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I am working with HTML5 with canvas. I already draw a 2D circle.Now i want to shade the circle with a color.but the shading look like a 3D circle.Is this possible with canvas?.Thank you.
Fake smoke and mirrors
To fake a light on a sphere. I am guessing it is a sphere as you say circle and you could mean a donut. This technique will work for a donut as well.
So to lighting.
Phong Shading
The most basic lighting model is Phong (from memory). It uses the angle between the incoming light ray and the surface normal (a line going out from the surface at 90 deg). The amount of reflected light is the cosine of that angle time the light intensity.
Spheres a easy
As the sphere is symmetrical this allows us to use a radial gradient to apply the value for each pixel on the sphere and for a sphere with the light directly overhead this produces a perfect phong shaded sphere with very little effort.
The code that does that. x,y are the center of the sphere and r is the radius. The angle between the light and the surface normal is easy to calculate as you move out from the center of the sphere. It starts at zero and ends at Math.PI/2 (90deg). So the reflected value is the cosine of that angle.
var grd = ctx.createRadialGradient(x,y,0,x,y,r);
var step = (Math.PI/2)/r;
for(var i = 0; i < (Math.PI/2); i += step){
var c = "" + Math.floor(Math.max(0,255 * Math.abs(Math.cos(i)));
grd.addColorStop(i/(Math.PI/2),"rgba("+c+","+c+","+c+","1)");
}
That code creates a gradient to fit the circle.
Mod for Homer food
To do for a donut you need to modify i. The donut has an inner and outer radius (r1, r2) so inside the for loop modify i
var ii = (i/(Math.PI/2)); // normalise i
ii *= r2; // scale to outer edge
ii = ((r1+r2)/2)-ii; // get distance from center line
ii = ii / ((r2-r1)/2); // normalise to half the width;
ii = ii * Math.PI * (1/2); // scale to get the surface norm on the donut.
// use ii as the surface normal to calculate refelected light
var c = "" + Math.floor(Math.max(0,255 * Math.abs(Math.cos(ii)));
Phong Shading Sucks
By phong shading sucks big time and will not do. This also does not allow for lights that are off center or even partly behind the sphere.
We need to add the ability for off centered light. Luck has it that the radial gradients can be offset
var grd = ctx.createRadialGradient(x,y,0,x,y,r);
The first 3 numbers are the start circle of the gradient and can be positioned anywhere. The problem is that when we move the start location the phong shading model falls apart. To fix that there is a little smoke and mirrors stuff that can make the eye believe what the brain wants.
We adjust the fall off, the brightness, the spread, and the angle for each colour stop on the radial gradient depending on how far the light is from the center.
Specular highlights
This improves it a bit but still not the best. Another important component of lighting is specular reflections (the highlight). This is dependent on the angle between the reflected light and the eye. As we do not want to do all that (javascript is slow) we will cludge it via a slight modification of the phong shading. We simply multiply the surface normal by a value greater than 1. Though not perfect it works well.
Surface properties and environment
Next light is coloured, the sphere has reflective qualities that depend on frequency and there is ambient light as well. We don't want to model all this stuff so we need a way to fake it.
This can be done via compositing (Used for almost all 3D movie production). We build up the lighting one layer at a time. The 2D API provides compositing operations for us so we can create several gradients and layer them.
There is a lot more math involved but I have tried to keep it as simple as possible.
A demo
The following demo does a real time shading of a sphere (will work on all radially symmetrical objects) Apart from some setup code for canvas and mouse the demo has two parts the main loop does the compositing by layering the lights and the function createGradient creates the gradient.
The lights used can be found in the object lights and have various properties to control the layer. The first layer should use comp = source-in and lum = 1 or you will end up with the background showing through. All other layer lights can be what every you want.
The flag spec tells the shader that the light is specular and must include the specPower > 1 as I do not vet its existence.
The colours of the light is in the array col and represent Red, green and blue. The values can be greater the 256 and less than 0 as light in the natural world has a huge dynamic range and some effect need you to ramp up the incoming light way above the 255 limit of the RGB pixel.
I add a final "multiply" to the layered result. This is the magic touch in the smoke and mirror method.
If you like the code play with the values and layers. Move the mouse to change the light source location.
