webgl第36课-深度冲突-正确处理非常贴近的图形的显示问题 - 好文

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上一节课我们学习了深度缓冲-正确处理图像的位置关系

这一节课我们将学习深度冲突-正确处理非常贴近的图形的显示问题

前面我们学过了webgl绘制的顺序显示问题，本节课我们学习图形在极度贴近的时候显示的问题！

遇到这样的问题怎么处理呢，深度缓冲之多边形偏移来帮你解决！

本案例运行效果：

代码展示：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8" />
<title>webgl第36课-深度冲突-正确处理非常贴近的图形的显示问题</title> </head> <body onload="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); //
启用多边形偏移函数 gl.enable(gl.POLYGON_OFFSET_FILL); // Draw the triangles
gl.drawArrays(gl.TRIANGLES, 0, n/2); // 绿色三角形 gl.polygonOffset(1.0, 1.0); //
设置多边形偏移 gl.drawArrays(gl.TRIANGLES, n/2, n/2); // 黄色三角形 } function
initVertexBuffers(gl) { var verticesColors = new Float32Array([ // Vertex
coordinates and color，这里他们的位置是一样的 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; }

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