OpenGL ES - 纹理映射8个顶点立方体的所有面？

Question

使用Android模拟器完成一些OpenGL-ES教程.我已经完成了纹理映射,并且在映射到多维数据集时遇到了一些麻烦.是否可以将纹理映射到具有8个顶点和12个三角形的立方体的所有面,如下所述？

// Use half as we are going for a 0,0,0 centre.
    width  /= 2;
    height /= 2;
    depth  /= 2;

    float vertices[] = { -width, -height, depth, // 0
                          width, -height, depth, // 1
                          width,  height, depth, // 2
                         -width,  height, depth, // 3
                         -width, -height, -depth, // 4
                          width, -height, -depth, // 5
                          width,  height, -depth, // 6
                         -width,  height, -depth, // 7
    };

    short indices[] = { 
            // Front
            0,1,2,
            0,2,3,
            // Back
            5,4,7,
            5,7,6,
            // Left
            4,0,3,
            4,3,7,
            // Right
            1,5,6,
            1,6,2,
            // Top
            3,2,6,
            3,6,7,
            // Bottom
            4,5,1,
            4,1,0,
    };

   float texCoords[] = {
        1.0f, 1.0f,
        0.0f, 1.0f,
        0.0f, 0.0f,
        1.0f, 0.0f,

        1.0f, 1.0f,
        0.0f, 1.0f,
        0.0f, 0.0f,
        1.0f, 0.0f,

        1.0f, 1.0f,
        0.0f, 1.0f,
        0.0f, 0.0f,
        1.0f, 0.0f,

        1.0f, 1.0f,
        0.0f, 1.0f,
        0.0f, 0.0f,
        1.0f, 0.0f,

        1.0f, 1.0f,
        0.0f, 1.0f,
        0.0f, 0.0f,
        1.0f, 0.0f,

        1.0f, 1.0f,
        0.0f, 1.0f,
        0.0f, 0.0f,
        1.0f, 0.0f,
    };

我已经让正面和背面正常工作,但是,没有其他面部显示纹理.

alt text http://www.freeimagehosting.net/uploads/60d292613d.jpg

绘图代码

public void draw(GL10 gl) {
    // Counter-clockwise winding.
    gl.glFrontFace(GL10.GL_CCW);

    // Enable face culling.
    gl.glEnable(GL10.GL_CULL_FACE);

    // What faces to remove with the face culling.
    gl.glCullFace(GL10.GL_BACK);

    // Enabled the vertices buffer for writing and to be used during
    // rendering.
    gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);

    // Specifies the location and data format of an array of vertex
    // coordinates to use when rendering.
    gl.glVertexPointer(3, GL10.GL_FLOAT, 0, verticesBuffer);

    if (normalsBuffer != null) {
        // Enabled the normal buffer for writing and to be used during rendering.
        gl.glEnableClientState(GL10.GL_NORMAL_ARRAY);

        // Specifies the location and data format of an array of normals to use when rendering.
        gl.glNormalPointer(GL10.GL_FLOAT, 0, normalsBuffer);
    }

    // Set flat color
    gl.glColor4f(rgba[0], rgba[1], rgba[2], rgba[3]);

    // Smooth color
    if ( colorBuffer != null ) {
        // Enable the color array buffer to be used during rendering.
        gl.glEnableClientState(GL10.GL_COLOR_ARRAY);
        // Point out the where the color buffer is.
        gl.glColorPointer(4, GL10.GL_FLOAT, 0, colorBuffer);
    }

    // Use textures?
    if ( textureBuffer != null) {
        gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY);
        gl.glEnable(GL10.GL_TEXTURE_2D);
        gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer);
    }

    // Translation and rotation before drawing
    gl.glTranslatef(x, y, z);
    gl.glRotatef(rx, 1, 0, 0);
    gl.glRotatef(ry, 0, 1, 0);
    gl.glRotatef(rz, 0, 0, 1);

    gl.glDrawElements(GL10.GL_TRIANGLES, numOfIndices, GL10.GL_UNSIGNED_SHORT, indicesBuffer);

    // Disable the vertices buffer.
    gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
    gl.glDisableClientState(GL10.GL_COLOR_ARRAY);
    gl.glDisableClientState(GL10.GL_NORMAL_ARRAY);
    gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY);

    // Disable face culling.
    gl.glDisable(GL10.GL_CULL_FACE);
}

Answer 1

你必须使用24个顶点.在OpenGL中,顶点不仅仅是位置,它是所有顶点属性的集合.使用相同的索引访问每个顶点数组.

臭名昭着的立方体示例几乎每个人都认为在开始使用OpenGL时效率低下,但在现实世界中,更复杂的模型中,重复程度非常低.