Develop Reference

Handle mouse hovering image inside of canvas isometric grid

I got a isometric grid in html canvas.
I am trying to handle the mouse hover the buildings.
Some buildings will have different heights.
As you can see in the image below I am hovering a tile, the mouse pointer is inside the blueish tile.
The problem is when the mouse pointer is off the ground tile, or in the middle of the building image, the highlighted tile goes off.
Need a way to click on each individual building, how can this be resolved?
Main basic functions:
let applied_map = ref([]); // tileMap
let tile_images = ref([]); // this will contain loaded IMAGES for canvas to consume from
let tile_height = ref(50);
let tile_width = ref(100);
const renderTiles = (x, y) => {
let tileWidth = tile_width.value;
let tileHeight = tile_height.value;
let tile_half_width = tileWidth / 2;
let tile_half_height = tileHeight / 2;
for (let tileX = 0; tileX < gridSize.value; ++tileX) {
for (let tileY = 0; tileY < gridSize.value; ++tileY) {
let renderX = x + (tileX - tileY) * tile_half_width;
let renderY = y + (tileX + tileY) * tile_half_height;
let tile = applied_map.value[tileY * gridSize.value + tileX];
renderTileBackground(renderX, renderY + 50, tileWidth, tileHeight);
if (tile !== -1) {
if (tile_images.value.length) {
renderTexturedTile(
tile_images.value[tile].img,
renderX,
renderY + 40,
tileHeight
);
}
}
}
}
if (
hoverTileX.value >= 0 &&
hoverTileY.value >= 0 &&
hoverTileX.value < gridSize.value &&
hoverTileY.value < gridSize.value
) {
let renderX = x + (hoverTileX.value - hoverTileY.value) * tile_half_width;
let renderY = y + (hoverTileX.value + hoverTileY.value) * tile_half_height;
renderTileHover(renderX, renderY + 50, tileWidth, tileHeight);
}
};
const renderTileBackground = (x, y, width, height) => {
ctx.value.beginPath();
ctx.value.setLineDash([5, 5]);
ctx.value.strokeStyle = "black";
ctx.value.fillStyle = "rgba(25,34, 44,0.2)";
ctx.value.lineWidth = 1;
ctx.value.moveTo(x, y);
ctx.value.lineTo(x + width / 2, y - height / 2);
ctx.value.lineTo(x + width, y);
ctx.value.lineTo(x + width / 2, y + height / 2);
ctx.value.lineTo(x, y);
ctx.value.stroke();
ctx.value.fill();
};
const renderTexturedTile = (imgSrc, x, y, tileHeight) => {
let offsetY = tileHeight - imgSrc.height;
ctx.value.drawImage(imgSrc, x, y + offsetY);
};
const renderTileHover = (x, y, width, height) => {
ctx.value.beginPath();
ctx.value.setLineDash([]);
ctx.value.strokeStyle = "rgba(161, 153, 255, 0.8)";
ctx.value.fillStyle = "rgba(161, 153, 255, 0.4)";
ctx.value.lineWidth = 2;
ctx.value.moveTo(x, y);
ctx.value.lineTo(x + width / 2, y - height / 2);
ctx.value.lineTo(x + width, y);
ctx.value.lineTo(x + width / 2, y + height / 2);
ctx.value.lineTo(x, y);
ctx.value.stroke();
ctx.value.fill();
};
Updates after answer below
Based on Helder Sepulveda answer I created a function drawCube.
And added to my click function and to the renderTiles. So on click and frame update it creates a cube with 3 faces,and its placed on same position as the building and stores the Path on a global variable, the cube follows the isometric position.
In the drawCube, there is a condition where i need to hide the right face from the cube. Hide if there's a building on the next tile. So if you hover the building it wont trigger the last building on.
