我正在尝试使用webglfundamentals中的方法在webgl中渲染球体，但是在我的程序中以某种方式，球体仅被渲染为20％。在Chrome中，我收到此错误：L ERROR :GL_INVALID_OPERATION : glDrawArrays: attempt to access out of range vertices in attribute 1
var canvas;
var gl;
var index = 0;
var pointsArray = [];
var normalsArray = [];
var indexArray = [];
var colorArray = [];
var near = -10;
var far = 10;
var radius = 1.5;
var theta = 0.0;
var phi = 0.0;
var dr = 5.0 * Math.PI/180.0;
var left = -3.0;
var right = 3.0;
var ytop =3.0;
var bottom = -3.0;
var va = vec4(0.0, 0.0, -1.0,1);
var vb = vec4(0.0, 0.942809, 0.333333, 1);
var vc = vec4(-0.816497, -0.471405, 0.333333, 1);
var vd = vec4(0.816497, -0.471405, 0.333333,1);
var lightPosition = vec4(0.0, 1.0, 1.0, 0.0 );
var lightAmbient = vec4(0.2, 0.2, 0.2, 1.0 );
var lightDiffuse = vec4( 1.0, 1.0, 1.0, 1.0 );
var lightSpecular = vec4( 1.0, 1.0, 1.0, 1.0 );
var materialAmbient = vec4( 1.0, 0.0, 1.0, 1.0 );
var materialDiffuse = vec4( 1.0, 0.0, 0.0, 1.0 );
var materialSpecular = vec4( 1.0, 0.8, 0.0, 1.0 );
var materialShininess = 100.0;
var ctm;
var ambientColor, diffuseColor, specularColor;
var texture;
var modelViewMatrix, projectionMatrix;
var modelViewMatrixLoc, projectionMatrixLoc;
var eye;
var at = vec3(0.0, 0.0, 0.0);
var up = vec3(0.0, 1.0, 0.0);
var iBuffer;
function createSphereVertices(
radius,
subdivisionsAxis,
subdivisionsHeight,
opt_startLatitudeInRadians,
opt_endLatitudeInRadians,
opt_startLongitudeInRadians,
opt_endLongitudeInRadians) {
if (subdivisionsAxis <= 0 || subdivisionsHeight <= 0) {
throw Error('subdivisionAxis and subdivisionHeight must be > 0');
}
opt_startLatitudeInRadians = opt_startLatitudeInRadians || 0;
opt_endLatitudeInRadians = opt_endLatitudeInRadians || Math.PI;
opt_startLongitudeInRadians = opt_startLongitudeInRadians || 0;
opt_endLongitudeInRadians = opt_endLongitudeInRadians || (Math.PI * 2);
var latRange = opt_endLatitudeInRadians - opt_startLatitudeInRadians;
var longRange = opt_endLongitudeInRadians - opt_startLongitudeInRadians;
// We are going to generate our sphere by iterating through its
// spherical coordinates and generating 2 triangles for each quad on a
// ring of the sphere.
// var numVertices = (subdivisionsAxis + 1) * (subdivisionsHeight + 1);
var positions = [];
// var normals = webglUtils.createAugmentedTypedArray(3, numVertices);
// var texCoords = webglUtils.createAugmentedTypedArray(2 , numVertices);
// Generate the individual vertices in our vertex buffer.
for (var y = 0; y <= subdivisionsHeight; y++) {
for (var x = 0; x <= subdivisionsAxis; x++) {
// Generate a vertex based on its spherical coordinates
var u = x / subdivisionsAxis;
var v = y / subdivisionsHeight;
var theta = longRange * u;
var phi = latRange * v;
var sinTheta = Math.sin(theta);
var cosTheta = Math.cos(theta);
var sinPhi = Math.sin(phi);
var cosPhi = Math.cos(phi);
var ux = cosTheta * sinPhi;
var uy = cosPhi;
var uz = sinTheta * sinPhi;
positions.push(vec4(radius * ux, radius * uy, radius * uz,1.0));
normalsArray.push(vec4(ux, uy, uz,1.0));
// texCoords.push(1 - u, v);
}
}
var numVertsAround = subdivisionsAxis + 1;
// var indices = webglUtils.createAugmentedTypedArray(3, subdivisionsAxis * subdivisionsHeight * 2, Uint16Array);
for (var x = 0; x < subdivisionsAxis; x++) {
for (var y = 0; y < subdivisionsHeight; y++) {
// Make triangle 1 of quad.