This is not real lighting it is fake, but who cares as long as it looks OK. lol
UPDATE
Found a bug so fixed it and while I was here, changed the code to randomize the lights when you click the left mouse button. This is so you can see the range of lighting that can be achieved when using the ctx.globalCompositeOperation in combination with gradients.
var demo = function(){
/** fullScreenCanvas.js begin **/
var canvas = (function(){
var canvas = document.getElementById("canv");
if(canvas !== null){
document.body.removeChild(canvas);
}
// creates a blank image with 2d context
canvas = document.createElement("canvas");
canvas.id = "canv";
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
canvas.style.position = "absolute";
canvas.style.top = "0px";
canvas.style.left = "0px";
canvas.style.zIndex = 1000;
canvas.ctx = canvas.getContext("2d");
document.body.appendChild(canvas);
return canvas;
})();
var ctx = canvas.ctx;
/** fullScreenCanvas.js end **/
/** MouseFull.js begin **/
if(typeof mouse !== "undefined"){ // if the mouse exists
if( mouse.removeMouse !== undefined){
mouse.removeMouse(); // remove prviouse events
}
}else{
var mouse;
}
var canvasMouseCallBack = undefined; // if needed
mouse = (function(){
var mouse = {
x : 0, y : 0, w : 0, alt : false, shift : false, ctrl : false,
interfaceId : 0, buttonLastRaw : 0, buttonRaw : 0,
over : false, // mouse is over the element
bm : [1, 2, 4, 6, 5, 3], // masks for setting and clearing button raw bits;
getInterfaceId : function () { return this.interfaceId++; }, // For UI functions
startMouse:undefined,
mouseEvents : "mousemove,mousedown,mouseup,mouseout,mouseover,mousewheel,DOMMouseScroll".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; }
m.alt = e.altKey;m.shift = e.shiftKey;m.ctrl = e.ctrlKey;
if (t === "mousedown") { m.buttonRaw |= m.bm[e.which-1];
} else if (t === "mouseup") { m.buttonRaw &= m.bm[e.which + 2];
} else if (t === "mouseout") { m.buttonRaw = 0; m.over = false;
} else if (t === "mouseover") { m.over = true;
} else if (t === "mousewheel") { m.w = e.wheelDelta;
} else if (t === "DOMMouseScroll") { m.w = -e.detail;}
if (canvasMouseCallBack) { canvasMouseCallBack(mouse); }
e.preventDefault();
}
function startMouse(element){
if(element === undefined){
element = document;
}
mouse.element = element;
mouse.mouseEvents.forEach(
function(n){
element.addEventListener(n, mouseMove);
}
);
element.addEventListener("contextmenu", function (e) {e.preventDefault();}, false);
}
mouse.removeMouse = function(){
if(mouse.element !== undefined){
mouse.mouseEvents.forEach(
function(n){
mouse.element.removeEventListener(n, mouseMove);
}
);
canvasMouseCallBack = undefined;
}
}
mouse.mouseStart = startMouse;
return mouse;
})();
if(typeof canvas !== "undefined"){
mouse.mouseStart(canvas);
}else{
mouse.mouseStart();
}
/** MouseFull.js end **/
// draws the circle
function drawCircle(c){
ctx.beginPath();
ctx.arc(c.x,c.y,c.r,0,Math.PI*2);
ctx.fill();
}
function drawCircle1(c){
ctx.beginPath();
var x = c.x;
var y = c.y;
var r = c.r * 0.95;
ctx.moveTo(x,y - r);
ctx.quadraticCurveTo(x + r * 0.8, y - r , x + r *1, y - r / 10);
ctx.quadraticCurveTo(x + r , y + r/3 , x , y + r/3);
ctx.quadraticCurveTo(x - r , y + r/3 , x - r , y - r /10 );
ctx.quadraticCurveTo(x - r * 0.8, y - r , x , y- r );
ctx.fill();
}
function drawShadowShadow(circle,light){
var x = light.x; // get the light position as we will modify it
var y = light.y;
var r = circle.r * 1.1;
var vX = x - circle.x; // get the vector to the light source
var vY = y - circle.y;
var dist = -Math.sqrt(vX*vX+vY*vY)*0.3;
var dir = Math.atan2(vY,vX);
lx = Math.cos(dir) * dist + circle.x; // light canb not go past radius
ly = Math.sin(dir) * dist + circle.y;
var grd = ctx.createRadialGradient(lx,ly,r * 1/4 ,lx,ly,r);
grd.addColorStop(0,"rgba(0,0,0,1)");
grd.addColorStop(1,"rgba(0,0,0,0)");
ctx.fillStyle = grd;
drawCircle({x:lx,y:ly,r:r})
}
// 2D light simulation. This is just an approximation and does not match real world stuff
// based on Phong shading.
