永远无法弄清楚如何在 twgl 中做纹理工作

Question

这是我为 vs/fs 准备的代码和一个我想放在 canvas 上的简单立方体。篇幅省略部分内容

<script id="cube-vs" type="notjs">
    precision highhp float;
    attribute vec3 vpos;
    attribute vec3 vnormal;
    attribute vec2 vtex;
    varying vec3 fColor;
    varying vec3 fNormal;
    varying vec2 fTexCoord;

    uniform mat4 view;
    uniform mat4 proj;
    uniform mat4 model;
    uniform vec3 lightdir;
    uniform vec3 cubecolor;

    void main(void) {
        gl_Position = proj * view * model * vec4(vpos, 1.0);
        vec4 normal = normalize(model * vec4(vnormal,0.0));
        float diffuse = .2 + abs(dot(normal, vec4(lightdir,0.0)));
        fColor = (cubecolor * diffuse);
        fTexCoord = vtex;
    }
</script>
<script id="cube-fs" type="notjs">

    precision highhp float;

    varying vec3 fColor;
    varying vec3 fNormal;
    varying vec2 fTexCoord;

    uniform sampler2D texSampler;

    void main(void) {
        vec4 texColor = texture2d(texSampler, fTexCoord);
        gl_FragColor = vec4(fColor*texColor.xyz,1.0);
    }
</script>

立方体

...

    Cube.prototype.init = function(drawingState) {
        var gl=drawingState.gl;
        // create the shaders once - for all cubes
        if (!shaderProgram) {
            shaderProgram = twgl.createProgramInfo(gl, ["tree-vs", "tree-fs"]);
        }
        if (!buffers) {
            var arrays = {
                vpos : { numComponents: 3, data: [...] },
                vnormal : {numComponents:3, data: [...]},
                vtex : {numComponents:2, data: [
                    1,0,0,0,0,1,1,1,
                    1,0,0,0,0,1,1,1,
                    1,0,0,0,0,1,1,1,
                    1,0,0,0,0,1,1,1,
                    1,0,0,0,0,1,1,1,
                    1,0,0,0,0,1,1,1,
                ]},
                indices : {[...]}
                };
            buffers = twgl.createBufferInfoFromArrays(gl,arrays);
        }
        if (!texture) {
            texture = twgl.createTexture(gl, {src:textures/tree.jpg});
        }    
    };
    Cube.prototype.draw = function(drawingState) {
        var modelM = twgl.m4.scaling([this.size*1.4,this.size*1.4,this.size*1.4]);
        twgl.m4.setTranslation(modelM,this.position,modelM);
        var gl = drawingState.gl;
        gl.useProgram(shaderProgram.program);
        twgl.setBuffersAndAttributes(gl,shaderProgram,buffers);
        twgl.setUniforms(shaderProgram,{
            view:drawingState.view, proj:drawingState.proj, lightdir:drawingState.sunDirection,
            cubecolor:this.color, model: modelM, texSampler: texture);
        twgl.drawBufferInfo(gl, gl.TRIANGLES, buffers);
    };

立方体在没有纹理的情况下工作正常但是当我试着贴上纹理时，它从来没有用过我几乎尝试了所有方法，但仍然不知道如何添加纹理。那么，我怎样才能贴上纹理？

如有任何提示，我们将不胜感激。

*********编辑我已经成功上传了纹理坐标和制服但是图像没有显示出来，立方体是浅蓝色的。任何建议将不胜感激。

Answer 1

如果您能提供一个工作示例而不只是部分代码，那就太好了。上面的代码中有几个错别字。例如，在 setUniforms 部分没有结束 }。在 createTexture 部分，url 没有引号。您将 highp 拼写为 highhp，将 texture2D 拼写为 texture2d。我假设如果你说它是运行虽然没有纹理那只是转录错误因为如果不是你应该在 JavaScript 控制台中看到非常明显的错误。

不清楚哪里出了问题，但在调试 WebGL 时，我首先要做的是检查 JavaScript 控制台。是否有关于不可渲染纹理的消息？

没有？接下来我要做的就是将片段着色器更改为纯色

<script id="cube-fs" type="notjs">

    precision highhp float;

    varying vec3 fColor;
    varying vec3 fNormal;
    varying vec2 fTexCoord;

    uniform sampler2D texSampler;

    void main(void) {
        vec4 texColor = texture2d(texSampler, fTexCoord);
        gl_FragColor = vec4(fColor*texColor.xyz,1.0);
gl_FragColor = vec4(1,0,0,1);  // -------ADDED-------------------------
    }
</script>

