NeHe 系列教程之七： 光照及纹理过滤

英文教程地址：lesson07

本课将以第一课的代码为基础， 实现光照效果。

首先是对象定义与纹理加载的代码：

namespace {
bool    light;                       // Lighting ON / OFF
bool    lp;                         // L Pressed?
bool    fp;                         // F Pressed?
GLfloat xrot;                       // X Rotation
GLfloat yrot;                       // Y Rotation
GLfloat xspeed;                     // X Rotation Speed
GLfloat yspeed;                     // Y Rotation Speed
GLfloat z=-5.0f;                    // Depth Into The ScreenGLfloat LightAmbient[]= { 0.5f, 0.5f, 0.5f, 1.0f };             // Ambient Light Values ( NEW )
GLfloat LightDiffuse[]= { 1.0f, 1.0f, 1.0f, 1.0f };              // Diffuse Light Values ( NEW )
GLfloat LightPosition[]= { 0.0f, 0.0f, 2.0f, 1.0f };            // Light Position ( NEW )
GLuint  filter;                                 // Which Filter To Use
GLuint  texture[3];                             // Storage for 3 texturesQVector<QVector3D> vertices;
QVector<QVector2D> texCoords;
QVector<QVector3D> normals;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);normals<<QVector3D(0.0f, 0.0f, 1.0f)<<QVector3D(0.0f, 0.0f, 1.0f)<<QVector3D(0.0f, 0.0f, 1.0f)<<QVector3D(0.0f, 0.0f, 1.0f)<<QVector3D(0.0f, 0.0f,-1.0f)<<QVector3D(0.0f, 0.0f,-1.0f)<<QVector3D(0.0f, 0.0f,-1.0f)<<QVector3D(0.0f, 0.0f,-1.0f)<<QVector3D(0.0f, 1.0f, 0.0f)<<QVector3D(0.0f, 1.0f, 0.0f)<<QVector3D(0.0f, 1.0f, 0.0f)<<QVector3D(0.0f, 1.0f, 0.0f)<<QVector3D(0.0f, -1.0f, 0.0f)<<QVector3D(0.0f, -1.0f, 0.0f)<<QVector3D(0.0f, -1.0f, 0.0f)<<QVector3D(0.0f, -1.0f, 0.0f)<<QVector3D(1.0f, 0.0f, 0.0f)<<QVector3D(1.0f, 0.0f, 0.0f)<<QVector3D(1.0f, 0.0f, 0.0f)<<QVector3D(1.0f, 0.0f, 0.0f)<<QVector3D(-1.0f, 0.0f, 0.0f)<<QVector3D(-1.0f, 0.0f, 0.0f)<<QVector3D(-1.0f, 0.0f, 0.0f)<<QVector3D(-1.0f, 0.0f, 0.0f);glVertexPointer(3, GL_FLOAT, 0, vertices.constData());glTexCoordPointer(2, GL_FLOAT, 0, texCoords.constData());glNormalPointer(GL_FLOAT, 0, normals.constData());}void drawObject()
{glEnableClientState(GL_VERTEX_ARRAY);glEnableClientState(GL_TEXTURE_COORD_ARRAY);glEnableClientState(GL_NORMAL_ARRAY);glBindTexture(GL_TEXTURE_2D, texture[filter]);glDrawArrays(GL_QUADS, 0, vertices.size());glDisableClientState(GL_VERTEX_ARRAY);glDisableClientState(GL_TEXTURE_COORD_ARRAY);glDisableClientState(GL_NORMAL_ARRAY);
}
}

加载纹理的代码如下, 采用了三种不同的纹理过滤方式：

  void MyGLWidget::loadTextures()
{QImage image;if (image.load(":/Crate.bmp")) {image =  convertToGLFormat(image);glGenTextures(3, texture);// Create Nearest Filtered TextureglBindTexture(GL_TEXTURE_2D, texture[0]);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image.width(), image.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, image.bits());// Create Linear Filtered TextureglBindTexture(GL_TEXTURE_2D, texture[1]);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image.width(), image.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, image.bits());// Create MipMapped TextureglBindTexture(GL_TEXTURE_2D, texture[2]);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_NEAREST);gluBuild2DMipmaps(GL_TEXTURE_2D, GL_RGBA, image.width(), image.height(), GL_RGBA, GL_UNSIGNED_BYTE, image.bits());}
}

接着是OpenGL 初始函数，启用了光照效果

void MyGLWidget::initializeGL()
{makeObject();loadTextures();glEnable(GL_TEXTURE_2D);    // Enable Texture MappingglShadeModel(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 CalculationsglLightfv(GL_LIGHT1, GL_AMBIENT, LightAmbient);             // Setup The Ambient LightglLightfv(GL_LIGHT1, GL_DIFFUSE, LightDiffuse);glLightfv(GL_LIGHT1, GL_POSITION,LightPosition);            // Position The LightglEnable(GL_LIGHT1);                            // Enable Light One
}

绘制函数如下：

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,z);                      // Translate Into/Out Of The Screen By zglRotatef(xrot,1.0f,0.0f,0.0f);                     // Rotate On The X Axis By xrotglRotatef(yrot,0.0f,1.0f,0.0f);                     // Rotate On The Y Axis By yrotdrawObject();xrot += xspeed;                        // Add xspeed To xrotyrot += yspeed;                       // Add yspeed To yrot
}

最后按键处理，主要是开启和关闭光照，以及切换不同的纹理过滤方式：

void MyGLWidget::keyReleaseEvent(QKeyEvent *e)
{switch (e->key()) {case Qt::Key_L:lp = false;break;case Qt::Key_I:fp = false;break;default:QGLWidget::keyReleaseEvent(e);}
}

void MyGLWidget::keyPressEvent(QKeyEvent *e)
{switch (e->key()) {case Qt::Key_I:fp = true;filter += 1;if (filter > 2)filter = 0;break;case Qt::Key_F:fullscreen = !fullscreen;if (fullscreen) {showFullScreen();} else {resize(640, 480);showNormal();}break;case Qt::Key_L:if (!lp) {lp=true;                // lp Becomes TRUElight=!light;               // Toggle Light TRUE/FALSEif (!light)             // If Not Light{glDisable(GL_LIGHTING);     // Disable Lighting}else                    // Otherwise{glEnable(GL_LIGHTING);      // Enable Lighting}}break;case Qt::Key_PageUp:z -= 0.02f;break;case Qt::Key_PageDown:z += 0.02f;break;case Qt::Key_Up:xspeed -= 0.01f;break;case Qt::Key_Down:xspeed += 0.01f;break;case Qt::Key_Right:yspeed += 0.01f;break;case Qt::Key_Left:yspeed -= 0.01f;break;case Qt::Key_Escape:QMessageBox::StandardButton reply;reply = QMessageBox::question(NULL, "NeHe","Do you want to exit?",QMessageBox::Yes | QMessageBox::No,QMessageBox::Yes);if (reply == QMessageBox::Yes) {qApp->quit();}break;default:QGLWidget::keyPressEvent(e);break;}
}

运行效果图如下所示：