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webgl-multiple-views-items.html
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<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
<title>WebGL - Multiple Views Items</title>
<style>
html, body {
margin: 0;
height: 100%;
}
#content {
margin: 10px;
}
#canvas {
position: absolute;
top: 0;
width: 100%;
height: 100%;
z-index: -1;
display: block;
}
.item {
display: inline-block;
margin: 1em;
padding: 1em;
}
.label {
margin-top: 0.5em;
}
.view {
width: 250px;
height: 250px;
border: 1px solid black;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
<div id="content"></div>
</body>
<!--
for most samples webgl-utils only provides shader compiling/linking and
canvas resizing because why clutter the examples with code that's the same in every sample.
See https://webglfundamentals.org/webgl/lessons/webgl-boilerplate.html
and https://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
for webgl-utils, m3, m4, and webgl-lessons-ui.
-->
<script src="resources/webgl-utils.js"></script>
<script src="resources/m4.js"></script>
<script src="resources/primitives.js"></script>
<!-- vertex shader -->
<script id="vertex-shader-3d" type="x-shader/x-vertex">
attribute vec4 a_position;
attribute vec3 a_normal;
uniform mat4 u_matrix;
varying vec3 v_color;
void main() {
// Multiply the position by the matrix.
gl_Position = u_matrix * a_position;
// Pass the normal as the color to the fragment shader.
v_color = a_normal * .5 + .5;
}
</script>
<!-- fragment shader -->
<script id="fragment-shader-3d" type="x-shader/x-fragment">
precision mediump float;
// Passed in from the vertex shader.
varying vec3 v_color;
void main() {
gl_FragColor = vec4(v_color, 1);
}
</script>
<script>
'use strict';
function main() {
// Get A WebGL context
/** @type {HTMLCanvasElement} */
const canvas = document.querySelector('#canvas');
const gl = canvas.getContext('webgl');
if (!gl) {
return;
}
// setup GLSL programs
// compiles shaders, links program, looks up locations
const programInfo = webglUtils.createProgramInfo(gl, ['vertex-shader-3d', 'fragment-shader-3d']);
// create buffers and fill with data for various things.
const bufferInfos = [
primitives.createCubeBufferInfo(
gl,
1, // width
1, // height
1, // depth
),
primitives.createSphereBufferInfo(
gl,
0.5, // radius
8, // subdivisions around
6, // subdivisions down
),
primitives.createTruncatedConeBufferInfo(
gl,
0.5, // bottom radius
0, // top radius
1, // height
6, // subdivisions around
1, // subdivisions down
),
];
function createElem(type, parent, className) {
const elem = document.createElement(type);
parent.appendChild(elem);
if (className) {
elem.className = className;
}
return elem;
}
function randArrayElement(array) {
return array[Math.random() * array.length | 0];
}
function rand(min, max) {
if (max === undefined) {
max = min;
min = 0;
}
return Math.random() * (max - min) + min;
}
const contentElem = document.querySelector('#content');
const items = [];
const numItems = 100;
for (let i = 0; i < numItems; ++i) {
const outerElem = createElem('div', contentElem, 'item');
const viewElem = createElem('div', outerElem, 'view');
const labelElem = createElem('div', outerElem, 'label');
labelElem.textContent = `Item ${i + 1}`;
const bufferInfo = randArrayElement(bufferInfos);
const color = [rand(1), rand(1), rand(1), 1];
items.push({
bufferInfo,
color,
element: viewElem,
});
}
function degToRad(d) {
return d * Math.PI / 180;
}
const fieldOfViewRadians = degToRad(60);
function drawScene(projectionMatrix, cameraMatrix, worldMatrix, bufferInfo) {
// Clear the canvas AND the depth buffer.
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
// Make a view matrix from the camera matrix.
const viewMatrix = m4.inverse(cameraMatrix);
let mat = m4.multiply(projectionMatrix, viewMatrix);
mat = m4.multiply(mat, worldMatrix);
gl.useProgram(programInfo.program);
// ------ Draw the bufferInfo --------
// Setup all the needed attributes.
webglUtils.setBuffersAndAttributes(gl, programInfo, bufferInfo);
// Set the uniform
webglUtils.setUniforms(programInfo, {
u_matrix: mat,
});
webglUtils.drawBufferInfo(gl, bufferInfo);
}
function render(time) {
time *= 0.001; // convert to seconds
webglUtils.resizeCanvasToDisplaySize(gl.canvas);
gl.enable(gl.CULL_FACE);
gl.enable(gl.DEPTH_TEST);
gl.enable(gl.SCISSOR_TEST);
// move the canvas to top of the current scroll position
gl.canvas.style.transform = `translateY(${window.scrollY}px)`;
for (const {bufferInfo, element, color} of items) {
const rect = element.getBoundingClientRect();
if (rect.bottom < 0 || rect.top > gl.canvas.clientHeight ||
rect.right < 0 || rect.left > gl.canvas.clientWidth) {
continue; // it's off screen
}
const width = rect.right - rect.left;
const height = rect.bottom - rect.top;
const left = rect.left;
const bottom = gl.canvas.clientHeight - rect.bottom;
gl.viewport(left, bottom, width, height);
gl.scissor(left, bottom, width, height);
gl.clearColor(...color);
const aspect = width / height;
const near = 1;
const far = 2000;
// Compute a perspective projection matrix
const perspectiveProjectionMatrix =
m4.perspective(fieldOfViewRadians, aspect, near, far);
// Compute the camera's matrix using look at.
const cameraPosition = [0, 0, -2];
const target = [0, 0, 0];
const up = [0, 1, 0];
const cameraMatrix = m4.lookAt(cameraPosition, target, up);
// rotate the item
const rTime = time * 0.2;
const worldMatrix = m4.xRotate(m4.yRotation(rTime), rTime);
drawScene(perspectiveProjectionMatrix, cameraMatrix, worldMatrix, bufferInfo);
}
requestAnimationFrame(render);
}
requestAnimationFrame(render);
}
main();
</script>
</html>