//...some code click function
//...
if (tile_images.value[tileIndex] !== undefined) {
drawCube(
hoverTileX.value + tile_height.value,
hoverTileY.value +
Number(tile_images.value[tileIndex].img.height / 2) -
10,
tile_height.value, // grow X pos to left
tile_height.value, // grow X pos to right,
Number(tile_images.value[tileIndex].img.height / 2), // height,
ctx.value,
{
tile_index: tileIndex - 1 < 0 ? 0 : tileIndex - 1,
}
);
}
This is the drawCube
const drawCube = (x, y, wx, wy, h, the_ctx, options = {}) => {
// https://codepen.io/AshKyd/pen/JYXEpL
let path = new Path2D();
let hide_options = {
left_face: false,
right_face: false,
top_face: false,
};
if (options.hasOwnProperty("hide")) {
hide_options = Object.assign(hide_options, options.hide);
}
// left face
if (!hide_options.left_face) {
path.moveTo(x, y);
path.lineTo(x - wx, y - wx * 0.5);
path.lineTo(x - wx, y - h - wx * 0.5);
path.lineTo(x, y - h * 1);
}
// right;
if (
!hide_options.right_face &&
!coliders.value[options.tile_index].hide_right_face
) {
path.moveTo(x, y);
path.lineTo(x + wy, y - wy * 0.5);
path.lineTo(x + wy, y - h - wy * 0.5);
path.lineTo(x, y - h * 1);
}
//top
if (!hide_options.right_face) {
path.moveTo(x, y - h);
path.lineTo(x - wx, y - h - wx * 0.5);
path.lineTo(x - wx + wy, y - h - (wx * 0.5 + wy * 0.5));
path.lineTo(x + wy, y - h - wy * 0.5);
}
// the_ctx.beginPath();
let isONHover = the_ctx.isPointInPath(
path,
mousePosition.x - 10,
mousePosition.y - 10
);
the_ctx.fillStyle = null;
if (isONHover) {
// let indx = options.tile_pos.y * gridSize.value + options.tile_pos.x;
//this is the click on object event
if (isMouseDown.value) {
//Trigger
if (buildozer.value === true) {
coliders.value[options.tile_index] = -1;
applied_map.value[options.tile_index] = -1;
}
isMouseDown.value = false;
}
the_ctx.fillStyle = "green";
}
the_ctx.fill(path);
if (
coliders.value[options.tile_index] == -1 &&
applied_map.value[options.tile_index]
) {
coliders.value[options.tile_index] = path;
}
};

In a nutshell you need to be able to detect mouseover on more complex shapes ...
I recommend you to use Path2d:
https://developer.mozilla.org/en-US/docs/Web/API/Path2D
That way you can build any shape you like and then we have access to isPointInPath to detect if the mouse is over our shape.
https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/isPointInPath
Here is a small example:
class Shape {
constructor(x, y, width, height) {
this.path = new Path2D()
this.path.arc(x, y, 12, 0, 2 * Math.PI)
this.path.arc(x, y - 9, 8, 0, 1.5 * Math.PI)
this.path.lineTo(x + width / 2, y)
this.path.lineTo(x, y + height / 2)
this.path.lineTo(x - width / 2, y)
this.path.lineTo(x, y - height / 2)
this.path.lineTo(x + width / 2, y)
}
draw(ctx, pos) {
ctx.beginPath()
ctx.fillStyle = ctx.isPointInPath(this.path, pos.x, pos.y) ? "red" : "green"
ctx.fill(this.path)
}
}
function getMousePos(canvas, evt) {
var rect = canvas.getBoundingClientRect()
return {
x: evt.clientX - rect.left,
y: evt.clientY - rect.top
}
}
var canvas = document.getElementById("canvas")
var ctx = canvas.getContext("2d")
shapes = []
for (var i = 0; i < 4; i++) {
for (var j = 0; j < 4; j++) {
shapes.push(new Shape(50 + i * 40, 40 + j * 40, 40, 20))
}
}
canvas.addEventListener("mousemove", function(evt) {
ctx.clearRect(0, 0, canvas.width, canvas.height)
var mousePos = getMousePos(canvas, evt)
shapes.forEach((s) => {s.draw(ctx, mousePos)})
},
false
)
shapes.forEach((s) => {
s.draw(ctx, {x: 0, y: 0})
})
<canvas id="canvas" width="200" height="200"></canvas>
This example draws a "complex" shape (two arcs and a few lines) and the shape changes color to red when the mouse is hovering the shape

Weird shape when trying to rendering 3d rotating cube

I'm trying make render 3d rotating cube but cube has weird shape, I can't find the bug/glitch.
