making it move off canvas.
if (newpos[1] > canvas.width) {
newpos[1] = 20;
}
if (newpos[2] > canvas.height) {
newpos[2] = 20;
}
//If statement to detect if the ball moves off the canvas, to make it return to original spot
}
setInterval(drawballleft, 20);
//Looping the function
Please let me know if I've done something wrong, I really want to learn what I'm doing here. The ball is supposed to go off the canvas, and loop back onto itself, but it goes off the canvas and ends.
Thanks in advance!
I have made a few changes to your code.
First I am using requestAnimationFrame instead of setInterval. http://www.javascriptkit.com/javatutors/requestanimationframe.shtml
Second I am not using an image because I didn't want to run into a CORS issue. But you can put your background image back.
I simplified your posi array to use indexes 0 and 1 instead of 1 and 2 to clean up how you create your array.
I moved your return from before the two ifs to after so the ball will move back to the left or top when it goes off the side. I think that was the real problem you were seeing
var canvas = document.getElementById("fabrication");
var ctx = canvas.getContext("2d");
//Loading all of my canvas
var posi =[20,20];
var dx=10;
var dy=10;
var ballRadius = 4;
//Variables for drawing a ball and it's movement
function drawballleft(){
posi = xy(posi[0],posi[1])
requestAnimationFrame(drawballleft);
}
function xy(x,y){
ctx.fillStyle = '#FFF';
ctx.fillRect(0,0,400,300);
ctx.beginPath();
ctx.arc(x, y, ballRadius, 0, Math.PI*2);
ctx.fillStyle = "#000";
ctx.fill();
ctx.closePath();
var newpos=[x+dx,y+dy];
//Drawing the ball, making it move off canvas.
if (newpos[0] > canvas.width) {
newpos[0] = 20;
}
if (newpos[1] > canvas.height) {
newpos[1] = 20;
}
//If statement to detect if the ball moves off the canvas, to make it return to original spot
return newpos;
}
requestAnimationFrame(drawballleft);
canvas {
outline: 1px solid red;
}
<canvas width="400" height="300" id="fabrication"></canvas>
To make it all even simpler...
Use an external script for handling the canvas.
A really good one ;) :
https://github.com/GustavGenberg/handy-front-end#canvasjs
Include it with
<script type="text/javascript" src="https://gustavgenberg.github.io/handy-front-end/Canvas.js"></script>
Then it's this simple:
// Setup canvas
const canvas = new Canvas('my-canvas', 400, 300).start(function (ctx, handyObject, now) {
// init
handyObject.Ball = {};
handyObject.Ball.position = { x: 20, y: 20 };
handyObject.Ball.dx = 10;
handyObject.Ball.dy = 10;
handyObject.Ball.ballRadius = 4;
});
// Update loop, runs before draw loop
canvas.on('update', function (handyObject, delta, now) {
handyObject.Ball.position.x += handyObject.Ball.dx;
handyObject.Ball.position.y += handyObject.Ball.dy;
if(handyObject.Ball.position.x > canvas.width)
handyObject.Ball.position.x = 20;
if(handyObject.Ball.position.y > canvas.height)
handyObject.Ball.position.y = 20;
});
// Draw loop
canvas.on('draw', function (ctx, handyObject, delta, now) {
ctx.clear();
ctx.beginPath();
ctx.arc(handyObject.Ball.position.x, handyObject.Ball.position.y, handyObject.Ball.ballRadius, 0, Math.PI * 2);
ctx.fillStyle = '#000';
ctx.fill();
ctx.closePath();
});
I restructured your code and used the external script, and now it looks much cleaner and easier to read and toubleshoot!
JSFiddle: https://jsfiddle.net/n7osvt7y/
I want to animate an Arc on Canvas, and it works (with a really basic animation, interval), but the outcome is very pixelated/edgy. On the left side I draw an arc (animated), on the right side without animation (smooth).
JsFiddle: http://jsfiddle.net/C8CXz/2/
function degreesToRadians (degrees) {
return degrees * (Math.PI/180);
}
function radiansToDegrees (radians) {
return radians * (180/Math.PI);
}
var canvas = document.getElementById('circle');
var ctx = canvas.getContext('2d');
var start = 0, end = 0;
var int = setInterval(function(){
end++;
ctx.beginPath();
ctx.arc(80, 80, 50, degreesToRadians(0)-Math.PI/2, degreesToRadians(end)-Math.PI/2, false);
ctx.lineWidth = 10;
ctx.stroke();
if(end >= 360) {
clearInterval(int);
}
}, 10);
ctx.beginPath();
ctx.arc(220, 80, 50, degreesToRadians(0)-Math.PI/2, degreesToRadians(360)-Math.PI/2, false);
ctx.lineWidth = 10;
ctx.stroke();
(raw simple code, dont mind the sloppiness)
You need a:
ctx.clearRect(0, 0, w, h);
In each draw loop.
Basically, you are drawing the same arc over itself hundreds of times. The edge pixels that are only partially black are bing darkened over and over until they are completely black.
Things like this are way nearly all canvas animations clear the canvas and draw fresh for each iteration.
Try clearing the drawing rectangle on every frame
ctx.clearRect(x,y,width,height);
http://jsfiddle.net/C8CXz/3/
I found that I first need the clear the canvas.
ctx.clearRect(0, 0, canvas.width, canvas.height);
I have to draw a stroked fill on canvas. For this I call ctx.fill and ctx.stroke separately. Due to this, the shadow of the stroke draws on top of the fill which I want to avoid.
