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canvasRenderer.js
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canvasRenderer.js
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class ViewPort {
constructor(width, height) {
this.width = width;
this.height = height;
this.position = new Vector2(),
this.previousRenderedPosition = new Vector2();
this._position = new Vector2();
}
getAssetScreenPosition(asset) {
this._position.set(
asset.position.x - this.position.x,
asset.position.y - this.position.y
);
// convert cartesian to isometric
this._position.set(
this._position.x - this._position.y,
(this._position.x + this._position.y) / 2
);
return this._position.set(
this._position.x - asset.height / 2 + this.height / 2,
this._position.y - asset.width / 2 + this.width / 2
);
}
resolveScreenPosition(x, y) {
x = x - this.width / 2;
y = y - this.height / 2;
// convert isometric to cartesian
x = (2 * y + x) / 2;
y = 2 * y - x;
x = x + this.position.x;
y = y + this.position.y;
return this._position.set(x, y);
}
}
class CollisionHelper {
constructor() {
this.assets = [];
}
addAsset(...assets) {
this.assets.push(...assets);
}
getNearestBlockingAssets(asset) {
// ToDo
return this.assets;
}
}
export function createCanvasRenderer() {
const simulationStep = 1/120; // resolution of simulations (ms)
const simulationLimit = 120; // max allowed simulations before next render
let simulationCount = 0;
let simulationLag = 0;
let elapsedTime = 0;
let prevTimeStamp = 0;
let gScene;
function updateLayer(layer) {
layer.updatePhysics(simulationStep, gScene.collisionHelper);
}
function updateScene() {
gScene.layers.forEach(updateLayer);
}
function drawLayer(layer) {
layer.render(gScene.viewPort);
}
function drawScene() {
gScene.layers.forEach(drawLayer);
}
function simulate(elapsedTime) {
simulationCount = 0;
simulationLag += elapsedTime;
while (simulationLag > simulationStep) {
simulationLag -= simulationStep;
updateScene();
if (++simulationCount >= simulationLimit) {
simulationLag = 0;
break;
}
}
}
function render(timeStamp = performance.now()) {
elapsedTime = (timeStamp - (prevTimeStamp || performance.now())) * 0.001;
simulate(elapsedTime);
drawScene();
prevTimeStamp = timeStamp;
requestAnimationFrame(render);
}
return {
render: (scene) => {
gScene = scene;
render();
},
pause: () => {},
};
};
export function createScene(width = window.innerWidth, height = window.innerHeight) {
const collisionHelper = new CollisionHelper();
const layers = [];
const viewPort = new ViewPort(width, height);
createNewLayer();
return {
collisionHelper,
layers,
viewPort,
createNewLayer,
};
function createNewLayer(zIndex = 0, containerElement) {
const layer = createLayer(containerElement);
layer.setSize(width, height);
layer.setZIndex(zIndex);
return layers.push(layer) - 1;
};
}
function createLayer(containerElement = getBodyElement()) {
const canvas = document.createElement('canvas');
const drawContext = canvas.getContext('2d');
const assets = [];
const clearCanvas = () => drawContext.clearRect(0, 0, canvas.width, canvas.height);
containerElement.appendChild(canvas);
centerCanvas(canvas);
return {
assets,
addAsset: (...asset) => {
return assets.push(...asset) - 1;
},
hideAsset: (index) => {
},
updatePhysics: (dt, collisionHelper) => {
assets.forEach((asset) => asset.updatePosition && asset.updatePosition(dt, collisionHelper));
},
render: (viewPort) => {
if (assets.some((asset) => asset.shouldReRender(viewPort))) {
clearCanvas();
assets.sort(depthSortAssets);
assets.forEach((asset) => asset.render(drawContext, viewPort));
viewPort.previousRenderedPosition.copy(viewPort.position);
}
},
clear: clearCanvas,
setSize: (width = window.innerWidth, height = window.innerHeight) => {
canvas.width = width;
canvas.height = height;
},
setZIndex: (i = 0) => {
canvas.style['z-index'] = i;
},
};
}
function depthSortAssets(assetA, assetB) {
return Number(assetA.depth > assetB.depth);
}
function centerCanvas(canvas) {
canvas.style.position = 'absolute';
canvas.style.left = '50%';
canvas.style.top = '50%';
canvas.style.transform = 'translate(-50%, -50%)';
}
function getBodyElement() {
return document.querySelector('body');
}