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上一節課我們學習了 深度緩衝-正確處理圖像的位置關係
這一節課我們將學習 深度衝突-正確處理非常貼近的圖形的顯示問題
前面我們學過了webgl繪製的順序顯示問題,本節課我們學習圖形在極度貼近的時候顯示的問題!
遇到這樣的問題怎麼處理呢 ,深度緩衝之多邊形偏移來幫你解決!
本案例運行效果:
代碼展示:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<title>webgl第36課-深度衝突-正確處理非常貼近的圖形的顯示問題</title>
</head>
<body οnlοad="main()">
<canvas id="webgl" width="400" height="400">
Please use a browser that supports "canvas"
</canvas>
<script src="../lib/webgl-utils.js"></script>
<script src="../lib/webgl-debug.js"></script>
<script src="../lib/cuon-utils.js"></script>
<script src="../lib/cuon-matrix.js"></script>
<script src="Zfighting.js"></script>
</body>
</html>
// Zfighting.js (c) 2012 matsuda
// Vertex shader program
var VSHADER_SOURCE =
'attribute vec4 a_Position;\n' +
'attribute vec4 a_Color;\n' +
'uniform mat4 u_ViewProjMatrix;\n' +
'varying vec4 v_Color;\n' +
'void main() {\n' +
' gl_Position = u_ViewProjMatrix * a_Position;\n' +
' v_Color = a_Color;\n' +
'}\n';
// Fragment shader program
var FSHADER_SOURCE =
'#ifdef GL_ES\n' +
'precision mediump float;\n' +
'#endif\n' +
'varying vec4 v_Color;\n' +
'void main() {\n' +
' gl_FragColor = v_Color;\n' +
'}\n';
function main() {
// Retrieve <canvas> element
var canvas = document.getElementById('webgl');
// Get the rendering context for WebGL
var gl = getWebGLContext(canvas);
if (!gl) {
console.log('Failed to get the rendering context for WebGL');
return;
}
// Initialize shaders
if (!initShaders(gl, VSHADER_SOURCE, FSHADER_SOURCE)) {
console.log('Failed to intialize shaders.');
return;
}
// Set the vertex coordinates and color (the blue triangle is in the front)
var n = initVertexBuffers(gl);
if (n < 0) {
console.log('Failed to set the vertex information');
return;
}
//Set clear color and enable the hidden surface removal function
gl.clearColor(0, 0, 0, 1);
gl.enable(gl.DEPTH_TEST);
// Get the storage locations of u_ViewProjMatrix
var u_ViewProjMatrix = gl.getUniformLocation(gl.program, 'u_ViewProjMatrix');
if (!u_ViewProjMatrix) {
console.log('Failed to get the storage locations of u_ViewProjMatrix');
return;
}
var viewProjMatrix = new Matrix4();
// Set the eye point, look-at point, and up vector.
viewProjMatrix.setPerspective(30, canvas.width/canvas.height, 1, 100);
viewProjMatrix.lookAt(3.06, 2.5, 10.0, 0, 0, -2, 0, 1, 0);
// Pass the view projection matrix to u_ViewProjMatrix
gl.uniformMatrix4fv(u_ViewProjMatrix, false, viewProjMatrix.elements);
// Clear color and depth buffer
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
// 啓用多邊形偏移函數
gl.enable(gl.POLYGON_OFFSET_FILL);
// Draw the triangles
gl.drawArrays(gl.TRIANGLES, 0, n/2); // 綠色三角形
gl.polygonOffset(1.0, 1.0); // 設置多邊形偏移
gl.drawArrays(gl.TRIANGLES, n/2, n/2); // 黃色三角形
}
function initVertexBuffers(gl) {
var verticesColors = new Float32Array([
// Vertex coordinates and color,這裏他們的位置是一樣的
0.0, 2.5, -5.0, 0.4, 1.0, 0.4, // The green triangle
-2.5, -2.5, -5.0, 0.4, 1.0, 0.4,
2.5, -2.5, -5.0, 1.0, 0.4, 0.4,
0.0, 3.0, -5.0, 1.0, 0.4, 0.4, // The yellow triagle
-3.0, -3.0, -5.0, 1.0, 1.0, 0.4,
3.0, -3.0, -5.0, 1.0, 1.0, 0.4,
]);
var n = 6;
// Create a buffer object
var vertexColorbuffer = gl.createBuffer();
if (!vertexColorbuffer) {
console.log('Failed to create the buffer object');
return -1;
}
// Write the vertex coordinates and color to the buffer object
gl.bindBuffer(gl.ARRAY_BUFFER, vertexColorbuffer);
gl.bufferData(gl.ARRAY_BUFFER, verticesColors, gl.STATIC_DRAW);
var FSIZE = verticesColors.BYTES_PER_ELEMENT;
// Assign the buffer object to a_Position and enable the assignment
var a_Position = gl.getAttribLocation(gl.program, 'a_Position');
if(a_Position < 0) {
console.log('Failed to get the storage location of a_Position');
return -1;
}
gl.vertexAttribPointer(a_Position, 3, gl.FLOAT, false, FSIZE * 6, 0);
gl.enableVertexAttribArray(a_Position);
// Assign the buffer object to a_Color and enable the assignment
var a_Color = gl.getAttribLocation(gl.program, 'a_Color');
if(a_Color < 0) {
console.log('Failed to get the storage location of a_Color');
return -1;
}
gl.vertexAttribPointer(a_Color, 3, gl.FLOAT, false, FSIZE * 6, FSIZE * 3);
gl.enableVertexAttribArray(a_Color);
return n;
}