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 Screen
GLfloat 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 textures
QVector<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 Texture
glBindTexture(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 Texture
glBindTexture(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 Texture
glBindTexture(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 Mapping
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
glLightfv(GL_LIGHT1, GL_AMBIENT, LightAmbient); // Setup The Ambient Light
glLightfv(GL_LIGHT1, GL_DIFFUSE, LightDiffuse);
glLightfv(GL_LIGHT1, GL_POSITION,LightPosition); // Position The Light
glEnable(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 Buffer
glLoadIdentity(); // Reset The Current Modelview Matrix
glTranslatef(0.0f,0.0f,z); // Translate Into/Out Of The Screen By z
glRotatef(xrot,1.0f,0.0f,0.0f); // Rotate On The X Axis By xrot
glRotatef(yrot,0.0f,1.0f,0.0f); // Rotate On The Y Axis By yrot
drawObject();
xrot += xspeed; // Add xspeed To xrot
yrot += 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 TRUE light=!light; // Toggle Light TRUE/FALSE if (!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：
