编写一个程序，该程序运行时可以用鼠标的一个按键调整立方体的方向，用另一个按键平移立方体，用第三个按键缩放立方体。
这是题目，我的程序不一定完全按照这个来。初学OpenGL，对那一堆坐标系表示十分混乱，慢慢看吧，有点头绪了。
（一）
1 #include2 #include 3 #define GL_PI 3.1415f 4 5 GLfloat xRot = -35.0f; 6 GLfloat yRot = 15.0f; 7 GLfloat xMov = 0.0f; 8 GLfloat winW = 0.0f; 9 GLfloat winH = 0.0f; 10 GLfloat zoom = 1.0f; 11 12 void RenderScene(void) 13 { 14 glClear(GL_COLOR_BUFFER_BIT); 15 16 glPushMatrix(); 17 glLoadIdentity(); 18 glRotatef(xRot, 1.0f, 0.0f, 0.0f); 19 glRotatef(yRot, 0.0f, 1.0f, 0.0f); 20 21 // 底面 22 glBegin(GL_LINE_LOOP); 23 glVertex3f(0.0f+xMov, 0.0f, 0.0f); 24 glVertex3f(1.0f+xMov, 0.0f, 0.0f); 25 glVertex3f(1.0f+xMov, 0.0f, 1.0f); 26 glVertex3f(0.0f+xMov, 0.0f, 1.0f); 27 glEnd(); 28 29 // 顶面 30 glBegin(GL_LINE_LOOP); 31 glVertex3f(0.0f+xMov, 1.0f, 1.0f); 32 glVertex3f(0.0f+xMov, 1.0f, 0.0f); 33 glVertex3f(1.0f+xMov, 1.0f, 0.0f); 34 glVertex3f(1.0f+xMov, 1.0f, 1.0f); 35 glEnd(); 36 37 // 背面 38 glBegin(GL_LINE_LOOP); 39 glVertex3f(0.0f+xMov, 0.0f, 0.0f); 40 glVertex3f(1.0f+xMov, 0.0f, 0.0f); 41 glVertex3f(1.0f+xMov, 1.0f, 0.0f); 42 glVertex3f(0.0f+xMov, 1.0f, 0.0f); 43 glEnd(); 44 45 // 前面 46 glBegin(GL_LINE_LOOP); 47 glVertex3f(1.0f+xMov, 0.0f, 1.0f); 48 glVertex3f(0.0f+xMov, 0.0f, 1.0f); 49 glVertex3f(0.0f+xMov, 1.0f, 1.0f); 50 glVertex3f(1.0f+xMov, 1.0f, 1.0f); 51 glEnd(); 52 53 // 右面 54 glBegin(GL_LINE_LOOP); 55 glVertex3f(1.0f+xMov, 0.0f, 0.0f); 56 glVertex3f(1.0f+xMov, 0.0f, 1.0f); 57 glVertex3f(1.0f+xMov, 1.0f, 1.0f); 58 glVertex3f(1.0f+xMov, 1.0f, 0.0f); 59 glEnd(); 60 61 // 左面 62 glBegin(GL_LINE_LOOP); 63 glVertex3f(0.0f+xMov, 0.0f, 0.0f); 64 glVertex3f(0.0f+xMov, 0.0f, 1.0f); 65 glVertex3f(0.0f+xMov, 1.0f, 1.0f); 66 glVertex3f(0.0f+xMov, 1.0f, 0.0f); 67 glEnd(); 68 69 glPopMatrix(); 70 glFlush(); 71 } 72 void OnReshape(int w, int h) 73 { 74 GLfloat aspectRatio = (GLfloat)w/(GLfloat)h; 75 winW = w; 76 winH = h; 77 78 glViewport(0,0,w,h); 79 glMatrixMode(GL_PROJECTION); 80 glLoadIdentity(); 81 if (w <= h) 82 { 83 glOrtho(-3.0f*zoom, 3.0f*zoom, -3.0f*zoom/aspectRatio, 3.0f*zoom/aspectRatio, -10.0f*zoom, 10.0f*zoom); 84 } 85 else{ 86 glOrtho(-3.0f*zoom*aspectRatio, 3.0f*zoom*aspectRatio, -3.0f*zoom, 3.0f*zoom, -10.0f*zoom, 10.0f*zoom); 87 } 88 glMatrixMode(GL_MODELVIEW); 89 glLoadIdentity(); 90 } 91 void OnMouse(int button, int state, int x, int y) 92 { 93 if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN) 94 { 95 xRot += 1; 96 yRot += 1; 97 glutPostRedisplay(); 98 } 99 else if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)100 {101 xMov -= 0.1;102 glutPostRedisplay();103 }104 else if (button == GLUT_MIDDLE_BUTTON && state == GLUT_DOWN)105 {106 zoom += 0.1;107 OnReshape(winW,winH);108 glutPostRedisplay();109 }110 }111 void OnKeyUpDown(int key, int x, int y)112 {113 if (key == GLUT_KEY_UP){114 zoom -= 0.1;115 }116 else if (key == GLUT_KEY_DOWN){117 zoom += 0.1;118 }119 OnReshape(winW,winH);120 glutPostRedisplay();121 }122 123 void SetupRC()124 {125 glClearColor(0.0f, 0.0f, 0.0f, 1.0f);126 glColor3f(0.0f, 1.0f, 0.0f);127 }128 129 void main(int argc, char **argv)130 {131 glutInit(&argc,argv);132 glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);133 glutCreateWindow("Cube");134 glutDisplayFunc(RenderScene);135 glutReshapeFunc(OnReshape);136 glutMouseFunc(OnMouse);137 glutSpecialFunc(OnKeyUpDown);138 139 SetupRC();140 141 glutMainLoop();142 }
这个程序略长，显得有点笨。手工实现了平移和放大缩小的功能，值得记录一下。
（二）
