OpenGL---GLUT教程（八） GLUT场景漫游II

  

   GLUT 教程

            键盘例子 ------ 场景漫游 II

 

这一节里，我们再来看看上次的例子，这次我们讲使用高级的键盘控制。

 

在初始化那部分，我们有两个变量：deltaAngle和deltaMode。这些变量控制旋转和移动照相机。当为非0时，照相机执行一些动作，当为0时，照相机就不动，这两个变量的初始值是0，也就是说，照相机初始状态是不动的。

 

#include 

#include 

float angle=0.0,deltaAngle = 0.0,ratio;

float x=0.0f,y=1.75f,z=5.0f;

float lx=0.0f,ly=0.0f,lz=-1.0f;

GLint snowman_display_list;

int deltaMove = 0;

void changeSize(int w, int h)

         {

         // Prevent a divide by zero, when window is too short

         // (you cant make a window of zero width).

         if(h == 0)

                 h = 1;

         ratio = 1.0f * w / h;

         // 重置投影矩阵

         glMatrixMode(GL_PROJECTION);

         glLoadIdentity();

         // 设置视口大小。

         glViewport(0, 0, w, h);

         // 设置可视空间

         gluPerspective(45,ratio,1,1000);

         glMatrixMode(GL_MODELVIEW);

         glLoadIdentity();

         gluLookAt(x, y, z, 

                       x + lx,y + ly,z + lz,

                           0.0f,1.0f,0.0f);

         }

void drawSnowMan() {

         glColor3f(1.0f, 1.0f, 1.0f);

// Draw Body     

         glTranslatef(0.0f ,0.75f, 0.0f);

         glutSolidSphere(0.75f,20,20);

// Draw Head

         glTranslatef(0.0f, 1.0f, 0.0f);

         glutSolidSphere(0.25f,20,20);

// Draw Eyes

         glPushMatrix();

         glColor3f(0.0f,0.0f,0.0f);

         glTranslatef(0.05f, 0.10f, 0.18f);

         glutSolidSphere(0.05f,10,10);

         glTranslatef(-0.1f, 0.0f, 0.0f);

         glutSolidSphere(0.05f,10,10);

         glPopMatrix();

// Draw Nose

         glColor3f(1.0f, 0.5f , 0.5f);

         glRotatef(0.0f,1.0f, 0.0f, 0.0f);

         glutSolidCone(0.08f,0.5f,10,2);

}

GLuint createDL() {                          //返回一个显示列表

         GLuint snowManDL;

         // Create the id for the list

         snowManDL = glGenLists(1);

         // start list

         glNewList(snowManDL,GL_COMPILE);

         // call the function that contains 

         // the rendering commands

                 drawSnowMan();

         // endList

         glEndList();

         return(snowManDL);

}

void initScene() {

         glEnable(GL_DEPTH_TEST);

         snowman_display_list = createDL();

}

void orientMe(float ang) {

         lx = sin(ang);

         lz = -cos(ang);

         glLoadIdentity();

         gluLookAt(x, y, z, 

                       x + lx,y + ly,z + lz,

                           0.0f,1.0f,0.0f);

}

void moveMeFlat(int i) {

         x = x + i*(lx)*0.1;

         z = z + i*(lz)*0.1;

         glLoadIdentity();

         gluLookAt(x, y, z, 

                       x + lx,y + ly,z + lz,

                           0.0f,1.0f,0.0f);

}

下面的代码和以前的有些不同了。下面这个函数最开始，检查我们定义的那两个变量是否为0，如果不为0就调用相应的函数，来控制照相机的移动，和旋转。

void renderScene(void) {

         if (deltaMove)

                 moveMeFlat(deltaMove);

         if (deltaAngle) {

                 angle += deltaAngle;

                 orientMe(angle);

         }

         glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// Draw ground

         glColor3f(0.9f, 0.9f, 0.9f);

         glBegin(GL_QUADS);

                 glVertex3f(-100.0f, 0.0f, -100.0f);

                 glVertex3f(-100.0f, 0.0f, 100.0f);

                 glVertex3f( 100.0f, 0.0f, 100.0f);

                 glVertex3f( 100.0f, 0.0f, -100.0f);

         glEnd();

// Draw 36 SnowMen

         for(int i = -3; i < 3; i++)

                 for(int j=-3; j < 3; j++) {

                          glPushMatrix();

                          glTranslatef(i*10.0,0,j * 10.0);

                          glCallList(snowman_display_list);;

                          glPopMatrix();

                 }

         glutSwapBuffers();

}

下面的函数，分别是我们注册的特殊键控制的回调函数，和键的释放（键的松开）。

void pressKey(int key, int x, int y) {

         switch (key) {

                 case GLUT_KEY_LEFT : 

                          deltaAngle = -0.01f;break;

                 case GLUT_KEY_RIGHT : 

                          deltaAngle = 0.01f;break;

                 case GLUT_KEY_UP : 

                          deltaMove = 1;break;

                 case GLUT_KEY_DOWN : 

                          deltaMove = -1;break;

         }

}

void releaseKey(int key, int x, int y) {

         switch (key) {

                 case GLUT_KEY_LEFT : 

                 case GLUT_KEY_RIGHT : 

                          deltaAngle = 0.0f;break;

                 case GLUT_KEY_UP : 

                 case GLUT_KEY_DOWN : 

                          deltaMove = 0;break;

         }

}

Main函数里，有三行新的代码行。

glutIgnoreKeyRepeat函数，传递了一个非0值告诉GLUT不发送keyborad repeat消息，然后，glutSpecialUpFunc和glutKeyboardUpFunc调用注册的回调函数。

int main(int argc, char **argv)

{

         glutInit(&argc, argv);

         glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);

         glutInitWindowPosition(100,100);

         glutInitWindowSize(640,360);

         glutCreateWindow("SnowMen from 3D-Tech");

         initScene();

         glutIgnoreKeyRepeat(1);

         glutSpecialFunc(pressKey);

         glutSpecialUpFunc(releaseKey);

         glutDisplayFunc(renderScene);

         glutIdleFunc(renderScene);

         glutReshapeFunc(changeSize);

         glutMainLoop();

         return(0);

}

可以在这里下载这节的VC6.0工程（glut7.zip）。还可以自己改下照相机设置的函数。

 （原文地址：http://www.lighthouse3d.com/opengl/glut/index.php?8）