// x,y,r descript the imagined sphere
// light is the light source
// ambient is the ambient lighting
// amount is the amount of this layers effect has on the finnal result
function createGradient(circle,light,ambient,amount){
var r,g,b; // colour channels
var x = circle.x; // get lazy coder values
var y = circle.y;
var r = circle.r;
var lx = light.x; // get the light position as we will modify it
var ly = light.y;
var vX = light.x - x; // get the vector to the light source
var vY = light.y - y;
// get the distance to the light source
var dist = Math.sqrt(vX*vX+vY*vY);
// id the light is a specular source then move it to half its position away
dist *= light.spec ? 0.5 : 1;
// get the direction of the light source.
var dir = Math.atan2(vY,vX);
// fix light position
lx = Math.cos(dir)*dist+x; // light canb not go past radius
ly = Math.sin(dir)*dist+y;
// add some dimming so that the light does not wash out.
dim = 1 - Math.min(1,(dist / (r*4)));
// add a bit of pretend rotation on the z axis. This will bring in a little backlighting
var lightRotate = (1-dim) * (Math.PI/2);
// spread the light a bit when near the edges. Reduce a bit for spec light
var spread = Math.sin(lightRotate) * r * (light.spec ? 0.5 : 1);
// create a gradient
var grd = ctx.createRadialGradient(lx,ly,spread,x,y,r + dist);
// use the radius to workout what step will cover a pixel (approx)
var step = (Math.PI/2)/r;
// for each pixel going out on the radius add the caclualte light value
for(var i = 0; i < (Math.PI/2); i += step){
if(light.spec){
// fake spec light reduces dim fall off
// light reflected has sharper falloff
// do not include back light via Math.abs
r = Math.max(0,light.col[0] * Math.cos((i + lightRotate)*light.specPower) * 1-(dim * (1/3)) );
g = Math.max(0,light.col[1] * Math.cos((i + lightRotate)*light.specPower) * 1-(dim * (1/3)) );
b = Math.max(0,light.col[2] * Math.cos((i + lightRotate)*light.specPower) * 1-(dim * (1/3)) );
}else{
// light value is the source lum * the cos of the angle to the light
// Using the abs value of the refelected light to give fake back light.
// add a bit of rotation with (lightRotate)
// dim to stop washing out
// then clamp so does not go below zero
r = Math.max(0,light.col[0] * Math.abs(Math.cos(i + lightRotate)) * dim );
g = Math.max(0,light.col[1] * Math.abs(Math.cos(i + lightRotate)) * dim );
b = Math.max(0,light.col[2] * Math.abs(Math.cos(i + lightRotate)) * dim );
}
// add ambient light
if(light.useAmbient){
r += ambient[0];
g += ambient[1];
b += ambient[2];
}
// add the colour stop with the amount of the effect we want.
grd.addColorStop(i/(Math.PI/2),"rgba("+Math.floor(r)+","+Math.floor(g)+","+Math.floor(b)+","+amount+")");
}
//return the gradient;
return grd;
}
// define the circles
var circles = [
{
x: canvas.width * (1/2),
y: canvas.height * (1/2),
r: canvas.width * (1/8),
}
]
function R(val){
return val * Math.random();
}
var lights;
function getLights(){
return {
ambient : [10,30,50],
sources : [
{
x: 0, // position of light
y: 0,
col : [R(255),R(255),R(255)], // RGB intensities can be any value
lum : 1, // total lumanance for this light
comp : "source-over", // composite opperation
spec : false, // if true then use a pretend specular falloff
draw : drawCircle,
useAmbient : true,
},{ // this light is for a little accent and is at 180 degree from the light
x: 0,
y: 0,
col : [R(255),R(255),R(255)],
lum : R(1),
comp : "lighter",
spec : true, // if true then you MUST inclue spec power
specPower : R(3.2),
draw : drawCircle,
useAmbient : false,
},{
x: canvas.width,
y: canvas.height,
col : [R(1255),R(1255),R(1255)],
lum : R(0.5),
comp : "lighter",
spec : false,
draw : drawCircle,
useAmbient : false,
},{
x: canvas.width/2,
y: canvas.height/2 + canvas.width /4,
col : [R(155),R(155),R(155)],
lum : R(1),
comp : "lighter",
spec : true, // if true then you MUST inclue spec power
specPower : 2.32,
draw : drawCircle,
useAmbient : false,
},{
x: canvas.width/3,
y: canvas.height/3,
col : [R(1255),R(1255),R(1255)],
lum : R(0.2),
comp : "multiply",
spec : false,
draw : drawCircle,
useAmbient : false,
},{
x: canvas.width/2,
y: -100,
col : [R(2255),R(2555),R(2255)],
lum : R(0.3),
comp : "lighter",
spec : false,
draw : drawCircle1,
useAmbient : false,
}
]
}
}
lights = getLights();
/** FrameUpdate.js begin **/
var w = canvas.width;
var h = canvas.height;
var cw = w / 2;
var ch = h / 2;
ctx.font = "20px Arial";
ctx.textAlign = "center";
function update(){
ctx.setTransform(1,0,0,1,0,0);
ctx.fillStyle = "#A74"
ctx.fillRect(0,0,w,h);
ctx.fillStyle = "black";
ctx.fillText("Left click to change lights", canvas.width / 2, 20)
// set the moving light source to that of the mouse
if(mouse.buttonRaw === 1){
mouse.buttonRaw = 0;
lights = getLights();
}
lights.sources[0].x = mouse.x;
lights.sources[0].y = mouse.y;
if(lights.sources.length > 1){
lights.sources[1].x = mouse.x;
lights.sources[1].y = mouse.y;
}
drawShadowShadow(circles[0],lights.sources[0])
//do each sphere
for(var i = 0; i < circles.length; i ++){
// for each sphere do the each light
var cir = circles[i];
for(var j = 0; j < lights.sources.length; j ++){
var light = lights.sources[j];
ctx.fillStyle = createGradient(cir,light,lights.ambient,light.lum);
ctx.globalCompositeOperation = light.comp;
light.draw(circles[i]);
}
}
ctx.globalCompositeOperation = "source-over";
if(!STOP && (mouse.buttonRaw & 4)!== 4){
requestAnimationFrame(update);
}else{
if(typeof log === "function" ){
log("DONE!")
