文章目录
写在前面
本期博主给大家推荐一个由HTML代码实现的、红蓝色线条组成的流光爱心，一起来看看吧。
完整代码
<!DOCTYPE html>
<!--<div class="menu__subheader"><br>微信公众号：雁卿雁卿呀-->
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>流光爱心</title>
<meta name="author" content="Logical Digit">
</head>
<!-- css部分 -->
<style>
body {
background-color: #000;
margin: 0;
overflow: hidden;
background-repeat: no-repeat;
}
</style>
<body>
<!-- 绘画爱心 -->
<canvas id="canvas" width="1400" height="600"></canvas>
<!-- js部分 -->
</body>
<script>
var canvas = document.getElementById("canvas");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
// Initialize the GL context
var gl = canvas.getContext('webgl');
if (!gl) {
console.error("Unable to initialize WebGL.");
}
//Time step
var dt = 0.015;
//Time
var time = 0.0;
//************** Shader sources **************
var vertexSource = `
attribute vec2 position;
void main() {
gl_Position = vec4(position, 0.0, 1.0);
}
`;
var fragmentSource = `
precision highp float;
uniform float width;
uniform float height;
vec2 resolution = vec2(width, height);
uniform float time;
#define POINT_COUNT 8
vec2 points[POINT_COUNT];
const float speed = -0.5;
const float len = 0.25;
float intensity = 0.9;
float radius = 0.015;
//https://www.shadertoy.com/view/MlKcDD
//Signed distance to a quadratic bezier
float sdBezier(vec2 pos, vec2 A, vec2 B, vec2 C){
vec2 a = B - A;
vec2 b = A - 2.0*B + C;
vec2 c = a * 2.0;
vec2 d = A - pos;
float kk = 1.0 / dot(b,b);
float kx = kk * dot(a,b);
float ky = kk * (2.0*dot(a,a)+dot(d,b)) / 3.0;
float kz = kk * dot(d,a);
float res = 0.0;
float p = ky - kx*kx;
float p3 = p*p*p;
float q = kx*(2.0*kx*kx - 3.0*ky) + kz;
float h = q*q + 4.0*p3;
if(h >= 0.0){
h = sqrt(h);
vec2 x = (vec2(h, -h) - q) / 2.0;
vec2 uv = sign(x)*pow(abs(x), vec2(1.0/3.0));
float t = uv.x + uv.y - kx;
t = clamp( t, 0.0, 1.0 );
// 1 root
vec2 qos = d + (c + b*t)*t;
res = length(qos);
}else{
float z = sqrt(-p);
float v = acos( q/(p*z*2.0) ) / 3.0;
float m = cos(v);
float n = sin(v)*1.732050808;
vec3 t = vec3(m + m, -n - m, n - m) * z - kx;
t = clamp( t, 0.0, 1.0 );
// 3 roots
vec2 qos = d + (c + b*t.x)*t.x;
float dis = dot(qos,qos);
res = dis;
qos = d + (c + b*t.y)*t.y;
dis = dot(qos,qos);
res = min(res,dis);
qos = d + (c + b*t.z)*t.z;
dis = dot(qos,qos);
res = min(res,dis);
res = sqrt( res );
}
return res;
}
//http://mathworld.wolfram.com/HeartCurve.html
vec2 getHeartPosition(float t){
return vec2(16.0 * sin(t) * sin(t) * sin(t),
-(13.0 * cos(t) - 5.0 * cos(2.0*t)
- 2.0 * cos(3.0*t) - cos(4.0*t)));
}
//https://www.shadertoy.com/view/3s3GDn
float getGlow(float dist, float radius, float intensity){
return pow(radius/dist, intensity);
}
float getSegment(float t, vec2 pos, float offset, float scale){
for(int i = 0; i < POINT_COUNT; i++){
points[i] = getHeartPosition(offset + float(i)*len + fract(speed * t) * 6.28);
}
vec2 c = (points[0] + points[1]) / 2.0;
vec2 c_prev;
float dist = 10000.0;
for(int i = 0; i < POINT_COUNT-1; i++){