I'm following this tutorial on youtube.
I think I made something wrong on my code but everything seems good to me and I checked values on chrome debugging mode.
But when I following the tutorial I make some personal change but i'm sure this changes doesn't effect code working and make optimization on working.
Thanks.
const canvas = document.getElementById('canvas'), ctx = canvas.getContext('2d');
const W = 600, H = 600;
const MODEL_MAX_X = 2, MODEL_MIN_X = -2, MODEL_MAX_Y = 2, MODEL_MIN_Y = -2, STEP = 0.5;
var points = [], triangles = [];
for (let x = -1; x <= 1; x += STEP)
for (let y = -1; y <= 1; y += STEP)
for (let z = -1; z <= 1; z += STEP)
points.push([x, y, z]);
for (let dimension = 0; dimension <= 2; ++dimension)
for (let side = -1; side <= 1; side += 2) {
var sidePoints = points.filter(point => point[dimension] == side).slice(0,3);
triangles.push([...sidePoints]);
}
function persvectiveProjection([x, y, z]) {
return [x / (z + 4), y / (z + 4)];
}
function project(point) {
const [x, y] = persvectiveProjection(point);
return [
W * (x - MODEL_MIN_X) / (MODEL_MAX_X - MODEL_MIN_X),
H * (1 - y - MODEL_MIN_Y) / (MODEL_MAX_Y - MODEL_MIN_Y)
];
}
ctx.lineWidth = 4;
ctx.strokeStyle = '#000';
function renderPoint(point) {
const [x, y] = project(point);
ctx.beginPath();
ctx.moveTo(x, y);
ctx.lineTo(x + 1, y + 1);
ctx.stroke();
}
function renderTriangle (triangle) {
const projectedTriangle = triangle.map(project);
const [a, b, c] = projectedTriangle;
ctx.beginPath();
ctx.moveTo(a[0], a[1]);
ctx.lineTo(b[0], b[1]);
ctx.lineTo(c[0], c[1]);
ctx.lineTo(a[0], a[1]);
ctx.stroke();
}
function rotateY(point, theta) {
const [x, y, z] = point;
return [
Math.cos(theta) * x - Math.sin(theta) * z,
y,
Math.sin(theta) * x + Math.cos(theta) * z
]
}
function rotateX(point, theta) {
const [x, y, z] = point;
return [
x,
Math.cos(theta) * y - Math.sin(theta) * z,
Math.sin(theta) * y + Math.cos(theta) * z
]
}
var theta = 0;
var dtheta = 0.01;
function render() {
ctx.clearRect(0, 0, W, H);
theta += dtheta;
triangles.forEach(triangle => {
var rotatedTriangle = triangle.map(point => rotateX(rotateY(point, theta), 0.43 * theta));
renderTriangle(rotatedTriangle);
})
requestAnimationFrame(render);
}
render();

How to transalate hexagon in canvas html using typescript

i drew a hexagon on canvas in html and i want to tranaslate the hexagon in canvas when i use a translate method it doesn't translate the hexagon but when i translate it does translate when i use the rectangle .
var canvas:HTMLCanvasElement = document.getElementById("myCanvas");
var context:CanvasRenderingContext2D = canvas.getContext("2d");
var x = 300;
var y = 100;
context.beginPath();
context.moveTo(x, y);
x = x + 120;
y = y + 100;
context.lineTo(x, y);
y = y + 120;
context.lineTo(x, y);
x = x - 125;
y = y + 100;
context.lineTo(x, y);
x = x - 125;
y = y - 100;
context.lineTo(x, y);
y = y - 120;
context.lineTo(x, y);
x = x + 130;
y = y - 100;
context.lineTo(x, y);
context.strokeStyle = "red";
context.lineWidth = 4;
context.fillStyle = "blue";
context.fill();
context.translate(400,400);
context.fillStyle = "blue";
context.fill();
context.save();
context.fillRect(10, 10, 100, 50);
context.translate(70, 70);
context.fillRect(10, 10, 100, 50);
Edit 1:
according to the #helder gave the answer I've made the changes but translate is not working
function hexagon(x:number, y:number, r:number, color:string) {
context.beginPath();
var angle = 0
for (var j = 0; j < 6; j++) {
var a = angle * Math.PI / 180
var xd = r * Math.sin(a)
var yd = r * Math.cos(a)
context.lineTo(x + xd, y + yd);
angle += 360 / 6
}
context.fillStyle = color;
context.fill();
context.translate(70,70);
context.fill();
}
hexagon(100, 100, 50, "red")

I would try to create a function that draws the hexagon that way you don't have to use translate.
