8

我想在一个立方体上使用 6 种不同的纹理,每边一个,但找不到错误。这是我当前的代码:

   var texturen = new Array();
function initTexture(sFilename,texturen)  
{
  var anz = texturen.length;
  texturen[anz] = gl.createTexture();
  texturen[anz].image = new Image();
  texturen[anz].image.onload = function()    
  {
  gl.bindTexture(gl.TEXTURE_2D, texturen[anz]);
  gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, false);
  gl.texImage2D
  (gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, texturen[anz].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);
  }
  texturen[anz].image.src = sFilename;
} 


var mvMatrix = mat4.create();
var mvMatrixStack = [];
var pMatrix = mat4.create();

function mvPushMatrix() {
    var copy = mat4.create();
    mat4.set(mvMatrix, copy);
    mvMatrixStack.push(copy);
}

function mvPopMatrix() {
    if (mvMatrixStack.length == 0) {
        throw "Invalid popMatrix!";
    }
    mvMatrix = mvMatrixStack.pop();
}


function setMatrixUniforms() {
    gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, pMatrix);
    gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, mvMatrix);
}


function degToRad(degrees) {
    return degrees * Math.PI / 180;
}

var cubeVertexPositionBuffer;
var cubeVertexTextureCoordBuffer;
var cubeVertexIndexBuffer;
var cubeVertexPositionBuffer1;
var cubeVertexTextureCoordBuffer1;
var cubeVertexIndexBuffer1;


function initBuffers() {
    cubeVertexPositionBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
    vertices = [
        // Front face
        -1.0, -1.0,  1.0,
         1.0, -1.0,  1.0,
         1.0,  1.0,  1.0,
        -1.0,  1.0,  1.0,

        // Back face
        -1.0, -1.0, -1.0,
        -1.0,  1.0, -1.0,
         1.0,  1.0, -1.0,
         1.0, -1.0, -1.0,

        // Top face
        -1.0,  1.0, -1.0,
        -1.0,  1.0,  1.0,
         1.0,  1.0,  1.0,
         1.0,  1.0, -1.0,
    ];
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
    cubeVertexPositionBuffer.itemSize = 3;
    cubeVertexPositionBuffer.numItems = 12;

cubeVertexPositionBuffer1 = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer1);
    vertices = [
       // Bottom face
        -1.0, -1.0, -1.0,
         1.0, -1.0, -1.0,
         1.0, -1.0,  1.0,
        -1.0, -1.0,  1.0,

        // Right face
         1.0, -1.0, -1.0,
         1.0,  1.0, -1.0,
         1.0,  1.0,  1.0,
         1.0, -1.0,  1.0,

        // Left face
        -1.0, -1.0, -1.0,
        -1.0, -1.0,  1.0,
        -1.0,  1.0,  1.0,
        -1.0,  1.0, -1.0,
    ];
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);
    cubeVertexPositionBuffer1.itemSize = 3;
    cubeVertexPositionBuffer1.numItems = 12;


    cubeVertexTextureCoordBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer);
    var textureCoords = [
      // Front face
      0.0, 0.0,
      1.0, 0.0,
      1.0, 1.0,
      0.0, 1.0,

      // Back face
      1.0, 0.0,
      1.0, 1.0,
      0.0, 1.0,
      0.0, 0.0,

      // Top face
      0.0, 1.0,
      0.0, 0.0,
      1.0, 0.0,
      1.0, 1.0,
    ];
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords), gl.STATIC_DRAW);
    cubeVertexTextureCoordBuffer.itemSize = 2;
    cubeVertexTextureCoordBuffer.numItems = 12;



cubeVertexTextureCoordBuffer1 = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexTextureCoordBuffer1);
    var textureCoords = [
   // Bottom face
      1.0, 1.0,
      0.0, 1.0,
      0.0, 0.0,
      1.0, 0.0,

      // Right face
      1.0, 0.0,
      1.0, 1.0,
      0.0, 1.0,
      0.0, 0.0,

      // Left face
      0.0, 0.0,
      1.0, 0.0,
      1.0, 1.0,
      0.0, 1.0,
    ];
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(textureCoords), gl.STATIC_DRAW);
    cubeVertexTextureCoordBuffer1.itemSize = 2;
    cubeVertexTextureCoordBuffer1.numItems = 12;

cubeVertexIndexBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
    var cubeVertexIndices = [
        0, 1, 2,      0, 2, 3,    // Front face
        4, 5, 6,      4, 6, 7,    // Back face
        8, 9, 10,     8, 10, 11,  // Top face
    ];
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
    cubeVertexIndexBuffer.itemSize = 1;
    cubeVertexIndexBuffer.numItems = 18;

cubeVertexIndexBuffer1 = gl.createBuffer();
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer1);
    var cubeVertexIndices = [
        12, 13, 14,   12, 14, 15, // Bottom face
        16, 17, 18,   16, 18, 19, // Right face
        20, 21, 22,   20, 22, 23  // Left face
    ];
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(cubeVertexIndices), gl.STATIC_DRAW);
    cubeVertexIndexBuffer1.itemSize = 1;
    cubeVertexIndexBuffer1.numItems = 18;