pointsArray.push(positions[(y + 0) * numVertsAround + x]);
pointsArray.push(positions[(y + 0) * numVertsAround + x + 1]);
pointsArray.push(positions[(y + 1) * numVertsAround + x]);
// Make triangle 2 of quad.
pointsArray.push(positions[(y + 1) * numVertsAround + x]);
pointsArray.push(positions[(y + 0) * numVertsAround + x + 1]);
pointsArray.push(positions[(y + 1) * numVertsAround + x + 1]);
index +=6;
}
}
}
window.onload = function init() {
canvas = document.getElementById( "gl-canvas" );
gl = WebGLUtils.setupWebGL( canvas );
if ( !gl ) { alert( "WebGL isn't available" ); }
gl.viewport( 0, 0, canvas.width, canvas.height );
gl.clearColor( 0.0, 0.0, 0.0, 1.0 );
gl.enable(gl.DEPTH_TEST);
//
// Load shaders and initialize attribute buffers
//
var program = initShaders( gl, "vertex-shader", "fragment-shader" );
gl.useProgram( program );
createSphereVertices(1,12,12);
ambientProduct = mult(lightAmbient, materialAmbient);
diffuseProduct = mult(lightDiffuse, materialDiffuse);
specularProduct = mult(lightSpecular, materialSpecular);
var nBuffer = gl.createBuffer();
gl.bindBuffer( gl.ARRAY_BUFFER, nBuffer);
gl.bufferData( gl.ARRAY_BUFFER, flatten(normalsArray), gl.STATIC_DRAW );
var vNormal = gl.getAttribLocation( program, "vNormal" );
gl.vertexAttribPointer( vNormal, 4, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( vNormal);
var vBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vBuffer);
gl.bufferData(gl.ARRAY_BUFFER, flatten(pointsArray), gl.STATIC_DRAW);
var vPosition = gl.getAttribLocation( program, "vPosition");
gl.vertexAttribPointer(vPosition, 4, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(vPosition);
modelViewMatrixLoc = gl.getUniformLocation( program, "modelViewMatrix" );
projectionMatrixLoc = gl.getUniformLocation( program, "projectionMatrix" );
gl.uniform4fv( gl.getUniformLocation(program,
"ambientProduct"),flatten(ambientProduct) );
gl.uniform4fv( gl.getUniformLocation(program,
"diffuseProduct"),flatten(diffuseProduct) );
gl.uniform4fv( gl.getUniformLocation(program,
"specularProduct"),flatten(specularProduct) );
gl.uniform4fv( gl.getUniformLocation(program,
"lightPosition"),flatten(lightPosition) );
gl.uniform1f( gl.getUniformLocation(program,
"shininess"),materialShininess );
render();
}
function render() {
gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
eye = vec3(radius*Math.sin(theta)*Math.cos(phi),
radius*Math.sin(theta)*Math.sin(phi), radius*Math.cos(theta));
modelViewMatrix = lookAt(eye, at , up);
projectionMatrix = ortho(left, right, bottom, ytop, near, far);
gl.uniformMatrix4fv(modelViewMatrixLoc, false, flatten(modelViewMatrix) );
gl.uniformMatrix4fv(projectionMatrixLoc, false, flatten(projectionMatrix) );
for( var i=0; i<index; i+=3)
gl.drawArrays( gl.TRIANGLES, i, 3);
window.requestAnimFrame(render);
}
