NeHe教程Qt实现——lesson06

NeHe 系列教程之六： 纹理映射

英文教程地址：lesson06

本课以第一课的代码为基础，演示了加载纹理的过程。

首先给出的是绘制几何对象和加载纹理坐标的代码

namespace {
    GLfloat     xrot = 0;             // X Rotation ( NEW )
    GLfloat     yrot = 0;             // Y Rotation ( NEW )
    GLfloat     zrot = 0;             // Z Rotation ( NEW )

    GLuint      texture[1];       // Storage For One Texture ( NEW )

    QVector<QVector3D> vertices;
    QVector<QVector2D> texCoords;

    void makeObject()
    {

        vertices<<QVector3D(-1.0f, -1.0f,  1.0f)<<QVector3D(1.0f, -1.0f,  1.0f)<<QVector3D(1.0f,  1.0f,  1.0f)<<QVector3D(-1.0f,  1.0f,  1.0f)
                <<QVector3D(-1.0f, -1.0f, -1.0f)<<QVector3D(-1.0f,  1.0f, -1.0f)<<QVector3D(1.0f,  1.0f, -1.0f)<<QVector3D(1.0f, -1.0f, -1.0f)
                <<QVector3D(-1.0f,  1.0f, -1.0f)<<QVector3D(-1.0f,  1.0f,  1.0f)<<QVector3D(1.0f,  1.0f,  1.0f)<<QVector3D(1.0f,  1.0f, -1.0f)
                <<QVector3D(-1.0f, -1.0f, -1.0f)<<QVector3D(1.0f, -1.0f, -1.0f)<<QVector3D(1.0f, -1.0f,  1.0f)<<QVector3D(-1.0f, -1.0f,  1.0f)
                <<QVector3D(1.0f, -1.0f, -1.0f)<<QVector3D(1.0f,  1.0f, -1.0f)<<QVector3D(1.0f,  1.0f,  1.0f)<<QVector3D(1.0f, -1.0f,  1.0f)
                <<QVector3D(-1.0f, -1.0f, -1.0f)<<QVector3D(-1.0f, -1.0f,  1.0f)<<QVector3D(-1.0f,  1.0f,  1.0f)<<QVector3D(-1.0f,  1.0f, -1.0f);

         texCoords<<QVector2D(0.0f, 0.0f)<<QVector2D(1.0f, 0.0f)<<QVector2D(1.0f, 1.0f)<<QVector2D(0.0f, 1.0f)
                  <<QVector2D(1.0f, 0.0f)<<QVector2D(1.0f, 1.0f)<<QVector2D(0.0f, 1.0f)<<QVector2D(0.0f, 0.0f)
                  <<QVector2D(0.0f, 1.0f)<<QVector2D(0.0f, 0.0f)<<QVector2D(1.0f, 0.0f)<<QVector2D(1.0f, 1.0f)
                  <<QVector2D(1.0f, 1.0f)<<QVector2D(0.0f, 1.0f)<<QVector2D(0.0f, 0.0f)<<QVector2D(1.0f, 0.0f)
                  <<QVector2D(1.0f, 0.0f)<<QVector2D(1.0f, 1.0f)<<QVector2D(0.0f, 1.0f)<<QVector2D(0.0f, 0.0f)
                  <<QVector2D(0.0f, 0.0f)<<QVector2D(1.0f, 0.0f)<<QVector2D(1.0f, 1.0f)<<QVector2D(0.0f, 1.0f);

          glVertexPointer(3, GL_FLOAT, 0, vertices.constData());
          glTexCoordPointer(2, GL_FLOAT, 0, texCoords.constData());

    }

    void drawObject()
    {
          glEnableClientState(GL_VERTEX_ARRAY);
          glEnableClientState(GL_TEXTURE_COORD_ARRAY);
          glDrawArrays(GL_QUADS, 0, vertices.size());
          glDisableClientState(GL_VERTEX_ARRAY);
          glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    }
}

然后是加载纹理的代码，该方法在头文件中声明：

void MyGLWidget::loadTextures()
{
    texture[0] = bindTexture(QString(":/NeHe.bmp"),
                             GL_TEXTURE_2D,
                             GL_RGBA);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); // Linear Filtering
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); // Linear Filtering
}

初始化代码：

void MyGLWidget::initializeGL()
{
    makeObject();
    loadTextures();
    glEnable(GL_TEXTURE_2D);    // Enable Texture Mapping ( NEW )

    glShadeModel(GL_SMOOTH);   // Enables Smooth Shading
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);  // Black Background
    glClearDepth(1.0f);             // Depth Buffer Setup
    glEnable(GL_DEPTH_TEST);        // Enables Depth Testing
    glDepthFunc(GL_LEQUAL);        // The Type Of Depth Test To Do
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); // Really Nice Perspective Calculations
}

最后，是实际的绘制代码：

void MyGLWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  // Clear The Screen And The Depth Buffer
    glLoadIdentity();       // Reset The Current Modelview Matrix
    glTranslatef(0.0f,0.0f,-5.0f);       // Move Into The Screen 5 Units

    glRotatef(xrot,1.0f,0.0f,0.0f);     // Rotate On The X Axis
    glRotatef(yrot,0.0f,1.0f,0.0f);   // Rotate On The Y Axis
    glRotatef(zrot,0.0f,0.0f,1.0f);       // Rotate On The Z Axis

    glBindTexture(GL_TEXTURE_2D, texture[0]);       // Select Our Texture
    drawObject();

    xrot += 0.3f;                             // X Axis Rotation
    yrot += 0.2f;                             // Y Axis Rotation
    zrot += 0.4f;                             // Z Axis Rotation
}

实际运行效果如下所示：