传统的画2d画布就是后画的会盖在先画的上面,但是在画一些三维图形时,这很难控制
深度缓冲区的作用就是区分颜色所在的层次，防止把被遮挡住的颜色显示出来。
深度缓冲很强大,用起来很简单
开启深度缓冲(测试),注意是测试
gl.enable(gl.DEPTH_TEST);
清除深度缓存
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8"/>
<title>Hidden Surface Removal & Depth Test</title>
</head>
<body>
<canvas id="canvas" width="400" height="400">
Please use a browser that supports "canvas"
</canvas>
<script id="vertex-shader" type="glsl">
attribute vec4 a_Position;
attribute vec4 a_Color;
uniform mat4 u_ProjMatrix;
uniform mat4 u_ViewMatrix;
varying vec4 v_Color;
void main() {
gl_Position = u_ProjMatrix * u_ViewMatrix * a_Position;
v_Color = a_Color;
}
</script>
<script id="fragment-shader" type="glsl">
precision mediump float;
varying vec4 v_Color;
void main() {
gl_FragColor = v_Color;
}
</script>
<script src="lib/cuon-matrix.js"></script>
<script src="lib/myutils.js"></script>
<script>
var VERTEX_SHADER_SOURCE = document.getElementById('vertex-shader').text;
var FRAGMENT_SHADER_SOURCE = document.getElementById('fragment-shader').text;
var canvas = document.getElementById("canvas");
var gl = canvas.getContext('webgl');
if (!initShaders(gl, VERTEX_SHADER_SOURCE, FRAGMENT_SHADER_SOURCE)) {
alert('Failed to init shaders');
}
var vertices = new Float32Array([
// Three triangles on the right side
0.75, 1.0, 0.0, 0.4, 0.4, 1.0, // 前面的蓝色三角形
0.25, -1.0, 0.0, 0.4, 0.4, 1.0,
1.25, -1.0, 0.0, 1.0, 0.4, 0.4,
0.75, 1.0, -2.0, 1.0, 1.0, 0.4, // 中间的黄色三角形
0.25, -1.0, -2.0, 1.0, 1.0, 0.4,
1.25, -1.0, -2.0, 1.0, 0.4, 0.4,
0.75, 1.0, -4.0, 0.4, 1.0, 0.4, // 后面的绿色三角形
0.25, -1.0, -4.0, 0.4, 1.0, 0.4,
1.25, -1.0, -4.0, 1.0, 0.4, 0.4,
// Three triangles on the left side
-0.75, 1.0, 0.0, 0.4, 0.4, 1.0, // 前面的蓝色三角形
-1.25, -1.0, 0.0, 0.4, 0.4, 1.0,
-0.25, -1.0, 0.0, 1.0, 0.4, 0.4,
-0.75, 1.0, -2.0, 1.0, 1.0, 0.4, // 中间的黄色三角形
-1.25, -1.0, -2.0, 1.0, 1.0, 0.4,
-0.25, -1.0, -2.0, 1.0, 0.4, 0.4,
-0.75, 1.0, -4.0, 0.4, 1.0, 0.4, // 后面的绿色三角形
-1.25, -1.0, -4.0, 0.4, 1.0, 0.4,
-0.25, -1.0, -4.0, 1.0, 0.4, 0.4
]);
initVertexBuffers(gl, vertices);
var u_ViewMatrix = gl.getUniformLocation(gl.program, 'u_ViewMatrix');
var u_ProjMatrix = gl.getUniformLocation(gl.program, 'u_ProjMatrix');
var viewMatrix = new Matrix4();
viewMatrix.setLookAt(0, 0, 5, 0, 0, -100, 0, 1, 0);
var projMatrix = new Matrix4();
projMatrix.setPerspective(30, canvas.width / canvas.height, 1, 100);
gl.uniformMatrix4fv(u_ViewMatrix, false, viewMatrix.elements);
gl.uniformMatrix4fv(u_ProjMatrix, false, projMatrix.elements);
//开启后,则按照z值排序
// gl.enable(gl.DEPTH_TEST);
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES, 0, 18);
function initVertexBuffers(gl, vertices) {
var vertexBuffer = gl.createBuffer();
if (!vertexBuffer) {
console.log('Failed to create buffer object');
return -1;
}
gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
var FSIZE = vertices.BYTES_PER_ELEMENT;
var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
gl.vertexAttribPointer(a_Position, 3, gl.FLOAT, false, 6 * FSIZE, 0);
gl.enableVertexAttribArray(a_Position);
var a_Color = gl.getAttribLocation(gl.program, 'a_Color');
gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, 6 * FSIZE, 3 * FSIZE);
gl.enableVertexAttribArray(a_Color);
}
</script>
</body>
</html>