Could somebody please tell if there is a way to avoid this?
Here is my code:
ctx1.fillStyle = "blue";
ctx1.strokeStyle = "black";
ctx1.shadowColor = "rgba(0,255,0, 1)";
ctx1.shadowOffsetX = 50;
ctx1.shadowOffsetY = 50;
ctx1.lineWidth = "20";
ctx.beginPath();
ctx.moveTo(300, 100);
ctx.lineTo(400, 100);
ctx.lineTo(400, 200);
ctx.lineTo(300, 200);
ctx.closePath();
ctx1.fill();
ctx1.stroke();
http://jsfiddle.net/abWYZ/3/
Every time you perform a draw action on the context the shadow is also drawn. The way canvas works is every thing that's drawn is placed on top of what was previously there. So whats happening is the fill is performed, making a shadow of it, and then the stroke is drawn, which makes a shadow on top of all previous drawn objects.
Here is one possible solution.
Live Demo
// Grab the Canvas and Drawing Context
var canvas = document.getElementById('c');
var ctx = canvas.getContext('2d');
ctx.save();
ctx.fillStyle = "blue";
ctx.strokeStyle = "black";
ctx.lineWidth="20";
ctx.beginPath();
ctx.moveTo(300, 100);
ctx.lineTo(400, 100);
ctx.lineTo(400, 200);
ctx.lineTo(300, 200);
ctx.closePath();
ctx.shadowColor = "rgba(0,255,0, 1)";
ctx.shadowOffsetX = 50;
ctx.shadowOffsetY = 50;
ctx.stroke();
ctx.fill();
// clear the shadow
ctx.shadowColor = 0;
ctx.shadowOffsetX = 0;
ctx.shadowOffsetY = 0;
// restroke w/o the shadow
ctx.stroke();
If you use an approach like this I suggest making a function called toggleShadow or something along those lines allowing you to control when the shadows are drawn.
I placed an text on html5 canvas object using fillText option, question is I need to move the text position or change the color of the text that is already rendered.
Shortly I need to know how to Manipulate particular child of canvas element
This will move a small circle over your canvas
var can = document.getElementById('canvas');
can.height = 1000; can.width = 1300;
var ctx = can.getContext('2d');
var x = 10, y = 100;
ctx.fillStyle = "black";
ctx.fillRect(700, 100, 100, 100);
function draw() {
ctx.beginPath();
ctx.arc(x, y, 20, 0, 2 * Math.PI);
ctx.fillStyle = 'rgba(250,0,0,0.4)';
ctx.fill();
x += 2;
ctx.fillStyle = "rgba(34,45,23,0.4)";
ctx.fillRect(0, 0, can.width, can.height);
requestAnimationFrame(draw);
//ctx.clearRect(0,0,can.width,can.height);
}
draw();
<canvas id="canvas" style="background:rgba(34,45,23,0.4)"></canvas>
I think there is no object model behind the canvas, so you cannot access a "child object" like a "text object" and change it.
What you can do is that you draw the text again with a different color that overwrites the "pixels" of the canvas.
If you want to move the text, first you have to either clear the canvas or re-draw the text with a background/transparent color to get rid of the text in the previous position. Then you can draw the text in the new position.
I've never tried it but I think this would be the way to do it.
var canvas = document.getElementById("canvas"); //get the canvas dom object
var ctx = canvas.getContext("2d"); //get the context
var c = { //create an object to draw
x:0, //x value
y:0, //y value
r:5; //radius
}
var redraw = function(){ // this function redraws the c object every frame (FPS)
ctx.clearRect(0, 0, canvas.width, canvas.height); // clear the canvas
ctx.beginPath(); //start the path
ctx.arc(c.x, c.y, c.r, 0, Math.PI*2); //draw the circle
ctx.closePath(); //close the circle path
ctx.fill(); //fill the circle
requestAnimationFrame(redraw);//schedule this function to be run on the next frame
}
function move(){ // this function modifies the object
var decimal = Math.random() // this returns a float between 0.0 and 1.0
c.x = decimal * canvas.width; // mulitple the random decimal by the canvas width and height to get a random pixel in the canvas;
c.y = decimal * canvas.height;
}
redraw(); //start the animation
setInterval(move, 1000); // run the move function every second (1000 milliseconds)
Here is a fiddle for it.
http://jsfiddle.net/r4JPG/2/
If you want easing and translations, change the move method accordingly.
Hope it is allowed to advertise somebody's project.
Take a look at http://ocanvas.org/ you can get inspiration there.
It is object like canvas library. Allows you to handle events, make animations etc.
<html>
<head>
<title>Canvas Exam</title>
</head>
<body>
<canvas id="my_canvas" height="500" width="500" style="border:1px solid black">
</canvas>
<script>
var dom=document.getElementById("my_canvas");
var ctx=dom.getContext("2d");
var x1=setInterval(handler,1);
var x=50;
var y=50;
r=40;
function handler()
{
ctx.clearRect(0,0,500,500);
r1=(Math.PI/180)*0;
r2=(Math.PI/180)*360;
ctx.beginPath();
//x=x*Math.random();
x=x+2;
r=r+10*Math.random();
ctx.arc(x,y,r,r1,r2);
ctx.closePath();
ctx.fillStyle="blue";
ctx.fill();
ctx.stroke();
if(x>400)
{
x=50;
y=y+10;
}
r=40;
}
</script>
</body>
</html>