}
STOP = false;
var can = document.getElementById("canv");
if(can !== null){
document.body.removeChild(can);
}
}
}
if(typeof clearLog === "function" ){
clearLog();
}
update();
}
var STOP = false; // flag to tell demo app to stop
function resizeEvent(){
var waitForStopped = function(){
if(!STOP){ // wait for stop to return to false
demo();
return;
}
setTimeout(waitForStopped,200);
}
STOP = true;
setTimeout(waitForStopped,100);
}
window.addEventListener("resize",resizeEvent);
demo();
/** FrameUpdate.js end **/
As #danday74 says, you can use a gradient to add depth to your circle.
You can also use shadowing to add depth to your circle.
Here's a proof-of-concept illustrating a 3d donut:
I leave it to you to design your desired circle
var canvas=document.getElementById("canvas");
var ctx=canvas.getContext("2d");
var PI=Math.PI;
drawShadow(150,150,120,50);
function drawShadow(cx,cy,r,strokewidth){
ctx.save();
ctx.strokeStyle='white';
ctx.lineWidth=5;
ctx.shadowColor='black';
ctx.shadowBlur=15;
//
ctx.beginPath();
ctx.arc(cx,cy,r-5,0,PI*2);
ctx.clip();
//
ctx.beginPath();
ctx.arc(cx,cy,r,0,PI*2);
ctx.stroke();
//
ctx.beginPath();
ctx.arc(cx,cy,r-strokewidth,0,PI*2);
ctx.stroke();
ctx.shadowColor='rgba(0,0,0,0)';
//
ctx.beginPath();
ctx.arc(cx,cy,r-strokewidth,0,PI*2);
ctx.fillStyle='white'
ctx.fill();
//
ctx.restore();
}
body{ background-color: white; }
canvas{border:1px solid red; margin:0 auto; }
<canvas id="canvas" width=300 height=300></canvas>
Various thoughts which you can investigate ...
1 use an image as the texture for the circle
2 use a gradient to fill the circle, probably a radial gradient
3 consider using an image mask, a black / white mask which defines transparency ( prob not the right solution here )
I'm converting a Flash application to HTML5 Canvas. Most of the development is finished but for handling the colors there is a code like this in the flash application:
matrix = new Matrix ();
matrix.createGradientBox (600, ColorHeight * 1200, 0, 80, ColorHeight * -600);
Animation_gradient_mc.clear ();
Animation_gradient_mc.beginGradientFill (fillType, colors, alphas, ratios, matrix, spreadMethod, interpolationMethod, focalPointRatio);
The declaration for a radial gradient in CreateJS is the following:
beginRadialGradientFill(colors, ratios, x0, y0, r0, x1, y1, r1 )
Does anyone know a method to apply a Matrix to a gradient fill?
Any help would be appreciated.
Thanks in advance
Edit
Here are some examples of the gradient I'm trying to reproduce:
As you can see it starts off as a standard radial gradient.
However, it can also appear stretched, I think this is where the matrix helps.