}


var xRot = 0;
var yRot = 0;
var zRot = 0;

function drawScene() {
    gl.viewport(0, 0, gl.viewportWidth, gl.viewportHeight);
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    mat4.perspective(45, gl.viewportWidth / gl.viewportHeight, 0.1, 100.0, pMatrix);

    mat4.identity(mvMatrix);

    mat4.translate(mvMatrix, [0.0, 0.0, -5.0]);

    mat4.rotate(mvMatrix, degToRad(xRot), [1, 0, 0]);
    mat4.rotate(mvMatrix, degToRad(yRot), [0, 1, 0]);
    mat4.rotate(mvMatrix, degToRad(zRot), [0, 0, 0]);
    setMatrixUniforms();

 gl.activeTexture(gl.TEXTURE0);
 gl.bindTexture(gl.TEXTURE_2D, texturen[0]); 
 gl.vertexAttribPointer
 (textureCoordAttribute, cubeVertexTextureCoordBuffer.itemSize,  gl.FLOAT, false, 0,  0);
   gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer);
  gl.vertexAttribPointer
  (shaderProgram.vertexPositionAttribute,cubeVertexPositionBuffer.itemSize, 
  gl.FLOAT, false, 0, 0);

  gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);

    gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);


 gl.activeTexture(gl.TEXTURE1);
 gl.bindTexture(gl.TEXTURE_2D, texturen[1]); 
 gl.vertexAttribPointer
 (textureCoordAttribute, cubeVertexTextureCoordBuffer1.itemSize,  gl.FLOAT, false, 0, 0);
 gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer1);
 gl.vertexAttribPointer
 (shaderProgram.vertexPositionAttribute,cubeVertexPositionBuffer1.itemSize, 
  gl.FLOAT, false, 0, 0);


    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer1);

    gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer1.numItems, gl.UNSIGNED_SHORT, 0);


}

我只是把它分成两部分,试着用两张不同的照片做一个测试。究竟什么是 cubeVertexIndexBuffers?

4

1 回答 1

16

首先,简短的回答:用以下代码替换代码的最后 10 行,我认为它应该可以工作。

gl.activeTexture(gl.TEXTURE0);
gl.bindTexture(gl.TEXTURE_2D, texturen[1]); 
gl.vertexAttribPointer(textureCoordAttribute, cubeVertexTextureCoordBuffer1.itemSize,  gl.FLOAT, false, 0, 0);
gl.bindBuffer(gl.ARRAY_BUFFER, cubeVertexPositionBuffer1);
gl.vertexAttribPointer(shaderProgram.vertexPositionAttribute,cubeVertexPositionBuffer1.itemSize, gl.FLOAT, false, 0, 0);

gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, cubeVertexIndexBuffer);
gl.drawElements(gl.TRIANGLES, cubeVertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0);

主要变化是:

  • activeTexture仍然TEXTURE0(您一次只使用一种纹理)
  • 使用cubeVertexIndexBuffer而不是cubeVertexIndexBuffer1,其中包含超出范围的索引

为了更好地解释索引的实际用途,我将向您推荐这个 SO question,因为我不想在这里重复所有这些。

现在,转向更一般的答案。

有两种基本方法可以处理在不同面上使用不同纹理的问题。第一个也是更简单的方法是完全按照您在此处所做的操作:将对象分段渲染,为每块绑定不同的纹理。虽然严格来说不是实现效果的最有效方式,但它是在游戏等高性能应用程序中处理它的最常用方式,因为它提供了很大的灵活性,尤其是当您的材质比简单的漫反射纹理更复杂时.

不过,有一种简单的方法可以在这种情况下提高像您这样的代码的性能。顶点/索引不必为每个纹理分解成单独的缓冲区。您可以将它们全部组合到一个缓冲区中,并使用不同的偏移量渲染它们,如下所示:

// On Init
var vertBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, vertBuffer);
var vertices = [
    // Vertex values for all 6 faces
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW);

var indexBuffer = gl.createBuffer();
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
var indices = [
    // Index values for all 6 faces
];
gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array(indices), gl.STATIC_DRAW);

// On Draw
// Setup the shader and uniforms and all that jazz

gl.bindBuffer(gl.ARRAY_BUFFER, vertBuffer);
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
gl.vertexAttribPointer(// Blah blah blah...);

// Draw face 0
gl.bindTexture(gl.TEXTURE_2D, texture[0]);
gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);

// Draw face 1
gl.bindTexture(gl.TEXTURE_2D, texture[1]);
gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 12);

// Draw face 2
gl.bindTexture(gl.TEXTURE_2D, texture[2]);
gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 24);

// .. And so on to face 5
// Draw face 2
gl.bindTexture(gl.TEXTURE_2D, texture[5]);
gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 60);

这里发生的情况是,每次调用drawElements只绘制 2 个三角形(6 个顶点,调用的第二个参数),但每次调用都会偏移到索引缓冲区中,以便从不同的面开始。(调用的第四个参数,表示字节偏移量。每个索引是一个 Uint16,因此每个索引 2 个字节。12 == "start on index[6]")这样所有的绑定和设置只发生一次,并且每个绘图调用只需更改实际需要的状态(纹理)。

另一种更快但更难泛化的处理方法是将纹理数组绑定到着色器制服,并使用另一个顶点属性索引到着色器中的数组。我不会详细介绍这种方法的代码,但是一旦您对 WebGL 着色器的使用感到满意,它应该相对容易设置。如果您对这种特定方法还有其他问题,最好在另一个 SO 问题中提问,以免使这个问题超载。

于 2012-07-02T20:06:18.370 回答