webgl添加投影不显示对象
我正在看网络gl,并试图渲染一个立方体,但我有一个问题,当我尝试将投影添加到顶点着色器。我添加了一个属性,但是当我使用它来多重模型视图和位置时,它将停止显示多维数据集。我不知道为什么,想知道是否有人可以帮忙?香港专业教育学院试图寻找几个例子,但都无法得到这个工作webgl添加投影不显示对象
vertex shader
attribute vec3 aVertexPosition;
uniform mat4 uMVMatrix;
uniform mat4 uPMatrix;
void main(void) {
gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
//gl_Position = uMVMatrix * vec4(aVertexPosition, 1.0);
}
fragment shader
#ifdef GL_ES
precision highp float; // Not sure why this is required, need to google it
#endif
uniform vec4 uColor;
void main() {
gl_FragColor = uColor;
}
function init() {
// Get a reference to our drawing surface
canvas = document.getElementById("webglSurface");
gl = canvas.getContext("experimental-webgl");
/** Create our simple program **/
// Get our shaders
var v = document.getElementById("vertexShader").firstChild.nodeValue;
var f = document.getElementById("fragmentShader").firstChild.nodeValue;
// Compile vertex shader
var vs = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(vs, v);
gl.compileShader(vs);
// Compile fragment shader
var fs = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(fs, f);
gl.compileShader(fs);
// Create program and attach shaders
program = gl.createProgram();
gl.attachShader(program, vs);
gl.attachShader(program, fs);
gl.linkProgram(program);
// Some debug code to check for shader compile errors and log them to console
if (!gl.getShaderParameter(vs, gl.COMPILE_STATUS))
console.log(gl.getShaderInfoLog(vs));
if (!gl.getShaderParameter(fs, gl.COMPILE_STATUS))
console.log(gl.getShaderInfoLog(fs));
if (!gl.getProgramParameter(program, gl.LINK_STATUS))
console.log(gl.getProgramInfoLog(program));
/* Create some simple VBOs*/
// Vertices for a cube
var vertices = new Float32Array([
-0.5, 0.5, 0.5, // 0
-0.5, -0.5, 0.5, // 1
0.5, 0.5, 0.5, // 2
0.5, -0.5, 0.5, // 3
-0.5, 0.5, -0.5, // 4
-0.5, -0.5, -0.5, // 5
-0.5, 0.5, -0.5, // 6
-0.5,-0.5, -0.5 // 7
]);
// Indices of the cube
var indicies = new Int16Array([
0, 1, 2, 1, 2, 3, // front
5, 4, 6, 5, 6, 7, // back
0, 1, 5, 0, 5, 4, // left
2, 3, 6, 6, 3, 7, // right
0, 4, 2, 4, 2, 6, // top
5, 3, 1, 5, 3, 7 // bottom
]);
// create vertices object on the GPU
vbo = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vbo);
gl.bufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW);
// Create indicies object on th GPU
ibo = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, ibo);
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, indicies, gl.STATIC_DRAW);
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.enable(gl.DEPTH_TEST);
// Render scene every 33 milliseconds
setInterval(render, 33);
}
var mvMatrix = mat4.create();
var pMatrix = mat4.create();
function render() {
// Set our viewport and clear it before we render
gl.viewport(0, 0, canvas.width, canvas.height);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
gl.useProgram(program);
// Bind appropriate VBOs
gl.bindBuffer(gl.ARRAY_BUFFER, vbo);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, ibo);
// Set the color for the fragment shader
program.uColor = gl.getUniformLocation(program, "uColor");
gl.uniform4fv(program.uColor, [0.3, 0.3, 0.3, 1.0]);
//
// code.google.com/p/glmatrix/wiki/Usage
program.uPMatrix = gl.getUniformLocation(program, "uPMatrix");
program.uMVMatrix = gl.getUniformLocation(program, "uMVMatrix");
mat4.perspective(45, gl.viewportWidth/gl.viewportHeight, 1.0, 10.0, pMatrix);
mat4.identity(mvMatrix);
mat4.translate(mvMatrix, [0.0, -0.25, -1.0]);
gl.uniformMatrix4fv(program.uPMatrix, false, pMatrix);
gl.uniformMatrix4fv(program.uMVMatrix, false, mvMatrix);
// Set the position for the vertex shader
program.aVertexPosition = gl.getAttribLocation(program, "aVertexPosition");
gl.enableVertexAttribArray(program.aVertexPosition);
gl.vertexAttribPointer(program.aVertexPosition, 3, gl.FLOAT, false, 3*4, 0); // position
// Render the Object
gl.drawElements(gl.TRIANGLES, 36, gl.UNSIGNED_SHORT, 0);
}
预先感谢任何帮助
问题是在这里:
..., gl.viewportWidth/gl.viewportHeight, ...
两个gl.viewportWidth
和gl.viewportHeight
是不确定的值。
我想你错过了这两条线:
gl.viewportWidth = canvas.width;
gl.viewportHeight = canvas.height;
你会看到很多人这样做:
canvas.width = canvas.clientWidth;
canvas.height = canvas.clientHeight;
gl.viewportWidth = canvas.width;
gl.viewportHeight = canvas.height;
但请注意,WebGL的背景下也有这个两attributes :
gl.drawingBufferWidth
gl.drawingBufferHeight
谢谢胡安。我曾认为问题出现在投影部分。我改变了使用平截锥体var left = -5.0; var right = 5.0; var bottom = -5.0; var top = 5.0; var near = 1.0; var far = 20.0; var projection = mat4.create(); mat4.frustum(左,右,下,上,近,远,pMatrix); – rhunter 2012-03-24 00:17:07
糟糕的是,很快就发布了这个消息,补充一点是很好的知道为什么透视计算不能正常工作 – rhunter 2012-03-24 00:18:05
所以你的立方体显示了没有投影矩阵,正确吗?
乍一看,我认为你可能会用*面剪去几何图形。你提供了一个远*面的函数,分别为1.0和10.0。这意味着对于任何碎片都是可见的,它们必须落在[1,10]的z范围内。你的立方体每侧有1个单位,以(0,0,0)为中心,并且你正在将它从摄像机1单元“移回”。这意味着与摄像机最近的面将实际位于0.5 Z,这在裁剪范围之外并因此被丢弃。大约一半的立方体将在z> 1处,但是在那时您将看到立方体的内部。如果你打开背面剔除,你将看不到任何东西。
长话短说 - 您的立方体可能太靠近相机。试试这个:
mat4.translate(mvMatrix, [0.0, -0.25, -3.0]);
感谢Toji也看看我的代码。在Juan的修复之后,正如你所建议的那样,它离接近飞机有点近,停止了整个立方体显示 – rhunter 2012-03-24 00:27:26
考虑使用g requestAnimationFrame(http://paulirish.com/2011/requestanimationframe-for-smart-animating/) – gman 2012-03-24 18:57:43