I've attempted to create the same effect by creating a createjs.Graphics.Fill with a matrix but it doesn't seem to be doing anything:
var matrix = new VacpMatrix();
matrix.createGradientBox(
600,
discharge_gradient.color_height * 1200,
0,
80,
discharge_gradient.color_height * -600
);
// test_graphics.append(new createjs.Graphics.Fill('#0000ff', matrix));
console.log('matrix', matrix);
test_graphics.append(new createjs.Graphics.Fill('#ff0000', matrix).radialGradient(
discharge_gradient.colors,
discharge_gradient.ratios,
discharge_gradient.x0,
discharge_gradient.y0,
discharge_gradient.r0,
discharge_gradient.x1,
discharge_gradient.y1,
discharge_gradient.r1
));
var discharge_shape = new createjs.Shape(test_graphics);
I extended the Matrix2d class to add a createGradientBox method using code from the openfl project:
p.createGradientBox = function (width, height, rotation, tx, ty) {
if (_.isUndefined(rotation) || _.isNull(rotation)) {
rotation = 0;
}
if (_.isUndefined(tx) || _.isNull(tx)) {
tx = 0;
}
if (_.isUndefined(ty) || _.isNull(ty)) {
ty = 0;
}
var a = width / 1638.4,
d = height / 1638.4;
// Rotation is clockwise
if (rotation != 0) {
var cos = math.cos(rotation),
sin = math.sin(rotation);
this.b = sin * d;
this.c = -sin * a;
this.a = a * cos;
this.d = d * cos;
} else {
this.b = 0;
this.c = 0;
}
this.tx = tx + width / 2;
this.ty = ty + height / 2;
}
I hope the extra information is useful.
I don't know createJS enough, nor Flash Matrix object, but to make this kind of ovalGradient with the native Canvas2d API, you will need to transform the context's matrix.
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var horizontalScale = .3;
var verticalScale = 1;
var gradient = ctx.createRadialGradient(100/horizontalScale, 100/verticalScale, 100, 100/horizontalScale,100/verticalScale,0);
gradient.addColorStop(0,"green");
gradient.addColorStop(1,"red");
// shrink the context's matrix
ctx.scale(horizontalScale, verticalScale)
// draw your gradient
ctx.fillStyle = gradient;
// stretch the rectangle which contains the gradient accordingly
ctx.fillRect(0,0, 200/horizontalScale, 200/verticalScale);
// reset the context's matrix
ctx.setTransform(1,0,0,1,0,0);
canvas{ background-color: ivory;}
<canvas id="canvas" width="200" height="200"></canvas>
So if you are planning to write some kind of a function to reproduce it, have a look at ctx.scale(), ctx.transform() and ctx.setTransform().
EDIT
As you noticed, this will also shrink your drawn shapes, also, you will have to calculate how much you should "unshrink" those at the drawing, just like I did with the fillRect. (agreed, this one was an easy one)
Here is a function that could help you with more complicated shapes. I didn't really tested it (only with the given example), so it may fail somehow, but it can also give you an idea on how to deal with it :
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
function shrinkedRadial(ctx, shapeArray, xScale, yScale, gradientOpts) {
// scaling by 0 is like not drawing
if (!xScale || !yScale) return;
var gO = gradientOpts;
// apply our scale on the gradient options we passed
var gradient = ctx.createRadialGradient(gO.x0 / xScale, gO.y0 / yScale, gO.r0, gO.x1 / xScale, gO.y1 / yScale, gO.r1);
gradient.addColorStop(gO.c1_pos, gO.c1_fill);
gradient.addColorStop(gO.c2_pos, gO.c2_fill);
// shrink the context's matrix
ctx.scale(xScale, yScale);
ctx.fillStyle = gradient;
// execute the drawing operations' string
shapeArray.forEach(function(str) {
var val = str.split(' ');
var op = shapesRef[val[0]];
if (val[1]) {
var pos = val[1].split(',').map(function(v, i) {
// if even, it should be an y axis, otherwise an x one
return i % 2 ? v / yScale : v / xScale;
});
ctx[op].apply(ctx, pos);
} else {
// no parameters
ctx[op]();
}
});
// apply our gradient
ctx.fill();
// reset the transform matrix
ctx.setTransform(1, 0, 0, 1, 0, 0);
}
// just for shortening our shape drawing operations
// notice how arc operations are omitted, it could be implemented but...
var shapesRef = {
b: 'beginPath',
fR: 'fillRect',
m: 'moveTo',
l: 'lineTo',
bC: 'bezierCurveTo',
qC: 'quadraticCurveTo',
r: 'rect',
c: 'closePath'
};
var gradientOpts = {
x0: 232,
y0: 55,
r0: 70,
x1: 232,
y1: 55,
r1: 0,
c1_fill: 'red',
c1_pos: 0,
c2_fill: 'green',
c2_pos: 1
}
var shapes = ['b', 'm 228,133', 'bC 209,121,154,76,183,43', 'bC 199,28,225,34,233,59', 'bC 239,34,270,29,280,39', 'bC 317,76,248,124,230,133']
// our shape is drawn at 150px from the right so we do move the context accordingly, but you won't have to.