project1.html<!DOCTYPE html>
<html>
<script id="vertex-shader" type="x-shader/x-vertex">
attribute vec4 vPosition;
attribute vec4 vNormal;
varying vec3 N, L, E;
uniform mat4 modelViewMatrix;
uniform mat4 projectionMatrix;
uniform vec4 lightPosition;
void main()
{
vec3 pos = -(modelViewMatrix * vPosition).xyz;
vec3 light = lightPosition.xyz;
L = normalize( light - pos );
E = -pos;
N = normalize( (modelViewMatrix*vNormal).xyz);
gl_Position = projectionMatrix * modelViewMatrix * vPosition;
}
</script>
<script id="fragment-shader" type="x-shader/x-fragment">
precision mediump float;
uniform vec4 ambientProduct;
uniform vec4 diffuseProduct;
uniform vec4 specularProduct;
uniform float shininess;
varying vec3 N, L, E;
void main()
{
vec4 fColor;
vec3 H = normalize( L + E );
vec4 ambient = ambientProduct;
float Kd = max( dot(L, N), 0.0 );
vec4 diffuse = Kd*diffuseProduct;
float Ks = pow( max(dot(N, H), 0.0), shininess );
vec4 specular = Ks * specularProduct;
if( dot(L, N) < 0.0 ) specular = vec4(0.0, 0.0, 0.0, 1.0);
fColor = ambient + diffuse +specular;
fColor.a = 1.0;
gl_FragColor = fColor;
}
</script>
<script type="text/javascript" src="./Common/webgl-utils.js"></script>
<script type="text/javascript" src="./Common/initShaders.js"></script>
<script type="text/javascript" src="./Common/MV.js"></script>
<script type="text/javascript" src="project1.js"></script>
<body>
<canvas id="gl-canvas" width="512" height="512">
Oops ... your browser doesn't support the HTML5 canvas element
</canvas>
</body>
</html>这是我只得到一个未完成的领域：
最佳答案
我不知道这是实际的正确答案，因为我没有通过运行代码进行检查。
但是，我只是猜测为什么会发生此错误。
“属性变量超出范围”的主要原因
基本上，当您传递的缓冲区没有足够的长度时，就会发生这种情况。
因此，您需要检查创建的缓冲区源的数量。
您的错误是":GL_INVALID_OPERATION : glDrawArrays: attempt to access out of range vertices in attribute 1"。在这种情况下，错误消息中的attribute 1表示GLSL代码中的“ vNormal”属性。
因为它是GLSL代码中的第二个属性变量。
（如果错误代码为attribute 0，则应由vPosition产生此问题）
只要看到您的代码，我就认为长度与普通缓冲区和位置缓冲区不匹配。
代码中的表面计数：Subdivision Height * Subdivision Axis * 2
代码中的位置元素计数：Subdivision Height * Subdivision Axis *6
代码中的常规元素计数：Subdivision Height * Subdivision Axis * 4
我想这就是问题的原因。
在这种情况下，每个顶点都必须具有位置和法线，因此您的法线元素数必须为Subdivision Height * Subdivision Axis * 6
gl.vertexAttribPointer中的第二个参数
我认为您对gl.vertexAttribPointer中的第二个参数有误。
此计数意味着每个顶点需要传递多少个float元素。
在这种情况下，您为每个顶点推了3个float元素。因此，即使您在GLSL代码中使用了vec4，也需要为vPosition指定3作为参数。
通过此参数，GPU可以为每个顶点拆分这些缓冲区，并将它们并行地传递到顶点着色器。
向量中的第4个元素
这与您的问题无关，但是我发现代码可能是错误的原因。
positions.push(vec4(radius * ux, radius * uy, radius * uz,1.0));
normalsArray.push(vec4(ux, uy, uz,1.0));
您需要了解vec4中第4个元素的含义。当此向量表示坐标时，第4个元素必须为1。但是，当此向量表示方向时，第4个元素必须为0。
因为，如果这表示方向，则方向不会受到平移变换的影响。 （我建议您学习仿射变换以了解这一点）
因此，您需要像这样重写该代码。
positions.push(vec4(radius * ux, radius * uy, radius * uz,1.0));
normalsArray.push(vec4(ux, uy, uz,0));
我希望这个答案可以帮助您...
关于javascript - 为什么我的球体渲染不完整？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/34617490/