See below
c = document.getElementById("canvas");
context = c.getContext("2d");
function hexagon(x, y, r, color) {
context.beginPath();
var angle = 0
for (var j = 0; j < 6; j++) {
var a = angle * Math.PI / 180
var xd = r * Math.sin(a)
var yd = r * Math.cos(a)
context.lineTo(x + xd, y + yd);
angle += 360 / 6
}
context.fillStyle = color;
context.fill();
}
hexagon(50, 50, 30, "red")
hexagon(40, 40, 10, "blue")
hexagon(60, 60, 10, "lime")
<canvas id=canvas >
Here is a break down of function hexagon(x, y, r, color)
it takes the center of the hexagon (x,y) a radius (r) and color
we loop over the six vertices and draw lines
the calculations are just a bit of trigonometry nothing fancy
With that we can draw hexagons at any location we want.
and that same function you can easily refactor to draw an octagon or other polygons.
Here is an animated version of those hexagons
c = document.getElementById("canvas");
context = c.getContext("2d");
delta = 0
function hexagon(x, y, r, color) {
context.beginPath();
var angle = 0
for (var j = 0; j < 6; j++) {
var a = angle * Math.PI / 180
var xd = r * Math.sin(a)
var yd = r * Math.cos(a)
context.lineTo(x + xd, y + yd);
angle += 360 / 6
}
context.fillStyle = color;
context.fill();
}
function draw() {
context.clearRect(0, 0, c.width, c.height)
var xd = 10 * Math.sin(delta)
var yd = 10 * Math.cos(delta)
hexagon(50 - xd, 50 - yd, 30, "red")
hexagon(40 + xd, 40 + yd, 10, "blue")
delta += 0.2
}
setInterval(draw, 100);
<canvas id=canvas>
As you can see there is no need to use translate

html canvas check that object is in angle

I have a circle, and a object.
I want to draw a circle segment with specified spread, and next check that the object is in defined angle, if it is, angle color will be red, otherwise green. But my code does not work in some cases...
in this case it work:
in this too:
but here it isn't:
I know that my angle detection code part is not perfect, but I have no idea what I can do.
This is my code:
html:
<html>
<head></head>
<body>
<canvas id="c" width="800" height="480" style="background-color: #DDD"></canvas>
<script src="script.js"></script>
</body>
</html>
js:
window.addEventListener('mousemove', updateMousePos, false);
var canvas = document.getElementById("c");
var context = canvas.getContext("2d");
//mouse coordinates
var mx = 0, my = 0;
draw();
function draw()
{
context.clearRect(0, 0, canvas.width, canvas.height);
//object coordinates
var ox = 350, oy = 260;
context.beginPath();
context.arc(ox,oy,5,0,2*Math.PI);
context.fill();
//circle
var cx = 400, cy = 280;
var r = 100;
var segmentPoints = 20;
var circlePoints = 40;
var spread = Math.PI / 2;
var mouseAngle = Math.atan2(my - cy, mx - cx); //get angle between circle center and mouse position
context.beginPath();
context.strokeStyle = "blue";
context.moveTo(cx + r, cy);
for(var i=0; i<circlePoints; i++)
{
var a = 2 * Math.PI / (circlePoints - 1) * i;
var x = cx + Math.cos(a) * r;
var y = cy + Math.sin(a) * r;
context.lineTo(x, y);
}
context.lineTo(cx + r, cy);
context.stroke();
var objAngle = Math.atan2(oy - cy, ox - cx);
var lowerBorder = mouseAngle - spread / 2;
var biggerBorder = mouseAngle + spread / 2;
/////////////////////////////////////////////ANGLES DETECTION PART
if(objAngle >= lowerBorder && objAngle <= biggerBorder ||
objAngle <= biggerBorder && objAngle >= lowerBorder)