ctx.translate(-150, 0);
shrinkedRadial(ctx, shapes, .3, 1, gradientOpts);
ctx.font = '15px sans-serif';
ctx.fillStyle = 'black';
ctx.fillText('shrinked radialGradient', 3, 20);
// how it looks like without scaling :
ctx.translate(50, 0)
var gO = gradientOpts;
var gradient = ctx.createRadialGradient(gO.x0, gO.y0, gO.r0, gO.x1, gO.y1, gO.r1);
gradient.addColorStop(gO.c1_pos, gO.c1_fill);
gradient.addColorStop(gO.c2_pos, gO.c2_fill);
ctx.fillStyle = gradient;
shapes.forEach(function(str) {
var val = str.split(' ');
var op = shapesRef[val[0]];
if (val[1]) {
var pos = val[1].split(',');
ctx[op].apply(ctx, pos);
} else {
ctx[op]();
}
});
ctx.fill();
ctx.font = '15px sans-serif';
ctx.fillStyle = 'black';
ctx.fillText('normal radialGradient', 160, 20);
<canvas id="canvas" width="400" height="150"></canvas>
A standard matrix would adjust inputs:
Width, angle Horizontal, angle Vertical, Height, pos X, pos Y in that order,
Here you are using gradientBox which is not the usual type of AS3 matrix. Expected input:Width, Height, Rotation, pos X, pos Y
I don't use createJS so I'm gunna guess this (you build on it)...
Your usual beginRadialGradientFill(colors, ratios, x0, y0, r0, x1, y1, r1 )
becomes like below (as though gradientBox matrix is involved):
beginRadialGradientFill(colors, ratios, posX, posY, Rotation, Width, Height, Rotation )
I am learning kineticjs through tutorials provided at http://www.html5canvastutorials.com, things are good and easy to understand but, I am having issue in understanding the getIntersection function that i want to use among different objects while dragging to detect collision / overlapping objects.
As far as I have understood the example the getIntersection function expects a position and checks if its intersecting with any other object or not..
Though I got them but with some issues.
I am unable to accomplish this..
Below is the code that I have tried up to now..
<script>
var stage = new Kinetic.Stage({
container: 'container',
width: 1000,
height: 500,
opacity: 0.5
});
var layer = new Kinetic.Layer();
var previous_position;
var new_position;
var collision = false;
var colors = ['red', 'orange', 'yellow', 'green', 'blue', 'purple'];
var yellowBox = null;
for(var n = 0; n < 6; n++) {
// anonymous function to induce scope
(function() {
var i = n;
if(n < 3){
y = 50;
x = i * 100 + i * 10;
}else{
y = 150;
x = (i - 3) * 100 + (i - 3) * 10 ;
if(n == 3){
x = 0;
}
}
var box = new Kinetic.Rect({
x: x,
y: y,
width: 100,
height: 50,
fill: colors[i],
stroke: 'black',
strokeWidth: 4,
draggable: true,
name: colors[i]
});
box.on('dragstart', function() {
previous_position = {
x: this.attrs.x,
y: this.attrs.y
};
});
box.on('dragend', function() {
if(collision){
//this.setPosition(previous_position);
layer.draw();
collision = false;
}else{
//this.setPosition(new_position);
layer.draw();
}
});
box.on("dragmove", function(evt) {
console.log(layer.children.length);
if(layer.children.length > 1){
console.log('dragging');
new_position = {x: this.attrs.x,
y: this.attrs.y};
// var posBL = {x: this.attrs.x,
// y: this.attrs.height + this.attrs.y};
// var posTR = {x: this.attrs.x + this.attrs.width,
// y: this.attrs.y};
var posBR = {x: this.attrs.x + this.attrs.width,
y: this.attrs.y + this.attrs.height };
var collisionTL = this.getStage().getIntersections(new_position);
// var collisionBL = this.getStage().getIntersections(posBL);
// var collisionTR = this.getStage().getIntersections(posTR);
// var collisionBR = this.getStage().getIntersections(posBR);
console.log(collisionTL);
console.log(collisionTL.shapes);
// if(collisionTL.length > 1 || collisionBL.length > 0 || collisionTR.length > 0 || collisionBR.length > 0){
if(collisionTL.length > 1){
console.log(collisionTL.shapes);
collision = true;
}else{ //if(collisionBR.length > 0){
collision = true;
}
// for(i=0; i < collision.length; i++){
// // console.log(collision[i]._id);
// }
}
});
if(colors[i] === 'yellow') {
yellowBox = box;
}
layer.add(box);
})();
}
stage.add(layer);
</script>
in the dragmove event you guyz can see I get the four corner positions of the dragging box {commented right now} and with this I was able to detect the overlap / collision but it has 2 issues:
1. very slow with only 3 objects in my test
2. if non of the corner points intersect it didn't fire the collision stuff {for this one box can be bigger so it can cover the other entirely}
I would highly apreciate if anyone can please help me accomplish this stuff..