1 #include2 #include 3 #include 4 #include 5 6 GLfloat angle=0.0f; 7 GLfloat translate_x=0.0f; 8 GLfloat zoom=1.0f; 9 10 void myDisplay()11 {12 glClear (GL_COLOR_BUFFER_BIT);13 glColor3f (1.0f, 1.0f, 1.0f);14 glPushMatrix();15 {16 glMatrixMode(GL_MODELVIEW); //切换到模型视图矩阵17 glLoadIdentity();18 glRotatef(angle,1.0f,0.0f,0.0f);19 glRotatef(angle, 0.0f, 1.0f, 0.0f);20 glTranslatef(translate_x,0.0f,0.0f);21 glScalef (zoom, zoom, zoom);22 glutWireCube(1.5); //画立方体23 }24 glPopMatrix();25 glFlush();26 }27 28 void reshape(int w,int h) 29 { 30 glViewport (0, 0, (GLsizei) w, (GLsizei) h); //调整视口位置和大小31 glMatrixMode (GL_PROJECTION);//切换到投影矩阵32 glLoadIdentity();//加载单位阵至投影矩阵33 if (w <= h){34 glOrtho(-3.0f, 3.0f, -3.0f/(w/h), 3.0f/(w/h), -3.0f, 3.0f);35 }36 else{37 glOrtho(-3.0f*w/h, 3.0f*w/h, -3.0f, 3.0f, -3.0f, 3.0f);38 }39 40 glMatrixMode (GL_MODELVIEW);41 glLoadIdentity();42 }43 44 void OnMouse(int button, int state, int x, int y)45 {46 //鼠标左键47 if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)48 {49 angle += 10.0f;50 glutPostRedisplay();51 }52 //鼠标右键53 else if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)54 {55 translate_x+=0.1f;56 glutPostRedisplay();57 }58 //鼠标滚轮59 else if (state == GLUT_UP && button == GLUT_WHEEL_DOWN)60 {61 if(zoom>0)62 zoom-=0.1f;63 glutPostRedisplay();64 }65 else if(state == GLUT_UP && button == GLUT_WHEEL_UP)66 {67 zoom+=0.1f;68 glutPostRedisplay();69 }70 }71 72 73 int main(int argc, char** argv)74 {75 glutInit(&argc, argv);76 glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);77 glutInitWindowPosition(100,100);78 glutInitWindowSize(500,500); 79 glutCreateWindow("cube");80 81 glutDisplayFunc(myDisplay); 82 glutReshapeFunc(reshape);83 glutMouseFunc( OnMouse );84 glutMainLoop();85 return 0;86 }
采用了OpenGL的一些库函数实现，投影还是采用平行投影，表示对透视投影函数gluPerspective以及视点变化函数gluLookAt不是很清楚。
（三）
1 #include2 #include 3 #include 4 #include 5 6 GLfloat angle=0.0f; 7 GLfloat translate_x=0.0f; 8 GLfloat zoom=1.0f; 9 10 void myDisplay()11 {12 glClear (GL_COLOR_BUFFER_BIT);13 glColor3f (1.0f, 1.0f, 1.0f);14 glPushMatrix();15 16 glMatrixMode(GL_MODELVIEW); //切换到模型视图矩阵17 glLoadIdentity(); 18 gluLookAt (0.0f, 0.0f, 5.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f); //设置相机参数19 glRotatef(angle, 0.0f, 1.0f, 0.0f);20 glTranslatef(translate_x,0.0f,0.0f);21 glScalef (zoom, zoom, zoom);22 glutWireCube(0.5); //画立方体23 24 glPopMatrix();25 glFlush();26 }27 28 void reshape(int w,int h) 29 { 30 glViewport (0, 0, (GLsizei) w, (GLsizei) h); //调整视口位置和大小31 glMatrixMode (GL_PROJECTION);//切换到投影矩阵32 glLoadIdentity();//加载单位阵至投影矩阵33 gluPerspective(30,w/h,5,20);34 glMatrixMode (GL_MODELVIEW);35 glLoadIdentity();36 }37 38 void OnMouse(int button, int state, int x, int y)39 {40 //鼠标左键41 if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)42 {43 angle += 10.0f;44 glutPostRedisplay();45 }46 //鼠标右键47 else if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)48 {49 //xMov -= 0.1;50 translate_x+=0.1f;51 glutPostRedisplay();52 }53 //鼠标滚轮54 else if (state == GLUT_UP && button == GLUT_WHEEL_DOWN)55 {56 if(zoom>0)57 zoom-=0.1f;58 glutPostRedisplay();59 }60 else if(state == GLUT_UP && button == GLUT_WHEEL_UP)61 {62 zoom+=0.1f;63 glutPostRedisplay();64 }65 }66 67 68 int main(int argc, char** argv)69 {70 glutInit(&argc, argv);71 glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);72 glutInitWindowPosition(100,100);73 glutInitWindowSize(500,500); 74 glutCreateWindow("cube");75 76 glutDisplayFunc(myDisplay); 77 glutReshapeFunc(reshape);78 glutMouseFunc( OnMouse );79 glutMainLoop();80 return 0;81 }
用的是透视投影。我的理解是gluPerspective()和gluLookAt()要配合使用，二者中的相机位置要一致。