{
context.strokeStyle = "red";
}
else
context.strokeStyle = "green";
context.lineWidth = 3;
//angle center line
context.beginPath();
context.moveTo(cx, cy);
context.lineTo(cx + Math.cos(mouseAngle) * r * 2, cy + Math.sin(mouseAngle) * r * 2);
context.stroke();
//draw spread arc
context.beginPath();
context.moveTo(cx, cy);
for(var i=0; i<segmentPoints; i++)
{
var a = mouseAngle - spread / 2 + spread / (segmentPoints - 1) * i;
var x = cx + Math.cos(a) * r;
var y = cy + Math.sin(a) * r;
context.lineTo(x, y);
}
context.lineTo(cx, cy);
context.stroke();
//show degrees
context.font = "20px Arial";
context.fillText((lowerBorder * 180 / Math.PI).toFixed(2), Math.cos(lowerBorder) * r + cx, Math.sin(lowerBorder) * r + cy);
context.fillText((biggerBorder * 180 / Math.PI).toFixed(2), Math.cos(biggerBorder) * r + cx, Math.sin(biggerBorder) * r + cy);
context.fillText((mouseAngle * 180 / Math.PI).toFixed(2), Math.cos(mouseAngle) * r + cx, Math.sin(mouseAngle) * r + cy);
//update
setTimeout(function() { draw(); }, 10);
}
//getting mouse coordinates
function updateMousePos(evt)
{
var rect = document.getElementById("c").getBoundingClientRect();
mx = evt.clientX - rect.left;
my = evt.clientY - rect.top;
}

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<style>
body {
background-color: black;
}
canvas {
position: absolute;
margin: auto;
left: 0;
right: 0;
border: solid 1px white;
border-radius: 10px;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
<script type="application/javascript">
// Rotation here is being measured in Radians
// Given two 2D vectors A & B, the angle between them can be drawn from this formula
// A dot B = length(a) * length(b) * cos(angle)
// if the vectors are normalized (the length is 1) the formula becomes
// A dot B = cos(angle)
// angle = acos(a.x * b.x + a.y * b.y)
// So here you are concerned with the direction of the two vectors
// One will be the vector facing outward from the middle of your arc segment
// The other will be a directional vector from the point you want to do collision with to the center
// of the circle
var canvasWidth = 180;
var canvasHeight = 160;
var canvas = null;
var ctx = null;
var bounds = {top: 0.0, left: 0.0};
var circle = {
x: (canvasWidth * 0.5)|0,
y: (canvasHeight * 0.5)|0,
radius: 50.0,
rotation: 0.0, // In Radians
arcSize: 1.0
};
var point = {
x: 0.0,
y: 0.0
};
window.onmousemove = function(e) {
point.x = e.clientX - bounds.left;
point.y = e.clientY - bounds.top;
}
// runs after the page has loaded
window.onload = function() {
canvas = document.getElementById("canvas");
canvas.width = canvasWidth;
canvas.height = canvasHeight;
bounds = canvas.getBoundingClientRect();
ctx = canvas.getContext("2d");
loop();
}
function loop() {
// Update Circle Rotation
circle.rotation = circle.rotation + 0.025;
if (circle.rotation > 2*Math.PI) {
circle.rotation = 0.0;
}
// Vector A (Point Pos -> Circle Pos)
var aX = circle.x - point.x;
var aY = circle.y - point.y;
var aLength = Math.sqrt(aX * aX + aY * aY);
// Vector B (The direction the middle of the arc is facing away from the circle)
var bX = Math.sin(circle.rotation);
var bY =-Math.cos(circle.rotation); // -1 is facing upward, not +1
var bLength = 1.0;
// Normalize vector A
aX = aX / aLength;
aY = aY / aLength;
// Are we inside the arc segment?
