GLUT教程（八） GLUT情境漫遊II

 

這一節裡，我們再來看看上次的例子，這次我們講使用進階的鍵盤控制。 在初始化那部分，我們有兩個變數：deltaAngle和deltaMode。這些變數控制旋轉和移動照相機。當為非0時，照相機執行一些動作，當為0時，照相機就不動，這兩個變數的初始值是0，也就是說，照相機初始狀態是不動的。 

#include <math.h>

#include <GL/glut.h>

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;

         // 重設投影矩陣

         glMatrixMode(GL_PROJECTION);

         glLoadIdentity();

         // 設定視口大小。

         glViewport(0, 0, w, h);

         // 設定可視空間

         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() {                          //返回一個顯示列表

         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);

}

下面的代碼和以前的有些不同了。下面這個函數最開始，檢查我們定義的那兩個變數是否為0，如果不為0就調用相應的函數，來控制照相機的移動，和旋轉。

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();

}

下面的函數，分別是我們註冊的特殊鍵控制的回呼函數，和鍵的釋放（鍵的鬆開）。

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函數裡，有三行新的程式碼。

glutIgnoreKeyRepeat函數，傳遞了一個非0值告訴GLUT不發送keyborad repeat訊息，然後，glutSpecialUpFunc和glutKeyboardUpFunc調用註冊的回呼函數。

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);

}

可以在這裡下載這節的VC6.0工程（glut7.zip）。還可以自己改下照相機設定的函數。

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