如果这个问题很愚蠢的话，我很抱歉。我遇到了最奇怪的WebGL问题。我编写了一个非常基本的WebGL程序来渲染精灵。
<!DOCTYPE html>
<html lang="en">
<head><title></title>
<style>
html, body { height: 100%; margin: 0; padding: 0; overflow: hidden; }
canvas { position: absolute; top:0;left:0; cursor: none; }
</style></head><body>
<canvas id="webgltestingthing"></canvas>
<script>
var scene,gl,cursor,sh={};
var vertexShader="\
precision mediump float;\
attribute vec2 a_position;\
attribute vec2 a_texCoord;\
uniform vec2 u_resolution;\
varying vec2 v_texCoord;\
void main() {\
gl_Position = vec4(a_position/u_resolution*2.0-1.0, 0, 1);\
v_texCoord = a_texCoord;\
}";
var fragShader="\
precision mediump float;\
uniform sampler2D u_image;\
varying vec2 v_texCoord;\
void main() {\
gl_FragColor = texture2D(u_image, v_texCoord);\
}";
function resizeScene() {
document.getElementById("webgltestingthing").width = document.body.clientWidth;
document.getElementById("webgltestingthing").height = document.body.clientHeight;
if(gl) gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight); }
mouseX=-1000; mouseY=-1000;
function trackMouse(e) { e = e || window.event; mouseX=event.pageX; mouseY=event.pageY; }
function trackMouseOut() { mouseX=-1000; mouseY=-1000; }
function createShader(gl, type, source) {
var shader = gl.createShader(type);
gl.shaderSource(shader, source);
gl.compileShader(shader);
var success = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
if (success) { return shader; }
console.log(gl.getShaderInfoLog(shader)); gl.deleteShader(shader); }
function createProgram(gl, vertexShader, fragmentShader) {
var program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);
var success = gl.getProgramParameter(program, gl.LINK_STATUS);
if (success) { return {p: program, a: {}, u: {}}; }
console.log(gl.getProgramInfoLog(program)); gl.deleteProgram(program); }
function createTexture(url,onload) {
this.img=new Image(); this.onload=onload; this.loaded=false;
this.img.src=url;
this.w=0; this.h=0; this.texture=gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, this.texture);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
postload=function() {
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, this.img);
this.loaded=true; this.onload(); }
this.img.addEventListener("load",postload.bind(this));
return this; }
function renderSprite(t,x,y) {
if(!t.loaded) return;
var x1=x,y1=scene.clientHeight-y,x2=x+t.img.width,y2=y1-t.img.height;
gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, t.texture);
gl.useProgram(sh.sprite.p);
gl.bindBuffer(gl.ARRAY_BUFFER, sh.sprite.a.texCoordBuffer);
gl.enableVertexAttribArray(sh.sprite.a.texCoord);
gl.vertexAttribPointer(sh.sprite.a.texCoord, 2, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, sh.sprite.a.positionBuffer);
gl.enableVertexAttribArray(sh.sprite.a.position);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([x1, y1, x2, y1, x1, y2, x1, y2, x2, y1, x2, y2]), gl.STATIC_DRAW);
gl.vertexAttribPointer(sh.sprite.a.position, 2, gl.FLOAT, false, 0, 0);
gl.uniform2fv(sh.sprite.u.res, [scene.clientWidth, scene.clientHeight]);
gl.uniform1i(sh.sprite.u.img, 0);
gl.drawArrays(gl.TRIANGLES, 0, 6);
}
function renderStuff() {
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
if(mouseX>0) renderSprite(cursor,mouseX,mouseY);
requestAnimationFrame(renderStuff);
}
(function() {
scene=document.getElementById("webgltestingthing"); resizeScene();
window.addEventListener('resize', resizeScene, true);
window.addEventListener('mousemove', trackMouse, true);
scene.addEventListener('mouseout', trackMouseOut, true);
gl=scene.getContext("experimental-webgl");
gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
sh.f_sprite = createShader(gl, gl.FRAGMENT_SHADER, fragShader);
sh.v_bypixels = createShader(gl, gl.VERTEX_SHADER, vertexShader);
sh.sprite = createProgram(gl, sh.v_bypixels, sh.f_sprite);
sh.sprite.u.res = gl.getUniformLocation(sh.sprite.p, "u_resolution");
sh.sprite.u.img = gl.getUniformLocation(sh.sprite.p, 'u_image');
sh.sprite.a.position = gl.getUniformLocation(sh.sprite.p, "a_position");
sh.sprite.a.positionBuffer = gl.createBuffer();
sh.sprite.a.texCoord = gl.getUniformLocation(sh.sprite.p, "a_texCoord");
sh.sprite.a.texCoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, sh.sprite.a.texCoordBuffer);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([0.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0, 1.0]), gl.STATIC_DRAW);
cursor=createTexture("graphics/cursor.png",function() { renderStuff(); });
})();
</script>
</body>
</html>
这会显示一个空白的白屏。我本希望它能在鼠标位置显示纹理。控制台中没有任何错误信息。后来我进行了一些尝试，并注意到了一些奇怪的事情，我无法解释。我将以下内容添加到我的片段着色器中：
if(v_texCoord==vec2(0.0,0.0)) gl_FragColor = vec4(1.0,0.0,0.0,1.0);
实际上，图像上每个位置的纹理坐标都是0.0/0.0！WebGL现在在精灵应该出现的位置正确地渲染出一个红色框，大小与精灵完全相同。然后我的注意力转向了设置缓冲区传递纹理坐标的部分，发生了更奇怪的事情：如果您调换代码，先设置位置缓冲区，就像这样（在rendersprite函数中）：
gl.bindBuffer(gl.ARRAY_BUFFER, sh.sprite.a.positionBuffer);
gl.enableVertexAttribArray(sh.sprite.a.position);
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([x1, y1, x2, y1, x1, y2, x1, y2, x2, y1, x2, y2]), gl.STATIC_DRAW);
gl.vertexAttribPointer(sh.sprite.a.position, 2, gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, sh.sprite.a.texCoordBuffer);
gl.enableVertexAttribArray(sh.sprite.a.texCoord);
gl.vertexAttribPointer(sh.sprite.a.texCoord, 2, gl.FLOAT, false, 0, 0);
现在我的红色框甚至都不见了！这表明我在这个简单的着色器上设置的任何缓冲区第一次都没有起作用，但我看不出任何原因。我已经尝试了各种不同的方式，并尝试了调整各种东西等，到目前为止都没有运气。我也很困惑为什么顺序有任何关系。
有人有任何想法吗？