opengl學習筆記（五）:組合變換，繪制一個簡單的太陽系

創建太陽系模型

描述的程序繪制一個簡單的太陽系，其中有一顆行星和一顆太陽，用同一個函數繪制。需要使用glRotate*()函數讓這顆行星繞太陽旋轉，並且繞自身的軸旋轉。還需要使用glTranslate*()函數讓這顆行星離開原點，移動到它自己的軌道上。可以在glutWireSphere()函數中使用適當的參數，在繪制球體時指定球體的大小。

planet.c

#include <GL/glut.h>

static int year =0,day =0;

void init(void)
{
    glClearColor(0.0,0.0,0.0,0.0);
    glShadeModel(GL_FLAT);
}

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0,1.0,1.0);
    glPushMatrix();
    glutSolidSphere(1.0,20,16);
    glRotatef((GLfloat)year,0.0,1.0,0.0);
    glTranslatef(2.0,0.0,0.0);
    glRotatef((GLfloat)day,0.0,1.0,0.0);
    glutSolidSphere(0.2,10,8);
    glPopMatrix();
    glutSwapBuffers();
}

void reshape(int w, int h)
{
    glViewport(0,0,(GLsizei)w,(GLsizei)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(60.0,(GLfloat)w/(GLfloat)h,1.0,20.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(0.0,0.0,5.0,0.0,0.0,0.0,0.0,1.0,0.0);
}

void keyboard(unsigned char key, int x, int y)
{
    switch (key){
        case 'd':
        day =(day + 10)%360;
        glutPostRedisplay();
        break;
        case 'D':
        day =(day - 10)%360;
        glutPostRedisplay();
        break;
        case 'y':
        year =(year + 5 )%360;
        glutPostRedisplay();
        break;
        case 'Y':
        year =(year - 5)%360;
        glutPostRedisplay();
        break;
        default:
        break;

    }

}

int main(int argc, char** argv)
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(500,500);
    glutInitWindowPosition(100,100);
    glutCreateWindow(argv[0]);
    init();
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutKeyboardFunc(keyboard);
    glutMainLoop();
    return 0;
}

在終端gcc生成可執行程序

gcc planet.c -o planet -lGL -lGLU -lglut

執行程序

./planet 

程序運行效果如下所示

d和D建行星自轉

y和Y控制行星圍繞太陽進行旋轉