如果您看到立方体，那么是的，问题与纹理有关。如果不是，则问题出在其他地方。

假设您看到一个红色立方体。好的，接下来是检查纹理坐标。我会将片段着色器更改为此

<script id="cube-fs" type="notjs">

    precision highhp float;

    varying vec3 fColor;
    varying vec3 fNormal;
    varying vec2 fTexCoord;

    uniform sampler2D texSampler;

    void main(void) {
        vec4 texColor = texture2d(texSampler, fTexCoord);
        gl_FragColor = vec4(fColor*texColor.xyz,1.0);
gl_FragColor = vec4(fTexCoord,0,1);  // -------CHANGED-------------------------
    }
</script>

您现在应该看到立方体带有红色->绿色阴影。否则你的纹理坐标不好。

如果看起来正确，我可能会尝试的下一件事是将着色器恢复到原来的状态，然后检查变量 texture 是否实际设置。

有很多方法可以检查这个。

使用WebGL Inspector
使用标准 JavaScript 调试器。在 setUniforms 部分放置一个断点。检查变量

做这样的事情

var uniforms = {
    view:drawingState.view, 
    proj:drawingState.proj, 
    lightdir:drawingState.sunDirection,
    cubecolor:this.color, 
    model: modelM, 
    texSampler: texture,
};
window.u = uniforms;
twgl.setUniforms(shaderProgram, uniforms);

现在打开 JavaScript 控制台并输入 u.texSampler。它应该打印类似

WebGLTexture {}

如果不是，那么可能 texture 不是您认为的变量

另一个问题是您是否经常使用 requestAnimationFrame 进行渲染，如

function render() {
  // draw stuff like maybe call someCube.draw(drawingState)
  ...
  requestAnimationFrame(render);
}
requestAnimationFrame(render);

我问是因为纹理是异步加载的，所以如果您只渲染一次，那么您将看不到任何纹理，因为它们尚未加载。

你有几个选择。

不断渲染（如上例）

twgl 将默认为 1x1 像素纹理，因此渲染应该可以进行。然后图像最终加载它会更新纹理
等待纹理加载。

如果您不想在纹理准备好之前渲染，那么您可以向 twgl.createTexture 添加一个回调，它会在纹理准备好时回调您。

另一件事是从工作样本开始

var m4 = twgl.m4;                                              // <!------------ ADDED
var v3 = twgl.v3;                                              // <!------------ ADDED

// not sure why these are globals?!???!
var shaderProgram;                                             // <!------------ ADDED
var texture;                                                   // <!------------ ADDED
var buffers;                                                   // <!------------ ADDED
var canvas = document.querySelector("canvas");                 // <!------------ ADDED
var drawingState = {                                           // <!------------ ADDED
  gl: canvas.getContext("webgl"),                              // <!------------ ADDED
  view: m4.inverse(m4.lookAt([3,3,6], [0, 0, 0], [0, 1, 0])),  // <!------------ ADDED
  proj: m4.perspective(                                        // <!------------ ADDED
    Math.PI * 0.3,                                             // <!------------ ADDED
    canvas.clientWidth / canvas.clientHeight,                  // <!------------ ADDED
    0.1, 10),                                                  // <!------------ ADDED
  sunDirection: v3.normalize([2,3,-2]),                        // <!------------ ADDED
};                                                             // <!------------ ADDED


function Cube() {            // <!-------------------------------------- ADDED
  this.size = 1;             // <!-------------------------------------- ADDED
  this.position = [0, 0, 0]; // <!-------------------------------------- ADDED 
  this.color = [1, 1, 1];    // <!-------------------------------------- ADDED
}                            // <!-------------------------------------- ADDED