//https://tinyurl.com/y2htbwkm
c_prev = c;
c = (points[i] + points[i+1]) / 2.0;
dist = min(dist, sdBezier(pos, scale * c_prev, scale * points[i], scale * c));
}
return max(0.0, dist);
}
void main(){
vec2 uv = gl_FragCoord.xy/resolution.xy;
float widthHeightRatio = resolution.x/resolution.y;
vec2 centre = vec2(0.5, 0.5);
vec2 pos = centre - uv;
pos.y /= widthHeightRatio;
//Shift upwards to centre heart
pos.y += 0.02;
float scale = 0.000015 * height;
float t = time;
//Get first segment
float dist = getSegment(t, pos, 0.0, scale);
float glow = getGlow(dist, radius, intensity);
vec3 col = vec3(0.0);
//White core
col += 10.0*vec3(smoothstep(0.003, 0.001, dist));
//Pink glow
col += glow * vec3(0.94,0.14,0.4);
//Get second segment
dist = getSegment(t, pos, 3.4, scale);
glow = getGlow(dist, radius, intensity);
//White core
col += 10.0*vec3(smoothstep(0.003, 0.001, dist));
//Blue glow
col += glow * vec3(0.2,0.6,1.0);
//Tone mapping
col = 1.0 - exp(-col);
//Output to screen
gl_FragColor = vec4(col,1.0);
}
`;
//************** Utility functions **************
window.addEventListener('resize', onWindowResize, false);
function onWindowResize() {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
gl.viewport(0, 0, canvas.width, canvas.height);
gl.uniform1f(widthHandle, window.innerWidth);
gl.uniform1f(heightHandle, window.innerHeight);
}
//Compile shader and combine with source
function compileShader(shaderSource, shaderType) {
var shader = gl.createShader(shaderType);
gl.shaderSource(shader, shaderSource);
gl.compileShader(shader);
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
throw "Shader compile failed with: " + gl.getShaderInfoLog(shader);
}
return shader;
}
//From https://codepen.io/jlfwong/pen/GqmroZ
//Utility to complain loudly if we fail to find the attribute/uniform
function getAttribLocation(program, name) {
var attributeLocation = gl.getAttribLocation(program, name);
if (attributeLocation === -1) {
throw 'Cannot find attribute ' + name + '.';
}
return attributeLocation;
}
function getUniformLocation(program, name) {
var attributeLocation = gl.getUniformLocation(program, name);
if (attributeLocation === -1) {
throw 'Cannot find uniform ' + name + '.';
}
return attributeLocation;
}
//************** Create shaders **************
//Create vertex and fragment shaders
var vertexShader = compileShader(vertexSource, gl.VERTEX_SHADER);
var fragmentShader = compileShader(fragmentSource, gl.FRAGMENT_SHADER);
//Create shader programs
var program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
gl.useProgram(program);
//Set up rectangle covering entire canvas
var vertexData = new Float32Array([-1.0, 1.0, // top left
-1.0, -1.0, // bottom left
1.0, 1.0, // top right
1.0, -1.0, // bottom right
]);
//Create vertex buffer
var vertexDataBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertexDataBuffer);
gl.bufferData(gl.ARRAY_BUFFER, vertexData, gl.STATIC_DRAW);
// Layout of our data in the vertex buffer
