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| <!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<script src="https://lf26-cdn-tos.bytecdntp.com/cdn/expire-1-M/gl-matrix/3.4.2/gl-matrix.js"></script>
</head>
<body>
<canvas width="500" height="500" id="canvas"></canvas>
<script>
const canvas = document.getElementById("canvas");
const gl = canvas.getContext("webgl");
// 使用完全不透明的黑色清除所有图像
gl.clearColor(0.0, 0.0, 0.0, 1.0);
// 用上面指定的颜色清除缓冲区
gl.clear(gl.COLOR_BUFFER_BIT);
const vsSource = `
attribute vec4 a_position;
uniform mat4 u_matrix;
void main() {
// 将位置从模型空间转换到裁剪空间
gl_Position = a_position;
}
`;
const fsSource = `
precision mediump float;
uniform vec4 u_color;
void main() {
gl_FragColor = u_color;
}
`;
const vertexShader = createShader(gl, gl.VERTEX_SHADER, vsSource);
const fragmentShader = createShader(gl, gl.FRAGMENT_SHADER, fsSource);
const program = createProgram(gl, vertexShader, fragmentShader);
gl.useProgram(program);
const colorLocation = gl.getUniformLocation(program, "u_color");
gl.uniform4f(colorLocation, 1.0, 0.0, 0.0, 1.0);
const positions = [-0.5, -0.5, 0.5, -0.5, -0.5, 0.5, 0.5, 0.5];
const positionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(positions),
gl.STATIC_DRAW
);
const positionLocation = gl.getAttribLocation(program, "a_position");
gl.enableVertexAttribArray(positionLocation);
gl.vertexAttribPointer(positionLocation, 2, gl.FLOAT, false, 0, 0);
// 绘制图形
gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4);
function createShader(gl, type, fragment) {
let shader = gl.createShader(type);
gl.shaderSource(shader, fragment);
gl.compileShader(shader);
return shader;
}
function createProgram(gl, vertexShader, fragmentShader) {
const shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertexShader);
gl.attachShader(shaderProgram, fragmentShader);
gl.linkProgram(shaderProgram);
return shaderProgram;
}
</script>
</body>
</html>
|