var isInsideRadius = aLength < circle.radius;
var isInsideAngle = Math.abs(Math.acos(aX * bX + aY * bY)) < circle.arcSize * 0.5;
var isInsideArc = isInsideRadius && isInsideAngle;
// Clear the screen
ctx.fillStyle = "gray";
ctx.fillRect(0,0,canvasWidth,canvasHeight);
// Draw the arc
ctx.strokeStyle = isInsideArc ? "green" : "black";
ctx.beginPath();
ctx.moveTo(circle.x,circle.y);
ctx.arc(
circle.x,
circle.y,
circle.radius,
circle.rotation - circle.arcSize * 0.5 + Math.PI * 0.5,
circle.rotation + circle.arcSize * 0.5 + Math.PI * 0.5,
false
);
ctx.lineTo(circle.x,circle.y);
ctx.stroke();
// Draw the point
ctx.strokeStyle = "black";
ctx.fillStyle = "darkred";
ctx.beginPath();
ctx.arc(
point.x,
point.y,
5.0,
0.0,
2*Math.PI,
false
);
ctx.fill();
ctx.stroke();
// This is better to use then setTimeout()
// It automatically syncs the loop to 60 fps for you
requestAnimationFrame(loop);
}
</script>
</body>
</html>

Javascript Canvas apply Radial Gradient to Segment?

I am trying to create a shadow system for my 2D Game in a HTML5 Canvas. Right now, I am rendering my shadows like so:
function drawShadows(x, y, width) {
if (shadowSprite == null) {
shadowSprite = document.createElement('canvas');
var tmpCtx = shadowSprite.getContext('2d');
var shadowBlur = 20;
shadowSprite.width = shadowResolution;
shadowSprite.height = shadowResolution;
var grd = tmpCtx.createLinearGradient(-(shadowResolution / 4), 0,
shadowResolution, 0);
grd.addColorStop(0, "rgba(0, 0, 0, 0.1)");
grd.addColorStop(1, "rgba(0, 0, 0, 0)");
tmpCtx.fillStyle = grd;
tmpCtx.shadowBlur = shadowBlur;
tmpCtx.shadowColor = "#000";
tmpCtx.fillRect(0, 0, shadowResolution, shadowResolution);
}
graph.save();
graph.rotate(sun.getDir(x, y));
graph.drawImage(shadowSprite, 0, -(width / 2), sun.getDist(x, y), width);
graph.restore();
}
This renders a cube with a linear gradient that fades from black to alpha 0.
This however does not produce a realistic result, since it will always be a rectangle. Here is an illustration to describe the problem:
Sorry i'm not very artistic. It would not be an issue to draw the trapezoid shape. (Seen in blue). The issue is that I still there to be a gradient. Is it possible to draw a shape like that with a gradient?

The canvas is very flexible. Almost anything is possible. This example draws the light being cast. But it can just as easily be the reverse. Draw the shadows as a gradient.
If you are after realism then instead of rendering a gradient for the lighting (or shadows) use the shape created to set a clipping area and then render a accurate lighting and shadow solution.
With lineTo and gradients you can create any shape and gradient you my wish. Also to get the best results use globalCompositeOperation as they have a large variety of filters.
The demo just shows how to mix a gradient and a shadow map. (Very basic no recursion implemented, and shadows are just approximations.)
var canvas = document.getElementById("canV");
var ctx = canvas.getContext("2d");
var mouse = {
x:0,
y:0,
};
function mouseMove(event){
mouse.x = event.offsetX; mouse.y = event.offsetY;
if(mouse.x === undefined){ mouse.x = event.clientX; mouse.y = event.clientY;}
}
// add mouse controls
canvas.addEventListener('mousemove',mouseMove);
var boundSize = 10000; // a number....
var createImage = function(w,h){ // create an image
var image;
image = document.createElement("canvas");
image.width = w;
image.height = h;
image.ctx = image.getContext("2d");
return image;
}
var directionC = function(x,y,xx,yy){ // this should be inLine but the angles were messing with my head
var a; // so moved it out here
a = Math.atan2(yy - y, xx - x); // for clarity and the health of my sanity
return (a + Math.PI * 2) % (Math.PI * 2); // Dont like negative angles.