var positionHandle = getAttribLocation(program, 'position');
gl.enableVertexAttribArray(positionHandle);
gl.vertexAttribPointer(positionHandle,
2, // position is a vec2 (2 values per component)
gl.FLOAT, // each component is a float
false, // don't normalize values
2 * 4, // two 4 byte float components per vertex (32 bit float is 4 bytes)
0 // how many bytes inside the buffer to start from
);
//Set uniform handle
var timeHandle = getUniformLocation(program, 'time');
var widthHandle = getUniformLocation(program, 'width');
var heightHandle = getUniformLocation(program, 'height');
gl.uniform1f(widthHandle, window.innerWidth);
gl.uniform1f(heightHandle, window.innerHeight);
function draw() {
//Update time
time += dt;
//Send uniforms to program
gl.uniform1f(timeHandle, time);
//Draw a triangle strip connecting vertices 0-4
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
requestAnimationFrame(draw);
}
draw();
</script>
</html>代码分析
这段代码通过HTML、CSS和WebGL结合实现了一个“流光爱心”效果，以下是对其的详细分析。
1. HTML结构
在HTML部分，主要是一个canvas元素，它是用于绘制心形动画的区域。canvas元素通过其ID属性canvas在JavaScript中被引用，用于初始化WebGL上下文。
<canvas id="canvas" width="1400" height="600"></canvas>在这里，宽度和高度只是初始设置，代码通过JavaScript调整canvas的大小以适应浏览器窗口。
2. CSS部分
CSS的作用是设置整个网页的背景颜色为黑色，并使画布占据整个窗口，同时禁用滚动条以确保效果全屏展示。
body {
background-color: #000;
margin: 0;
overflow: hidden;
background-repeat: no-repeat;
}3. WebGL上下文初始化
JavaScript部分通过getContext('webgl')获取WebGL绘图上下文，这是一种用于在网页中绘制2D和3D图形的API。
var canvas = document.getElementById("canvas");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
var gl = canvas.getContext('webgl');
if (!gl) {
console.error("Unable to initialize WebGL.");
}这段代码确保WebGL能够正常运行，如果无法初始化WebGL，会在控制台输出错误信息。
4. 着色器程序
代码中定义了顶点着色器和片段着色器，用于处理图形的顶点和颜色计算。顶点着色器vertexSource负责定义绘制区域，而片段着色器fragmentSource则负责生成心形动画的光效。
-
顶点着色器：这个简单的顶点着色器只定义了矩形区域，覆盖整个
canvas。
attribute vec2 position;
void main() {
gl_Position = vec4(position, 0.0, 1.0);
}-
片段着色器：这是核心部分，计算并绘制了心形的流光效果。着色器使用了多种图形技术，如二次贝塞尔曲线距离函数来生成心形轮廓，
getGlow函数实现光晕效果，getHeartPosition函数计算心形轨迹。
vec2 getHeartPosition(float t){
return vec2(16.0 * sin(t) * sin(t) * sin(t),
-(13.0 * cos(t) - 5.0 * cos(2.0*t)
- 2.0 * cos(3.0*t) - cos(4.0*t)));
}这个公式是数学中的经典“心形曲线公式”，通过调整时间参数t，可以得到心形轨迹上的点。
5. 动态渲染
在draw函数中，程序使用requestAnimationFrame(draw)不断调用自己来实现帧动画，逐帧更新time变量，使得心形的流光效果随着时间变化而持续运行。
function draw() {
time += dt;
gl.uniform1f(timeHandle, time);
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
requestAnimationFrame(draw);
}每一帧，WebGL都会根据当前的时间time重新计算心形上每个点的位置，进而生成流光效果。
6. 响应窗口变化
代码监听了窗口大小的变化，使用onWindowResize函数动态调整画布的大小，确保动画始终适应窗口尺寸，并且心形保持居中显示。
window.addEventListener('resize', onWindowResize, false);
function onWindowResize() {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
gl.viewport(0, 0, canvas.width, canvas.height);
gl.uniform1f(widthHandle, window.innerWidth);
gl.uniform1f(heightHandle, window.innerHeight);
}总结
这段代码通过WebGL技术生成了一个心形流光效果。核心部分在于数学公式计算出的心形轨迹和光晕效果，通过着色器来实现。WebGL的强大之处在于它能直接操控GPU，生成高效的动画效果。
写在后面
我是一只有趣的兔子，感谢你的喜欢！