[A] Any object dragging if by any mean overlaps any other object I want it to show collision.
[B] If possible make getIntersection to work on a particular layer group whichever is possible
[C] any other workaround beside kineticJS to accomplish the above task
Regards
Ok, the developer of KineticJS is working on improving the .getIntersections() function... or at least he said he is. But until the function is improved you have to make your own collision detection function. Assuming that your objects are rectangles or can be broken into a series of points you should go with something like this:
Create a function which determines if a point is in a shape (if the corner of a rectangle is inside another rectangle) like so:
function checkCollide(pointX, pointY, objectx, objecty, objectw, objecth) { // pointX, pointY belong to one rectangle, while the object variables belong to another rectangle
var oTop = objecty;
var oLeft = objectx;
var oRight = objectx+objectw;
var oBottom = objecty+objecth;
if(pointX > oLeft && pointX < oRight){
if(pointY > oTop && pointY < oBottom ){
return 1;
}
}
else
return 0;
};
then you can do a big loop which iterates through all objects in a layer to check collision, like so:
var children = layer.getChildren();
for( var i=0; i<children.length; i++){ // for each single shape
for( var j=0; j<children.length; j++){ //check each other shape
if(i != j){ //skip if shape is the same
if(checkCollide(children[i].getX(), children[i].getY(), children[j].getX(), children[j].getY(), children[j].getWidth(), children[j].getHeight()))
alert('top left corner collided');
}
}
}
the checkCollide function I provided only checks the collision for the top left corner on each shape, so you have to modify the function to check all corners, it's not a long rewrite, and there are plenty tutorials even here on stackoverflow which deal with 'bounding rectangles collision detection'
This may seem like it is a very heavy function, but surprisingly it is still faster than .getIntersections(). Also, you should throw in extra if statements so that the function doesn't run through all the checks all the time.
I created a game myself and was using .intersects() and was having a lot of slow down. I switched over to this type of 'simpler' collision detection and now my game runs around 60FPS. http://cs.neiu.edu/~tsam/physics/index.phtml (test/test) if you want to check it out. You can view page source to see how I structured the collision detection to be more efficient (such as in checkIntersectsGoal() function.
If I define a canvas and draw few shapes onto it, then how can I pinpoint each of the shape or image so as to declare events and other properties on the each shape. Consider I have a Rectangle and a triangle. SO can I have some mechanism so as to define them as specific entity and can I deal with them individually. I know about KineticJS but I would like to implement this functionality on my own(For learning purpose). Can anyone pinpoint the way to do it. Or may be an algorithmic approach??
I would like explain pinpoint using mouse events
First of all you have to implement a method to get mouse position
function getMousePos(canvas, evt){
// get canvas position
var obj = canvas;
wrapper = document.getElementById('wrapper');
var top = 0;
var left = 0;
while (obj && obj.tagName != 'BODY') {
top += obj.offsetTop;
left += obj.offsetLeft;
obj = obj.offsetParent;
}
// return relative mouse position
var mouseX = evt.clientX - left + window.pageXOffset+wrapper.scrollLeft;
var mouseY = evt.clientY - top + window.pageYOffset+wrapper.scrollTop;
return {
x: mouseX,
y: mouseY
};
}
Rectangle
Say, we have a rectangle with following values x1, y1, w, h
$(canvas).mousemove(function(e){
//Now call the method getMousePos
var mouseX, mouseY;
var mousePos = getMousePos(canvas, e);
mouseX=mousePos.x;
mouseY=mousePos.y;
// check if move on the rect
if(mouseX>x1 && mouseX<x1+w && mouseY>y1 && mouseY<y1+h)
{
alert('mouse on rect')
}
});
Circle
Say, we have a circle with following values x, y, r
$(canvas).mousemove(function(e){
//Now call the method getMousePos
var mouseX, mouseY;
var mousePos = getMousePos(canvas, e);
mouseX=mousePos.x;
mouseY=mousePos.y;
// check if move on the rect
if(Math.pow(mouseX-x,2)+Math.pow(mouseY-y,2)<Math.pow(r,2))
{
alert('mouse on circle')
}
});
By this way we can pinpoint a object of canvas
You can't use any existing functionality in the DOM for that. So you have to write it yourself. You could start by making an object model like this:
function Shape(x, y) {
var obj = {};
obj.x = x;
obj.y = y;
obj.paint = function(canvasTarget) {
}
return obj;
}
function Rectangle(x, y, width, height) {
var obj = Shape(x, y);
obj.width = width;
obj.height = height;
obj.paint = function(canvasTarget) {
//paint rectangle on the canvas
}
return obj;
}
function Canvas(target) {
var obj = {};
obj.target = target
obj.shapes = [];
obj.paint = function() {
//loop through shapes and call paint
}
obj.addShape(shape) {
this.shapes.push(shape);
}
}
After making the object model you could use it to draw the shapes like this:
var cnv = new Canvas();
cnv.addShape(new Rectangle(10,10,100,100));
cnv.paint();
Then you can handle the onclick event on the canvas and determine which shape is clicked on.