}
// Create background image
var back = createImage(20, 20);
back.ctx.fillStyle = "#333";
back.ctx.fillRect(0, 0, 20, 20);
// Create background image
var backLight = createImage(20, 20);
backLight .ctx.fillStyle = "#ACD";
backLight .ctx.fillRect(0, 0, 20, 20);
// create circle image
var circle = createImage(64, 64);
circle.ctx.fillStyle = "red";
circle.ctx.beginPath();
circle.ctx.arc(32, 32, 30, 0, Math.PI * 2);
circle.ctx.fill();
// create some circles semi random
var circles = [];
circles.push({
x : 200 * Math.random(),
y : 200 * Math.random(),
scale : Math.random() * 0.8 + 0.3,
});
circles.push({
x : 200 * Math.random() + 200,
y : 200 * Math.random(),
scale : Math.random() * 0.8 + 0.3,
});
circles.push({
x : 200 * Math.random() + 200,
y : 200 * Math.random() + 200,
scale : Math.random() * 0.8 + 0.3,
});
circles.push({
x : 200 * Math.random(),
y : 200 * Math.random() + 200,
scale : Math.random() * 0.8 + 0.3,
});
// shadows on for each circle;
var shadows = [{},{},{},{}];
var update = function(){
var c, dir, dist, x, y, x1, y1, x2, y2, dir1, dir2, aAdd, i, j, s, s1 ,nextDir, rev, revId;
rev = false; // if inside a circle reverse the rendering.
// set up the gradient at the mouse pos
var g = ctx.createRadialGradient(mouse.x, mouse.y, canvas.width * 1.6, mouse.x, mouse.y, 2);
// do each circle and work out the two shadow lines coming from it.
for(var i = 0; i < circles.length; i++){
c = circles[i];
dir = directionC(mouse.x, mouse.y, c.x, c.y);
dist = Math.hypot(mouse.x - c.x, mouse.y - c.y);
// cludge factor. Could not be bother with the math as the light sourse nears an object
if(dist < 30* c.scale){
rev = true;
revId = i;
}
aAdd = (Math.PI / 2) * (0.5 / (dist - 30 * c.scale));
x1 = Math.cos(dir - (Math.PI / 2 + aAdd)) * 30 * c.scale;
y1 = Math.sin(dir - (Math.PI / 2 + aAdd)) * 30 * c.scale;
x2 = Math.cos(dir + (Math.PI / 2 + aAdd)) * 30 * c.scale;
y2 = Math.sin(dir + (Math.PI / 2 + aAdd)) * 30 * c.scale;
// direction of both shadow lines
dir1 = directionC(mouse.x, mouse.y, c.x + x1, c.y + y1);
dir2 = directionC(mouse.x, mouse.y, c.x + x2, c.y + y2);
// create the shadow object to hold details
shadows[i].dir = dir;
shadows[i].d1 = dir1;
if (dir2 < dir1) { // make sure second line is always greater
dir2 += Math.PI * 2;
}
shadows[i].d2 = dir2;
shadows[i].x1 = (c.x + x1); // set the shadow start pos
shadows[i].y1 = (c.y + y1);
shadows[i].x2 = (c.x + x2); // for both lines
shadows[i].y2 = (c.y + y2);
shadows[i].circle = c; // ref the circle
shadows[i].dist = dist; // set dist from light
shadows[i].branch1 = undefined; //.A very basic tree for shadows that interspet other object
shadows[i].branch2 = undefined; //
shadows[i].branch1Dist = undefined;
shadows[i].branch2Dist = undefined;
shadows[i].active = true; // false if the shadow is in a shadow
shadows[i].id = i;
}
shadows.sort(function(a,b){ // sort by distance from light
return a.dist - b.dist;
});
// cull shdows with in shadows and connect circles with joined shadows
for(i = 0; i < shadows.length; i++){
s = shadows[i];
for(j = i + 1; j < shadows.length; j++){
s1 = shadows[j];
if(s1.d1 > s.d1 && s1.d2 < s.d2){ // if shadow in side another
s1.active = false; // cull it
}else
if(s.d1 > s1.d1 && s.d1 < s1.d2){ // if shodow intercepts going twards light
s1.branch1 = s;
s.branch1Dist = s1.dist - s.dist;
s.active = false;
}else
if(s.d2 > s1.d1 && s.d2 < s1.d2){ // away from light
s.branch2 = s1;
s.branch2Dist = s1.dist - s.dist;
s1.active = false;
}
}
}
// keep it quick so not using filter
// filter culled shadows
var shadowsShort = [];
for (i = 0; i < shadows.length; i++) {
if ((shadows[i].active && !rev) || (rev && shadows[i].id === revId)) { // to much hard work makeng shadow from inside the circles. Was a good idea at the time. But this i just an example after all;
shadowsShort.push(shadows[i])
}
}
// sort shadows in clock wise render order
if(rev){
g.addColorStop(0.3, "rgba(210,210,210,0)");
g.addColorStop(0.6, "rgba(128,128,128,0.5)");
g.addColorStop(1, "rgba(0,0,0,0.9)");
shadowsShort.sort(function(a,b){
return b.dir - a.dir;
});
// clear by drawing background image.