Cube.prototype.init = function(drawingState) {
  var gl=drawingState.gl;
  // create the shaders once - for all cubes
  if (!shaderProgram) {
    shaderProgram = twgl.createProgramInfo(gl, ["cube-vs", "cube-fs"]);  // <!---- CHANGED
  }
  if (!buffers) {
    var arrays = {
      vpos: { numComponents: 3, data: [1, 1, -1, 1, 1, 1, 1, -1, 1, 1, -1, -1, -1, 1, 1, -1, 1, -1, -1, -1, -1, -1, -1, 1, -1, 1, 1, 1, 1, 1, 1, 1, -1, -1, 1, -1, -1, -1, -1, 1, -1, -1, 1, -1, 1, -1, -1, 1, 1, 1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, 1, -1, 1, 1, -1, 1, -1, -1, -1, -1, -1], },
      vnormal:  { numComponents: 3, data:  [1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1], },
      vtex: { numComponents: 2, data: [1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1], },
      indices:  [0, 1, 2, 0, 2, 3, 4, 5, 6, 4, 6, 7, 8, 9, 10, 8, 10, 11, 12, 13, 14, 12, 14, 15, 16, 17, 18, 16, 18, 19, 20, 21, 22, 20, 22, 23],
    };
    buffers = twgl.createBufferInfoFromArrays(gl,arrays);
  }
  if (!texture) {
    texture = twgl.createTexture(gl, {
      src: "https://farm6.staticflickr.com/5795/21506301808_efb27ed699_q_d.jpg",
      crossOrigin: "", // <!--------- not needed if on same server which "texture/tree.jpg" is
    });
  }    
};

Cube.prototype.draw = function(drawingState) {
  var modelM = twgl.m4.scaling([this.size*1.4,this.size*1.4,this.size*1.4]);
  twgl.m4.setTranslation(modelM,this.position,modelM);
  var gl = drawingState.gl;
  gl.useProgram(shaderProgram.program);
  twgl.setBuffersAndAttributes(gl,shaderProgram,buffers);
  twgl.setUniforms(shaderProgram,{
    view:drawingState.view, proj:drawingState.proj, lightdir:drawingState.sunDirection,
    cubecolor:this.color, model: modelM, texSampler: texture});
  twgl.drawBufferInfo(gl, gl.TRIANGLES, buffers);
};

var cube = new Cube();               // <!------------ ADDED
cube.init(drawingState);             // <!------------ ADDED

function render() {                  // <!------------ ADDED
  var gl = drawingState.gl           // <!------------ ADDED
  gl.enable(gl.DEPTH_TEST);          // <!------------ ADDED
  cube.draw(drawingState);           // <!------------ ADDED
  requestAnimationFrame(render);     // <!------------ ADDED
}                                    // <!------------ ADDED
requestAnimationFrame(render);       // <!------------ ADDED

canvas { border: 1px solid black; }

<script id="cube-vs" type="notjs">
    //precision highp float;    <!---------------- CHANGED
    attribute vec3 vpos;
    attribute vec3 vnormal;
    attribute vec2 vtex;
    varying vec3 fColor;
    varying vec3 fNormal;
    varying vec2 fTexCoord;

    uniform mat4 view;
    uniform mat4 proj;
    uniform mat4 model;
    uniform vec3 lightdir;
    uniform vec3 cubecolor;

    void main(void) {
        gl_Position = proj * view * model * vec4(vpos, 1.0);
        vec4 normal = normalize(model * vec4(vnormal,0.0));
        float diffuse = .2 + abs(dot(normal, vec4(lightdir,0.0)));
        fColor = (cubecolor * diffuse);
        fTexCoord = vtex;
    }
</script>
<script id="cube-fs" type="notjs">

    precision highp float;  // <!--------- CHANGED (should probably use mediump though)

    varying vec3 fColor;
    varying vec3 fNormal;
    varying vec2 fTexCoord;

    uniform sampler2D texSampler;

    void main(void) {
        vec4 texColor = texture2D(texSampler, fTexCoord);  // < !-------- CHANGED
        gl_FragColor = vec4(fColor*texColor.xyz,1.0);
    }
</script>
<canvas></canvas>
<script src="https://twgljs.org/dist/twgl-full.min.js"></script>

还有一个问题，您运行是网络服务器吗？ WebGL 需要一个网络服务器来读取纹理。请注意，运行 Web 服务器是微不足道的。 A really good one is here. Just download the version for your OS 然后

path/to/devd-download/devd path/to/project

然后去http://localhost:8000/nameOfYourHtmlFile.html

我假设这不是问题，因为如果是的话，您会在 JavaScript 控制台中看到一个关于无法加载纹理的明显错误，但您没有提到错误JavaScript 控制台

永远无法弄清楚如何在 twgl 中做纹理工作

cannot ever figure out how to do texture jobs in twgl

javascript

textures

glsl

webgl

twgl.js