纹理未正确映射到正方形WebGL

Question

由于某些原因，我将纹理映射到我在三维画布上绘制的框中，但它没有正确显示，我得到的只是一个蓝色框，而不是完整的纹理。

<script id="shader-fs" type="x-shader/x-fragment" type="text/javascript">
precision mediump float;
varying vec2 vTextureCoord;
uniform sampler2D uSampler;
void main(void) {
gl_FragColor = texture2D(uSampler, vec2(vTextureCoord.s, vTextureCoord.t));
}
</script>
<script id="shader-vs" type="x-shader/x-vertex" type="text/javascript">
attribute vec3 aVertexPosition;
attribute vec2 aTextureCoord;
uniform mat4 uMVMatrix;
uniform mat4 uPMatrix;
varying vec2 vTextureCoord;
void main(void) {
gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
vTextureCoord = aTextureCoord;
}
</script>

<script type="text/javascript">
var gl;
var neheTexture;
function initGL(canvas) {
try {
gl = canvas.getContext("experimental-webgl");
gl.viewportWidth = canvas.width;
gl.viewportHeight = canvas.height;
} catch (e) {
}
if (!gl) {
alert("Could not initialise WebGL, sorry :-(");
}
}
function getShader(gl, id) {
var shaderScript = document.getElementById(id);
if (!shaderScript) {
return null;
}
var str = "";
var k = shaderScript.firstChild;
while (k) {
if (k.nodeType == 3) {
str += k.textContent;
}
k = k.nextSibling;
}
var shader;
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 {
return null;
}
gl.shaderSource(shader, str);
gl.compileShader(shader);
if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
alert(gl.getShaderInfoLog(shader));
return null;
}
return shader;
}
var shaderProgram;
function initShaders() {
var fragmentShader = getShader(gl, "shader-fs");
var vertexShader = getShader(gl, "shader-vs");
shaderProgram = gl.createProgram();
gl.attachShader(shaderProgram, vertexShader);
gl.attachShader(shaderProgram, fragmentShader);
gl.linkProgram(shaderProgram);
if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
alert("Could not initialise shaders");
}
gl.useProgram(shaderProgram);
shaderProgram.vertexPositionAttribute = gl.getAttribLocation(shaderProgram, "aVertexPosition");
gl.enableVertexAttribArray(shaderProgram.vertexPositionAttribute);
shaderProgram.pMatrixUniform = gl.getUniformLocation(shaderProgram, "uPMatrix");
shaderProgram.mvMatrixUniform = gl.getUniformLocation(shaderProgram, "uMVMatrix");
}
var mvMatrix = mat4.create();
var pMatrix = mat4.create();
function setMatrixUniforms() {
gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);
}
var squareVertexPositionBuffer;
function initBuffers() {
squareVertexPositionBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
vertices = [
1.0, 1.0, 0.0,
-1.0, 1.0, 0.0,
1.0, -1.0, 0.0,
-1.0, -1.0, 0.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
squareVertexPositionBuffer.itemSize = 3;
squareVertexPositionBuffer.numItems = 4;
}
var z = -50.0;
var eye = vec3.create([0, 0, z]);  // negation of actual eye position
var pvMatrix = mat4.create();
var pvMatrixInverse = mat4.create();
function drawScene() {
var canvas = document.getElementById("MyCanvas");
var widthamount = Math.round(canvas.width/20);
var heightamount = Math.round(canvas.height / 20);

gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
mat4.perspective(90, gl.viewportWidth / gl.viewportHeight, 0.1, 3000.0, pMatrix);
mat4.identity(mvMatrix);
// calculate the view transform mvMatrix, and the projection-view matrix pvMatrix
mat4.translate(mvMatrix, eye);
mat4.multiply(pMatrix, mvMatrix, pvMatrix);
var startHeight = -((heightamount * 2.1) / 2);
var startWidth = -((widthamount * 2.1) / 2);
mat4.translate(mvMatrix, [startWidth, startHeight, 0.0]);
for (i = 0; i < heightamount; ++i) {
for (q = 0; q < widthamount; ++q) {
mat4.translate(mvMatrix, [2.1, 0.0, 0.0]);
gl.bindBuffer(gl.ARRAY_BUFFER, squareVertexPositionBuffer);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute, squareVertexPositionBuffer.itemSize, gl.FLOAT, false, 0, 0);
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, neheTexture);
gl.uniform1i(shaderProgram.samplerUniform, 0);
setMatrixUniforms();
gl.drawArrays(gl.TRIANGLE_STRIP, 0, squareVertexPositionBuffer.numItems);
}
mat4.translate(mvMatrix, [-(widthamount*2.1), 2.1, 0.0]);
}
}
function webGLStart() {
resizeCanvas();
var canvas = document.getElementById("MyCanvas");
initGL(canvas);
initShaders();
initBuffers();
initTexture();
gl.clearColor(0.0, 0.0, 0.0, 1.0);
gl.enable(gl.DEPTH_TEST);
window.addEventListener('resize', resizeCanvas, false);
tick();
}

function resizeCanvas() {
var canvas = document.getElementById("MyCanvas");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
//drawScene();
}

function handleLoadedTexture(texture) {
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, texture.image);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.bindTexture(gl.TEXTURE_2D, null);
}

function initTexture() {
neheTexture = gl.createTexture();
neheTexture.image = new Image();
neheTexture.image.onload = function () {
handleLoadedTexture(neheTexture)
}
neheTexture.image.src = "nehe.gif";
}
</script>

纹理图像看起来像完整的纹理https://github.com/gpjt/webgl-lessons/blob/master/lesson05/nehe.gif

然而，盒子变成了一个蓝色的盒子，我需要10个代表来放置图像：((

Answer 1

您没有纹理坐标。

你需要设置一个具有纹理坐标的缓冲区

squareTextureCoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, squareTextureCoordBuffer);
texcoords = [
1.0, 1.0, 
0.0, 1.0, 
1.0, 0.0, 
0.0, 0.0, 
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(texcoords), gl.STATIC_DRAW);

然后你需要查找着色器想要纹理坐标的位置

textureCoordAttribute = gl.getAttribLocation(shaderProgram, "aTextureCoord");

并设置属性

gl.enableVertexAttribArray(textureCoordAttribute);
gl.vertexAttribPointer(textureCoordAttribute, 2, gl.FLOAT, false, 0, 0);

此外，当我们在做它的时候，你可能想考虑的代码有一些小问题

1. 代码在initShaders中打开属性，但如果有多个着色器，则需要在绘图调用中打开/关闭属性

2. 代码将属性分配给WebGL对象，如shaderProgram.pMatrixUniform = ...和squareVertexPositionBuffer.itemSize = 3;，但如果您决定处理WebGLContextLost事件，则该代码将中断，因为gl.createBuffer和gl.createShader将返回null，这意味着您的代码将执行null.itemSize = 3。最好像var buffer = { id: gl.createBuffer(), itemSize: 3, ...};中那样使用WebGL制作自己的对象，这样，如果您决定处理WebGLContextLost事件，您的代码就不会中断。

3. 代码为立方体的每个面设置属性和统一。但由于它们对每个人脸都是一样的，所以在循环外设置一次不变的人脸会更有效。

4. 关于gl.viewportWidth和gl.viewportHeight的内容是半混淆的，因为它看起来viewportWidth和viewportHeight是WebGL的官方部分，尽管它们不是。最重要的是，如果你有一个缩放或改变形状的画布，它们会像在resizeCanvas中那样不同步。最好直接使用gl.canvas.width、gl.canvas.height，甚至更好地使用gl.drawBufferWidth、gl.drawingBufferHeight

5. 画布显示的大小与其分辨率是分开的。将纵横比设置为显示的大小更合适。换句话说，无论画布的分辨率如何，mat4.perspective(90, gl.canvas.clientWidth / gl.canvas.clientHeight, 0.1, 3000.0, pMatrix);都将使其以正确的纵横比进行渲染。