C 以椭圆路径旋转地球：OpenGL

我需要在OpenGL中使地球围绕太阳旋转。我现在已经能够绕太阳旋转了，但是我需要在椭圆轨道上旋转它。现在椭圆已经产生了，但我不知道如何沿着椭圆旋转

绘制功能类似于：

    //orbit
    glColor3f(1,1,1); 
    drawEllipse(3.2f,1.0f); //draws ellipse 
    //sun
    glTranslatef(0,0,0);//suns position
    glColor3d(1,1,0);
    glutSolidSphere(2,50,50);

    //EARTH
    glRotatef(angle,0.0f,1.0f,0.0f);
    glTranslatef(6.0f,0.0f,0.0f);//postion earths


    glPushMatrix();
    glRotatef(angle2, 0.0f,1.0f,0.0f);
    glColor3d(0.5,0.8,1);

    glutSolidSphere(1,50,50);
    glPopMatrix();

这样您可以在椭圆上的每个点绘制球体。

定义两个跟踪（x，y）坐标的变量，用于沿椭圆平移地球

float xForEarth, yForEarth;

以及计数度数的计数器（从0到360，然后再到0）

并使用以下代码（在绘图方法中）制作椭圆并在其上绘制地球：

glBegin(GL_POINTS);
    for (int i=0; i < 360; i++) 
    { 
        float degInRad = i*DEG2RAD; //const float DEG2RAD = 3.14159/180.0;
        glVertex3f(cos(degInRad)*6.0, 
            sin(degInRad)*2.3,0.0f);
    }
    glEnd();
    if(counterForEarth>359)
        counterForEarth = 0;//reset to 0 when becomes 360
    else
        counterForEarth++;//this will control the speed. Do counterForEarth += 2 to increase it's speed and vice-versa

    xForEarth = cos(counterForEarth*DEG2RAD)*6.0f;//to change the x co-ordinate
    yForEarth = sin(counterForEarth*DEG2RAD)*2.3f;//to change the y co-ordinate
    glPushMatrix();
    glTranslatef(xForEarth,yForEarth,0.0f);
    glRotatef(angle,0.0f,1.0f,0.0f);
    glutSolidSphere(.4,30,30);//draw Earth
    glPopMatrix();

glBegin（GL_点）；
对于（int i=0；i<360；i++）
{ 
float degInRad=i*DEG2RAD；//常数float DEG2RAD=3.14159/180.0；
glVertex3f（cos（degInRad）*6.0，
sin（degInRad）*2.3,0.0f；
}
格伦德（）；
如果（反地球>359）
反地球=0//变为360时重置为0
其他的
反地球++//这将控制速度。做反地球+=2来增加它的速度，反之亦然
xForEarth=cos（对地*DEG2RAD）*6.0f//更改x坐标的步骤
yForEarth=sin（对地*DEG2RAD）*2.3f//更改y坐标的步骤
glPushMatrix（）；
glTranslatef（xForEarth，yForEarth，0.0f）；
glRotatef（角度，0.0f，1.0f，0.0f）；
固体球（.4,30,30）//拔土
glPopMatrix（）；

您将需要参数化以获得地球在每个时间步的目标位置。秒，您不能简单地使用旋转+平移来获得椭圆上的正确位置。试着看看这个：

int counterForEarth = 0;

glBegin(GL_POINTS);
    for (int i=0; i < 360; i++) 
    { 
        float degInRad = i*DEG2RAD; //const float DEG2RAD = 3.14159/180.0;
        glVertex3f(cos(degInRad)*6.0, 
            sin(degInRad)*2.3,0.0f);
    }
    glEnd();
    if(counterForEarth>359)
        counterForEarth = 0;//reset to 0 when becomes 360
    else
        counterForEarth++;//this will control the speed. Do counterForEarth += 2 to increase it's speed and vice-versa

    xForEarth = cos(counterForEarth*DEG2RAD)*6.0f;//to change the x co-ordinate
    yForEarth = sin(counterForEarth*DEG2RAD)*2.3f;//to change the y co-ordinate
    glPushMatrix();
    glTranslatef(xForEarth,yForEarth,0.0f);
    glRotatef(angle,0.0f,1.0f,0.0f);
    glutSolidSphere(.4,30,30);//draw Earth
    glPopMatrix();