我正在关注webglfundamentals博客系列和学习动画。根据我的理解，我试图以稍微不同的方式复制this，这样我就不依赖于博客系列的util文件。我无法解决此错误：
Cannot read property 'projection' of undefined
at createVertices.
var gl,
shaderProgram,
vertices;
initGL();
createShaders();
createVertices();
function initGL() {
var canvas = document.getElementById("canvas");
console.log(canvas);
gl = canvas.getContext("webgl");
gl.viewport(0, 0, canvas.width, canvas.height);
gl.clearColor(1, 1, 1, 1);
}
function createShaders() {
var vertexShader = getShader(gl, "3d-vertex-shader");
var fragmentShader = getShader(gl, "3d-fragment-shader");
shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertexShader);
gl.attachShader(shaderProgram, fragmentShader);
gl.linkProgram(shaderProgram);
}
function createVertices() {
vertices = [
// left column
0, 0, 0,
30, 0, 0,
0, 150, 0,
0, 150, 0,
30, 0, 0,
30, 150, 0,
// top rung
30, 0, 0,
100, 0, 0,
30, 30, 0,
30, 30, 0,
100, 0, 0,
100, 30, 0,
// middle rung
30, 60, 0,
67, 60, 0,
30, 90, 0,
30, 90, 0,
67, 60, 0,
67, 90, 0
];
//create buffer
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
function radToDeg(r) {
return r * 180 / Math.PI;
}
function degToRad(d) {
return d * Math.PI / 180;
}
var translation = [45, 150, 0];
var rotation = [degToRad(40), degToRad(25), degToRad(325)];
var scale = [1, 1, 1];
var color = [Math.random(), Math.random(), Math.random(), 1];
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(shaderProgram, "a_position");
// lookup uniforms
var colorLocation = gl.getUniformLocation(shaderProgram, "u_color");
var matrixLocation = gl.getUniformLocation(shaderProgram, "u_matrix");
// webglUtils.resizeCanvasToDisplaySize(gl.canvas);
// Tell it to use our program (pair of shaders)
gl.useProgram(shaderProgram);
// Turn on the attribute
gl.enableVertexAttribArray(positionLocation);
// Create a buffer to put positions in
var positionBuffer = gl.createBuffer();
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Tell the attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 3; // 3 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
positionLocation, size, type, normalize, stride, offset)
// set the color
gl.uniform4fv(colorLocation, color);
// Compute the matrices
var matrix = m4.projection(gl.canvas.clientWidth, gl.canvas.clientHeight, 400);
matrix = m4.translate(matrix, translation[0], translation[1], translation[2]);
matrix = m4.xRotate(matrix, rotation[0]);
matrix = m4.yRotate(matrix, rotation[1]);
matrix = m4.zRotate(matrix, rotation[2]);
matrix = m4.scale(matrix, scale[0], scale[1], scale[2]);
// Set the matrix.
gl.uniformMatrix4fv(matrixLocation, false, matrix);
// Draw the geometry.
var primitiveType = gl.TRIANGLES;
var offset = 0;
var count = 18; // 6 triangles in the 'F', 3 points per triangle
gl.drawArrays(primitiveType, offset, count);
}
//m4
var m4 = {
projection: function(width, height, depth) {
// Note: This matrix flips the Y axis so 0 is at the top.
return [
2 / width, 0, 0, 0,
0, -2 / height, 0, 0,
0, 0, 2 / depth, 0,
-1, 1, 0, 1,
];
},
multiply: function(a, b) {
var a00 = a[0 * 4 + 0];
var a01 = a[0 * 4 + 1];
var a02 = a[0 * 4 + 2];
var a03 = a[0 * 4 + 3];
var a10 = a[1 * 4 + 0];
var a11 = a[1 * 4 + 1];
var a12 = a[1 * 4 + 2];
var a13 = a[1 * 4 + 3];
var a20 = a[2 * 4 + 0];
var a21 = a[2 * 4 + 1];
var a22 = a[2 * 4 + 2];
var a23 = a[2 * 4 + 3];
var a30 = a[3 * 4 + 0];
var a31 = a[3 * 4 + 1];
var a32 = a[3 * 4 + 2];
var a33 = a[3 * 4 + 3];
var b00 = b[0 * 4 + 0];
var b01 = b[0 * 4 + 1];
var b02 = b[0 * 4 + 2];
var b03 = b[0 * 4 + 3];
var b10 = b[1 * 4 + 0];
var b11 = b[1 * 4 + 1];
var b12 = b[1 * 4 + 2];
var b13 = b[1 * 4 + 3];
var b20 = b[2 * 4 + 0];
var b21 = b[2 * 4 + 1];
var b22 = b[2 * 4 + 2];
var b23 = b[2 * 4 + 3];
var b30 = b[3 * 4 + 0];
var b31 = b[3 * 4 + 1];
var b32 = b[3 * 4 + 2];
var b33 = b[3 * 4 + 3];
return [
b00 * a00 + b01 * a10 + b02 * a20 + b03 * a30,
b00 * a01 + b01 * a11 + b02 * a21 + b03 * a31,
b00 * a02 + b01 * a12 + b02 * a22 + b03 * a32,
b00 * a03 + b01 * a13 + b02 * a23 + b03 * a33,
b10 * a00 + b11 * a10 + b12 * a20 + b13 * a30,
b10 * a01 + b11 * a11 + b12 * a21 + b13 * a31,
b10 * a02 + b11 * a12 + b12 * a22 + b13 * a32,
