(() => {
const m = new Float32Array([
0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0,
0, 0, 0, 0
])
const pointSize = Math.max(Math.min(10, ~~(innerWidth / 70)), 3);
const vert = `
attribute vec3 vec;
uniform mat4 mat;
void main(void) {
gl_Position = mat * vec4(vec, 1.);
gl_PointSize = ${pointSize}.;
}
`
const frag = `
#ifdef GL_ES
precision highp float;
#endif
void main(void) {
vec2 uv = gl_FragCoord.xy / vec2(500., 500.);
gl_FragColor = vec4(uv.x, 0., cos(uv.y * 60.), .4);
}
`
document.body.style.background = '#333'
const gl = document.body
.appendChild(document.createElement('canvas'))
.getContext('webgl')
Object.assign(gl.canvas.style, {
position: 'absolute',
left: '50%',
top: '50%',
transform: 'translate(-50%, -50%)',
outline: '1px solid gray'
})
with (gl) {
const NUM = 3
const s = .5;
const verts = [
-s, -s, 0,
s, -s, 0,
-s, s, 0,
s, s, 0,
]
// 1.0, 1.0,
// -1.0, 1.0,
// 1.0, -1.0,
// -1.0, -1.0,
// for (let i = 0; i < NUM; i++) {
// verts.push(
// Math.random() * 1 - 0.5,
// Math.random() * 1 - 0.5,
// Math.random() * 1 - 0.5
// )
// }
const leng = verts.length / 3
bindBuffer(ARRAY_BUFFER, createBuffer())
bufferData(ARRAY_BUFFER, new Float32Array(verts), STATIC_DRAW)
const vs = createShader(VERTEX_SHADER)
shaderSource(vs, vert)
compileShader(vs)
const fs = createShader(FRAGMENT_SHADER)
const sp = createProgram()
shaderSource(fs, frag)
compileShader(fs)
attachShader(sp, vs)
attachShader(sp, fs)
linkProgram(sp)
useProgram(sp)
const vec = getAttribLocation(sp, 'vec')
vertexAttribPointer(vec, 3, FLOAT, false, 0, 0)
enableVertexAttribArray(vec)
const matLoc = getUniformLocation(sp, 'mat')
function rot(x, y, z) {
// https://wikimedia.org/api/rest_v1/media/math/render/svg/a8e16f4967571b7a572d1a19f3f6468512f9843e
const sinA = Math.sin(x)
const cosA = Math.cos(x)
const sinB = Math.sin(y)
const cosB = Math.cos(y)
const sinY = Math.sin(z)
const cosY = Math.cos(z)
m[0] = cosA * cosB
m[1] = cosA * sinB * sinY - sinA * cosY
m[2] = cosA * sinB * cosY + sinA * sinY
m[3] = 0
m[4] = sinA * cosB
m[5] = sinA * sinB * sinY + cosA * cosY
m[6] = sinA * sinB * cosY - cosA * sinY
m[7] = 0
m[8] = -sinB
m[9] = cosB * sinY
m[10] = cosB * cosY
m[11] = m[12] = m[13] = 0
m[15] = 1
uniformMatrix4fv(matLoc, false, m)
}
onresize = () => {
const { canvas } = gl
const size = Math.min(innerWidth, innerHeight) - 20
canvas.width = canvas.height = size
viewport(0, 0, size, size)
}
onresize()
let rx = 0, ry = 0
disable(DEPTH_TEST)
enable(BLEND)
blendFunc(SRC_ALPHA, ONE_MINUS_SRC_ALPHA)
function loop() {
rot(rx += .01, ry += .01, 0)
clearColor(0, 0, 0, 1)
clear(COLOR_BUFFER_BIT)
drawArrays(TRIANGLE_STRIP, 0, leng)
window.requestAnimationFrame(loop)
}
loop()
}
})()