From 4be773679a5e0bf4b3fb53c4b559dd83d690a310 Mon Sep 17 00:00:00 2001
From: akira-cn <akira.cn@gmail.com>
Date: Wed, 15 Apr 2020 16:59:53 +0800
Subject: [PATCH] update

---
 webgl_particles/app.js     | 135 +++++++++++++++++++++++++++++++++++++
 webgl_particles/index.html |  12 ++++
 2 files changed, 147 insertions(+)
 create mode 100644 webgl_particles/app.js
 create mode 100644 webgl_particles/index.html

diff --git a/webgl_particles/app.js b/webgl_particles/app.js
new file mode 100644
index 0000000..54b839e
--- /dev/null
+++ b/webgl_particles/app.js
@@ -0,0 +1,135 @@
+const canvas = document.querySelector('canvas');
+const gl = canvas.getContext('webgl');
+
+const vertex = `
+  attribute vec2 position;
+
+  uniform float u_rotation;
+  uniform float u_time;
+  uniform float u_duration;
+  uniform float u_scale;
+  uniform vec2 u_dir;
+
+  varying float vP;
+
+  void main() {
+    float p = min(1.0, u_time / u_duration);
+    float rad = u_rotation + 3.14 * 10.0 * p;
+    float scale = u_scale * p * (2.0 - p);
+    vec2 offset = 2.0 * u_dir * p * p;
+    mat3 translateMatrix = mat3(
+      1.0, 0.0, 0.0,
+      0.0, 1.0, 0.0,
+      offset.x, offset.y, 1.0
+    );
+    mat3 rotateMatrix = mat3(
+      cos(rad), sin(rad), 0.0,
+      -sin(rad), cos(rad), 0.0,
+      0.0, 0.0, 1.0
+    );
+    mat3 scaleMatrix = mat3(
+      scale, 0.0, 0.0,
+      0.0, scale, 0.0,
+      0.0, 0.0, 1.0
+    );
+    gl_PointSize = 1.0;
+    vec3 pos = translateMatrix * rotateMatrix * scaleMatrix * vec3(position, 1.0);
+    gl_Position = vec4(pos, 1.0);
+    vP = p;
+  }
+`;
+
+const fragment = `
+  precision mediump float;
+  
+  uniform vec4 u_color;
+
+  varying float vP;
+
+  void main()
+  {
+    gl_FragColor.xyz = u_color.xyz;
+    gl_FragColor.a = (1.0 - vP) * u_color.a;
+  }    
+`;
+
+const vertexShader = gl.createShader(gl.VERTEX_SHADER);
+gl.shaderSource(vertexShader, vertex);
+gl.compileShader(vertexShader);
+
+const fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);
+gl.shaderSource(fragmentShader, fragment);
+gl.compileShader(fragmentShader);
+
+const program = gl.createProgram();
+gl.attachShader(program, vertexShader);
+gl.attachShader(program, fragmentShader);
+gl.linkProgram(program);
+gl.useProgram(program);
+
+const position = new Float32Array([
+  -1, -1,
+  0, 1,
+  1, -1,
+]);
+const bufferId = gl.createBuffer();
+gl.bindBuffer(gl.ARRAY_BUFFER, bufferId);
+gl.bufferData(gl.ARRAY_BUFFER, position, gl.STATIC_DRAW);
+
+const vPosition = gl.getAttribLocation(program, 'position');
+gl.vertexAttribPointer(vPosition, 2, gl.FLOAT, false, 0, 0);
+gl.enableVertexAttribArray(vPosition);
+
+function randomTriangles() {
+  const u_color = [Math.random(), Math.random(), Math.random(), 1.0]; // 随机颜色
+  const u_rotation = Math.random() * Math.PI; // 初始旋转角度
+  const u_scale = Math.random() * 0.05 + 0.03; // 初始大小
+  const u_time = 0;
+  const u_duration = 3.0; // 持续3秒钟
+
+  const rad = Math.random() * Math.PI * 2;
+  const u_dir = [Math.cos(rad), Math.sin(rad)]; // 运动方向
+  const startTime = performance.now();
+
+  return {u_color, u_rotation, u_scale, u_time, u_duration, u_dir, startTime};
+}
+
+function setUniforms(gl, {u_color, u_rotation, u_scale, u_time, u_duration, u_dir}) {
+  let loc = gl.getUniformLocation(program, 'u_color');
+  gl.uniform4fv(loc, u_color);
+
+  loc = gl.getUniformLocation(program, 'u_rotation');
+  gl.uniform1f(loc, u_rotation);
+
+  loc = gl.getUniformLocation(program, 'u_scale');
+  gl.uniform1f(loc, u_scale);
+
+  loc = gl.getUniformLocation(program, 'u_time');
+  gl.uniform1f(loc, u_time);
+
+  loc = gl.getUniformLocation(program, 'u_duration');
+  gl.uniform1f(loc, u_duration);
+
+  loc = gl.getUniformLocation(program, 'u_dir');
+  gl.uniform2fv(loc, u_dir);
+}
+
+let triangles = [];
+function update(t) {
+  for(let i = 0; i < 5 * Math.random(); i++) {
+    triangles.push(randomTriangles());
+  }
+  gl.clear(gl.COLOR_BUFFER_BIT);
+  triangles.forEach((triangle) => {
+    triangle.u_time = (performance.now() - triangle.startTime) / 1000;
+    setUniforms(gl, triangle);
+    gl.drawArrays(gl.TRIANGLES, 0, position.length / 2);
+  });
+
+  triangles = triangles.filter((triangle) => {
+    return triangle.u_time <= triangle.u_duration;
+  });
+  requestAnimationFrame(update);
+}
+
+requestAnimationFrame(update);
diff --git a/webgl_particles/index.html b/webgl_particles/index.html
new file mode 100644
index 0000000..e3741a3
--- /dev/null
+++ b/webgl_particles/index.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <title>WebGL Hello world</title>
+</head>
+<body>
+  <canvas width="600" height="600"></canvas>
+  <script type="module" src="app.js"></script>
+</body>
+</html>
\ No newline at end of file