ctx.drawImage(backLight, 0, 0, canvas.width, canvas.height);
}else{
g.addColorStop(0.3, "rgba(0,0,0,0)");
g.addColorStop(0.6, "rgba(128,128,128,0.5)");
g.addColorStop(1, "rgba(215,215,215,0.9)");
shadowsShort.sort(function(a,b){
return a.dir - b.dir;
});
// clear by drawing background image.
ctx.drawImage(back, 0, 0, canvas.width, canvas.height);
}
// begin drawin the light area
ctx.fillStyle = g; // set the gradient as the light
ctx.beginPath();
for(i = 0; i < shadowsShort.length; i++){ // for each shadow move in to the light across the circle and then back out away from the light
s = shadowsShort[i];
x = s.x1 + Math.cos(s.d1) * boundSize;
y = s.y1 + Math.sin(s.d1) * boundSize;
if (i === 0) { // if the start move to..
ctx.moveTo(x, y);
} else {
ctx.lineTo(x, y);
}
ctx.lineTo(s.x1, s.y1);
if (s.branch1 !== undefined) { // if braching. (NOTE this is not recursive. the correct solution would to math this a function and use recursion to climb in an out)
s = s.branch1;
x = s.x1 + Math.cos(s.d1) * s.branch1Dist;
y = s.y1 + Math.sin(s.d1) * s.branch1Dist;
ctx.lineTo(x, y);
ctx.lineTo(s.x1, s.y1);
}
ctx.lineTo(s.x2, s.y2);
if (s.branch2 !== undefined) {
x = s.x2 + Math.cos(s.d2) * s.branch2Dist;
y = s.y2 + Math.sin(s.d2) * s.branch2Dist;
ctx.lineTo(x, y);
s = s.branch2;
ctx.lineTo(s.x2, s.y2);
}
x = s.x2 + Math.cos(s.d2) * boundSize;
y = s.y2 + Math.sin(s.d2) * boundSize;
ctx.lineTo(x, y);
// now fill in the light between shadows
s1 = shadowsShort[(i + 1) % shadowsShort.length];
nextDir = s1.d1;
if(rev){
if (nextDir > s.d2) {
nextDir -= Math.PI * 2
}
}else{
if (nextDir < s.d2) {
nextDir += Math.PI * 2
}
}
x = Math.cos((nextDir+s.d2)/2) * boundSize + canvas.width / 2;
y = Math.sin((nextDir+s.d2)/2) * boundSize + canvas.height / 2;
ctx.lineTo(x, y);
}
// close the path.
ctx.closePath();
// set the comp to lighten or multiply
if(rev){
ctx.globalCompositeOperation ="multiply";
}else{
ctx.globalCompositeOperation ="lighter";
}
// draw the gradient
ctx.fill()
ctx.globalCompositeOperation ="source-over";
// draw the circles
for (i = 0; i < circles.length; i++) {
c = circles[i];
ctx.drawImage(circle, c.x - 32 * c.scale, c.y - 32 * c.scale, 64 * c.scale, 64 * c.scale);
}
// feed the herbervors.
window.requestAnimationFrame(update);
}
update();
.canC { width:400px; height:400px;}
<canvas class="canC" id="canV" width=400 height=400></canvas>