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 FilteringglTexParameteri(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 ShadingglClearColor(0.0f, 0.0f, 0.0f, 0.5f);  // Black BackgroundglClearDepth(1.0f);             // Depth Buffer SetupglEnable(GL_DEPTH_TEST);        // Enables Depth TestingglDepthFunc(GL_LEQUAL);        // The Type Of Depth Test To DoglHint(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 BufferglLoadIdentity();       // Reset The Current Modelview MatrixglTranslatef(0.0f,0.0f,-5.0f);       // Move Into The Screen 5 UnitsglRotatef(xrot,1.0f,0.0f,0.0f);     // Rotate On The X AxisglRotatef(yrot,0.0f,1.0f,0.0f);   // Rotate On The Y AxisglRotatef(zrot,0.0f,0.0f,1.0f);       // Rotate On The Z AxisglBindTexture(GL_TEXTURE_2D, texture[0]);       // Select Our TexturedrawObject();xrot += 0.3f;                             // X Axis Rotationyrot += 0.2f;                             // Y Axis Rotationzrot += 0.4f;                             // Z Axis Rotation
}

实际运行效果如下所示：