opengl学习笔记（三）:组合变换，绘制一个简单的太阳系

创建太阳系模型

描述的程序绘制一个简单的太阳系，其中有一颗行星和一颗太阳，用同一个函数绘制。需要使用glRotate*()函数让这颗行星绕太阳旋转，并且绕自身的轴旋转。还需要使用glTranslate*()函数让这颗行星离开原点，移动到它自己的轨道上。可以在glutWireSphere()函数中使用适当的参数，在绘制球体时指定球体的大小。

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;
}

在终端gcc生成可执行程序

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

执行程序

./planet 

程序运行效果如下所示

d和D建行星自转

y和Y控制行星围绕太阳进行旋转