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Javascript 为什么在一个简单的WebGL程序中绑定缓冲区的顺序似乎很重要？

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Javascript 为什么在一个简单的WebGL程序中绑定缓冲区的顺序似乎很重要？,javascript,webgl,Javascript,Webgl,对不起，如果这真的很愚蠢。我遇到了最奇怪的WebGL问题。我已经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: absolut

对不起，如果这真的很愚蠢。我遇到了最奇怪的WebGL问题。我已经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>
事实上，图像上的纹理坐标显然是0.0/0.0！WebGL现在在精灵应该位于的位置以精灵的精确大小正确渲染红色框。因此，我的注意力转向了我设置缓冲区以通过纹理坐标的部分，更奇怪的事情发生了：如果你交换代码，让我先设置位置缓冲区，就像这样（在rendersprite函数中）：

现在我的红盒子都不在了！因此，这向我表明，出于某种原因，我在这个简单着色器上首先设置的任何缓冲区都不起作用，但我看不出任何原因。我试过各种不同的方法，试过把事情弄得乱七八糟之类的，到目前为止运气都不好。我也不明白为什么顺序很重要

有人知道吗？

在您用来查询属性位置的设置函数中，属性不是统一的，需要使用来查询它们的位置

在属性上调用
getUniformLocation
将返回
null
，然后在
enableVertexAttributeArray
和
VertexAttributePointer
调用中将其强制转换为
0
，因此将顶点属性绑定到同一位置

sh.sprite.a.position = gl.getAttribLocation(sh.sprite.p, "a_position");
sh.sprite.a.positionBuffer = gl.createBuffer();
sh.sprite.a.texCoord = gl.getAttribLocation(sh.sprite.p, "a_texCoord");
sh.sprite.a.texCoordBuffer = gl.createBuffer();
我知道这会是一件非常愚蠢/明显的事情！谢谢，我将它标记为正确答案，因为这解决了问题。 
    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);

sh.sprite.a.position = gl.getAttribLocation(sh.sprite.p, "a_position");
sh.sprite.a.positionBuffer = gl.createBuffer();
sh.sprite.a.texCoord = gl.getAttribLocation(sh.sprite.p, "a_texCoord");
sh.sprite.a.texCoordBuffer = gl.createBuffer();