I have the following problem: I have this multi-level array (nested array) which contains two rows of bitmapData. Row 1:360 rotated bitmapData objects; row 2: 360 rotated and colored bitmapData objects.
I try to access row 2 but that doesn't work. There are some mysterious error messages coming up ("TypeError: Error #1034: Type Coercion failed: cannot convert []#36d7e9e9 to flash.display.BitmapData. at BasicBlitArrayObject/updateFrame()").
Please can someone help me out with this problem? Thank you very much.
this function rotates and colors bitmapData; the rotated bitmapData is thrown into an array and the colored bitmapData is thrown into another array; a third array is used as a level array for nesting the other two arrays inside of it
public function createColoredRotationBlitArrayFromBD(sourceBitmapData:BitmapData, inc:int, offset:int = 0, color:Number = 1, $alpha:Number = 1):Array
{
tileList = [];
tileListSec = [];
levelArray = [tileList, tileListSec];
var rotation:int = offset;
while (rotation < (360 + offset))
{
var angleInRadians:Number = Math.PI * 2 * (rotation / 360);
var rotationMatrix:Matrix = new Matrix();
rotationMatrix.translate(-sourceBitmapData.width * .5, -sourceBitmapData.height * .5);
rotationMatrix.rotate(angleInRadians);
rotationMatrix.translate(sourceBitmapData.width * .5, sourceBitmapData.height * .5);
var matrixImage:BitmapData = new BitmapData(sourceBitmapData.width, sourceBitmapData.height,
true, 0x00000000);
matrixImage.draw(sourceBitmapData, rotationMatrix);
tileList.push(matrixImage.clone());
bitmapData = new BitmapData(matrixImage.width, matrixImage.height, true, 0x00000000);
bitmapData = matrixImage;
var colorMatrix:ColorMatrixFilter = new ColorMatrixFilter (
[color, 0, 0, 0, 0,
0, 0, 0, 0, 0,
0, 0, 0, 0, 0,
0, 0, 0, $alpha, 0]);
matrixImage.applyFilter(bitmapData, bitmapData.rect, point0, colorMatrix);
tileListSec.push(matrixImage.clone());
rotation += inc;
matrixImage.dispose();
matrixImage = null;
rotationMatrix = null;
bitmapData.dispose();
bitmapData = null;
colorMatrix = null;
}
return(levelArray);
}
creating my rotated and colored bitmapData
animationFrames = tempBlitArrayAsset.createRotationBlitArrayFromBD($bitmapData, 1, 270);
here I try to access the first row of my level array (that doesn't work; I can't access it)
tempEnemy.animationList = animationFrames;
tempEnemy.bitmapData = tempEnemy.animationList[1][tempEnemy.frame];
This function is for updating the frames
public function updateFrame(inc:int, row:int = 0):void
{
frame += inc;
if (frame > animationList.length - 1){
frame = 0;
}
bitmapData = animationList[row][frame];
}
}
this is a line showing how the updateFrame-function is used in my game (trueRotation is 0)
tempEnemy.updateFrame(tempEnemy.trueRotation);
I can't find anything wrong with createColoredRotationBlitArrayFromBD
var $bitmapData:BitmapData = new BitmapData(40,40,false, 0x7f7f7f);
var animationFrames:Array = createColoredRotationBlitArrayFromBD($bitmapData, 1, 270);
trace(animationFrames.length); // 2
trace(animationFrames[0].length); // 360
trace(animationFrames[1].length); // 360
var bitmap:Bitmap = new Bitmap();
this.addChild(bitmap);
bitmap.bitmapData = animationFrames[1][0]; // works..
That seems correct. Right? I get a red tinted bitmap.
The only 'bug' I see in the code you listed is in updateFrame
if (frame > animationList.length - 1){
frame = 0;
}
should probably be:
if (frame > animationList[row].length - 1){
frame = 0;
}
because animationList.length == 2
But everything else looks okay in the code you've provided, so without more code, i'm not sure there is anything to help.