b10 * a03 + b11 * a13 + b12 * a23 + b13 * a33,
b20 * a00 + b21 * a10 + b22 * a20 + b23 * a30,
b20 * a01 + b21 * a11 + b22 * a21 + b23 * a31,
b20 * a02 + b21 * a12 + b22 * a22 + b23 * a32,
b20 * a03 + b21 * a13 + b22 * a23 + b23 * a33,
b30 * a00 + b31 * a10 + b32 * a20 + b33 * a30,
b30 * a01 + b31 * a11 + b32 * a21 + b33 * a31,
b30 * a02 + b31 * a12 + b32 * a22 + b33 * a32,
b30 * a03 + b31 * a13 + b32 * a23 + b33 * a33,
];
},
translation: function(tx, ty, tz) {
return [
1, 0, 0, 0,
0, 1, 0, 0,
0, 0, 1, 0,
tx, ty, tz, 1,
];
},
xRotation: function(angleInRadians) {
var c = Math.cos(angleInRadians);
var s = Math.sin(angleInRadians);
return [
1, 0, 0, 0,
0, c, s, 0,
0, -s, c, 0,
0, 0, 0, 1,
];
},
yRotation: function(angleInRadians) {
var c = Math.cos(angleInRadians);
var s = Math.sin(angleInRadians);
return [
c, 0, -s, 0,
0, 1, 0, 0,
s, 0, c, 0,
0, 0, 0, 1,
];
},
zRotation: function(angleInRadians) {
var c = Math.cos(angleInRadians);
var s = Math.sin(angleInRadians);
return [
c, s, 0, 0,
-s, c, 0, 0,
0, 0, 1, 0,
0, 0, 0, 1,
];
},
scaling: function(sx, sy, sz) {
return [
sx, 0, 0, 0,
0, sy, 0, 0,
0, 0, sz, 0,
0, 0, 0, 1,
];
},
translate: function(m, tx, ty, tz) {
return m4.multiply(m, m4.translation(tx, ty, tz));
},
xRotate: function(m, angleInRadians) {
return m4.multiply(m, m4.xRotation(angleInRadians));
},
yRotate: function(m, angleInRadians) {
return m4.multiply(m, m4.yRotation(angleInRadians));
},
zRotate: function(m, angleInRadians) {
return m4.multiply(m, m4.zRotation(angleInRadians));
},
scale: function(m, sx, sy, sz) {
return m4.multiply(m, m4.scaling(sx, sy, sz));
},
};
// m4 ends
/*
* https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/Tutorial/Adding_2D_content_to_a_WebGL_context
*/
function getShader(gl, id) {
var shaderScript, theSource, currentChild, shader;
shaderScript = document.getElementById(id);
if (!shaderScript) {
return null;
}
theSource = "";
currentChild = shaderScript.firstChild;
while (currentChild) {
if (currentChild.nodeType == currentChild.TEXT_NODE) {
theSource += currentChild.textContent;
}
currentChild = currentChild.nextSibling;
}
if (shaderScript.type == "x-shader/x-fragment") {
shader = gl.createShader(gl.FRAGMENT_SHADER);
} else if (shaderScript.type == "x-shader/x-vertex") {
shader = gl.createShader(gl.VERTEX_SHADER);
} else {
// Unknown shader type
return null;
}
gl.shaderSource(shader, theSource);
// Compile the shader program
gl.compileShader(shader);
// See if it compiled successfully
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
alert("An error occurred compiling the shaders: " + gl.getShaderInfoLog(shader));
return null;
}
return shader;
}<canvas id="canvas"></canvas>
<!-- vertex shader -->
<script id="3d-vertex-shader" type="x-shader/x-vertex">
attribute vec4 a_position;
uniform mat4 u_matrix;
void main() {
// Multiply the position by the matrix.
gl_Position = u_matrix * a_position;
}
</script>
<!-- fragment shader -->
<script id="3d-fragment-shader" type="x-shader/x-fragment">
precision mediump float;
uniform vec4 u_color;
void main() {
gl_FragColor = u_color;
}
</script>
<!--
for most samples webgl-utils only provides shader compiling/linking and
canvas resizing because why clutter the examples with code that's the same in every sample.
See http://webglfundamentals.org/webgl/lessons/webgl-boilerplate.html
and http://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
for webgl-utils, m3, m4, and webgl-lessons-ui.
-->
<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>
<script src="https://webglfundamentals.org/webgl/resources/webgl-lessons-ui.js"></script>
<script src="https://webglfundamentals.org/webgl/resources/webgl-lessons-helper.js"></script>
我的笔版本为here.
如果有人可以帮我解决这个错误，那将会很棒。
答案 0 :(得分：0)
错误消息
无法在createVertices读取未定义的属性'projection'。
表示尝试使用projection时未定义m4.projection。这是因为initGL();
createShaders();
createVertices();
稍后在脚本中定义。
要解决这个问题，你应该在脚本的开头做声明，最后在函数调用时做 在以下脚本中移动以下代码：
gl.drawArrays(primitiveType, offset, count);
执行此操作时，您将收到下一个错误：
GL错误：GL_INVALID_OPERATION：glDrawArrays：尝试访问属性0中超出范围的顶点
这是因为当你打电话
ARRAY_BUFFER目前的广告positionBuffer为buffer，为空。我假设您想绑定var positionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
删除以下行以解决此问题：
{{1}}