Tinkering with code and algorithms for fun
Published
Edited
Jan 17, 2020
25 stars
compiledWaltBuffer = walt.compile(waltSource).buffer()
function instantiate(compiledBuffer) {
const ctx = waltCanvas.getContext("2d");
const canvas = waltCanvas;
const imgData = ctx.createImageData(canvas.width, canvas.height);
const canvasWidth = canvas.width;
const canvasHeight = canvas.height;
const getCanvasWidth = () => canvasWidth;
const getCanvasHeight = () => canvasHeight;
const env = {
getCanvasWidth,
getCanvasHeight,
log: (val) => {
console.log(val);
}
};
// Arrange for resize
window.addEventListener('resize', onresize, false);
return WebAssembly.instantiate(compiledBuffer, { env }).then(result => {
const exports = result.instance.exports;
const memory = exports.memory;
const { width, height } = canvas;
const wh = width * height;
// Grow memory to required size
const pages = 1 + ((20 * wh + 256) >> 16);
memory.grow(pages);
const heap = memory.buffer;
const HEAP_START = 65536;
const imageArray = new Uint8ClampedArray(heap, HEAP_START, 4 * wh);
const image32Array = new Uint32Array(heap, HEAP_START, wh);
const forceArray = new Int32Array(heap, HEAP_START + 4 * wh, wh);
const statusArray = new Int32Array(heap, HEAP_START + 8 * wh, wh);
const uArray = new Int32Array(heap, HEAP_START + 12 * wh, wh);
const velArray = new Int32Array(heap, HEAP_START + 16 * wh, wh);
const colorRampArray = new Uint32Array(heap, HEAP_START + 20 * wh, 256);
colorRampArray.set(colorRamp.RGBA32);
// we clamp to the range [0, width-1], so -1 is a
// way to indicate there was no previous mouse value
let lastMouseX = -1;
let lastMouseY = -1;
const applyBrush = exports.applyBrush;
canvas.onmousedown = (e) => {
e.preventDefault();
let bbox = canvas.getBoundingClientRect();
let mouseX = Math.round(e.clientX - bbox.left * (width / bbox.width));
let mouseY = Math.round(e.clientY - bbox.top * (height / bbox.height));
mouseX = Math.max(1, Math.min(canvasWidth-1, mouseX));
mouseY = Math.max(1, Math.min(canvasHeight-1, mouseY));
lastMouseX = mouseX;
lastMouseY = mouseY;
applyBrush(mouseX, mouseY, brushRadius);
};
canvas.onmousemove = (e) => {
e.preventDefault();
let bbox = canvas.getBoundingClientRect();
let mouseX = Math.round(e.clientX - bbox.left * (width / bbox.width));
let mouseY = Math.round(e.clientY - bbox.top * (height / bbox.height));
mouseX = Math.max(1, Math.min(canvasWidth-1, mouseX));
mouseY = Math.max(1, Math.min(canvasHeight-1, mouseY));
if (lastMouseX !== -1 && lastMouseY !== -1) {
const dx = mouseX - lastMouseX;
const dy = mouseY - lastMouseY;
const r = Math.sqrt(dx*dx + dy*dy);
for (let t = 0; t <= r; t += brushRadius+1 >> 1) {
const currX = lastMouseX + ((mouseX - lastMouseX) * (t / r)) | 0;
const currY = lastMouseY + ((mouseY - lastMouseY) * (t / r)) | 0;
applyBrush(currX, currY, brushRadius);
forceArray[currY * width + currX] = 0x3FFFFFFF;
}
applyBrush(mouseX, mouseY, brushRadius);
lastMouseX = mouseX;
lastMouseY = mouseY;
}
};
canvas.onmouseout = canvas.onmouseup = (e) => {
e.preventDefault();
lastMouseX = -1;
lastMouseY = -1;
};
// fake mouse events when triggering touch events
canvas.addEventListener("touchstart", function (e) {
e.preventDefault();
var touch = e.touches[0];
var mouseEvent = new MouseEvent("mousedown", {
clientX: touch.clientX,
clientY: touch.clientY
});
canvas.dispatchEvent(mouseEvent);
}, false);
canvas.addEventListener("touchend", function (e) {
e.preventDefault();
var touch = e.touches[0];
var mouseEvent = new MouseEvent("mouseup", {
clientX: touch.clientX,
clientY: touch.clientY
});
canvas.dispatchEvent(mouseEvent);
}, false);
canvas.addEventListener("touchmove", function (e) {
e.preventDefault();
var touch = e.touches[0];
var mouseEvent = new MouseEvent("mousemove", {
clientX: touch.clientX,
clientY: touch.clientY
});
canvas.dispatchEvent(mouseEvent);
}, false);
let raf;
let raindrop = 0x3FFFFFFF;
function run() {
if (rainNoise) {
const raindrop2 = raindrop^0xFFFFFFFF;
const j = width + (wh-(width*2)) * Math.random() | 0;
forceArray[j-width-1] = raindrop2;
forceArray[j-width] = raindrop2;
forceArray[j-width+1] = raindrop2;
forceArray[j-1] = raindrop2;
forceArray[j] = raindrop2;
forceArray[j+1] = raindrop;
forceArray[j+width-1] = raindrop2;
forceArray[j+width] = raindrop2;
forceArray[j+width+1] = raindrop2;
raindrop = raindrop2;
}
exports.step();
imgData.data.set(imageArray);
ctx.putImageData(imgData, 0, 0);
raf = requestAnimationFrame(run, 0);
}
function cancel() {
cancelAnimationFrame(raf);
}
exports.init(useColormap ? 1 : 0);
return { run, cancel, canvas };
});
}
One platform to build and deploy the best data apps
Experiment and prototype by building visualizations in live JavaScript notebooks. Collaborate with your team and decide which concepts to build out.
Use Observable Framework to build data apps locally. Use data loaders to build in any language or library, including Python, SQL, and R.
Seamlessly deploy to Observable. Test before you ship, use automatic deploy-on-commit, and ensure your projects are always up-to-date.