使用 opengl 进行 2D 轨道移动

问题描述

你好，我正试图在一条轨道路径上绕太阳运行地球。到目前为止，我所做的绘制了两个圆，一个是太阳，另一个是地球。地球在椭圆上。尝试使用 glutTimerFunc() 创建一个动画但没有结果，这是代码。如何以椭圆路径使地球绕太阳运行。

#include <gl/glut.h>
#include <math.h>
#define PI 3.14159
#define circlePoints 256
#define ellipsePoints 256 
int i;

/*void myWireSphere(GLfloat radius,int slices,int stacks) {
  glPushmatrix();
  glrotatef(-90.0,1.0,0.0,0.0);
  glutWireSphere(radius,slices,stacks);
  glPopMatrix();
}*/
void circle(){
        glColor3f(1,1,0);
        GLfloat angleStep=2*PI/(float)circlePoints;
    gluint pointsPerQuarter=circlePoints/4;
    GLfloat x[circlePoints];
    GLfloat y[circlePoints];
    GLfloat radius=3;
    for(i=0;i<pointsPerQuarter/2;i++)
    {
        //Define points in first quadrant
        x[i]=radius*cos(i*angleStep);
        y[i]=radius*sin(i*angleStep);
        x[pointsPerQuarter-1-i]=y[i];
        y[pointsPerQuarter-1-i]=x[i];
        //Define points in second quadrant
        x[pointsPerQuarter+i]=-y[i];
        y[pointsPerQuarter+i]=x[i];
        x[2*pointsPerQuarter-1-i]=-x[i];
        y[2*pointsPerQuarter-1-i]=y[i];
        //Define points in third quadrant
        x[2*pointsPerQuarter+i]=-x[i];
        y[2*pointsPerQuarter+i]=-y[i];
        x[3*pointsPerQuarter-1-i]=-y[i];
        y[3*pointsPerQuarter-1-i]=-x[i];
        //Define points in fourth quadrant
        x[3*pointsPerQuarter+i]=y[i];
        y[3*pointsPerQuarter+i]=-x[i];
        x[4*pointsPerQuarter-1-i]=x[i];
        y[4*pointsPerQuarter-1-i]=-y[i]; 
    }
    
    glBegin(GL_LINE_LOOP);
    for (i=0;i<circlePoints;i++)
    {
        glVertex2f(x[i],y[i]);
    }
    glEnd();
    
}
void circlearth(){
        glColor3f(0,1);
        GLfloat angleStep=2*PI/(float)circlePoints;
    gluint pointsPerQuarter=circlePoints/4;
    GLfloat x[circlePoints];
    GLfloat y[circlePoints];
    GLfloat radius=1;
    for(i=0;i<pointsPerQuarter/2;i++)
    {
        //Define points in first quadrant
        x[i]=radius*cos(i*angleStep);
        y[i]=radius*sin(i*angleStep);
        x[pointsPerQuarter-1-i]=y[i];
        y[pointsPerQuarter-1-i]=x[i];
        //Define points in second quadrant
        x[pointsPerQuarter+i]=-y[i];
        y[pointsPerQuarter+i]=x[i];
        x[2*pointsPerQuarter-1-i]=-x[i];
        y[2*pointsPerQuarter-1-i]=y[i];
        //Define points in third quadrant
        x[2*pointsPerQuarter+i]=-x[i];
        y[2*pointsPerQuarter+i]=-y[i];
        x[3*pointsPerQuarter-1-i]=-y[i];
        y[3*pointsPerQuarter-1-i]=-x[i];
        //Define points in fourth quadrant
        x[3*pointsPerQuarter+i]=y[i];
        y[3*pointsPerQuarter+i]=-x[i];
        x[4*pointsPerQuarter-1-i]=x[i];
        y[4*pointsPerQuarter-1-i]=-y[i]; 
    }
    
    glBegin(GL_LINE_LOOP);
    for (i=0;i<circlePoints;i++)
    {
        glVertex2f(x[i],y[i]);
    }
    glEnd();
    
}

void ellipse(){
    glColor3f(0,0);
    GLfloat angleStep=2*PI/(float)ellipsePoints; 
    gluint pointsPerQuarter=ellipsePoints;///4; 
    GLfloat x[ellipsePoints]; 
    GLfloat y[ellipsePoints]; 
    GLfloat rx=15; 
    GLfloat ry=10; 
    glBegin(GL_LINE_LOOP); 
        for(i=0;i<pointsPerQuarter;i++) 
        { 
            x[i]=rx*cos(i*angleStep); 
            y[i]=ry*sin(i*angleStep); 
        } 
        
        for(i=0;i<ellipsePoints;i++) 
        { 
            glVertex2f(x[i],y[i]); 
        } 
    glEnd(); 
}

void reshape(int w,int h)
{


    glViewport(0,w,h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(-32,32,-24,24);
    glMatrixMode(GL_MODELVIEW);
}


void timer(int value)
{
    glutPostRedisplay();
    glutTimerFunc(500,timer,0);
}

void init(void)
{
    glClearColor(1,0);
    glColor3f(0,0);
}

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    gllinewidth(3);
    ellipse();
    glPushmatrix();
    glTranslatef(-7.0,0.0);
    circle();
    glPopMatrix();
    glPushmatrix();
    glTranslatef(15.0,0.0);
    circlearth();
    glPopMatrix();
    glFlush();
    glutSwapBuffers(); // double buffer
}

int main(int argc,char** argv) {
    glutinit(&argc,argv);
    glutinitwindowPosition(50,50);
    glutinitdisplayMode(gluT_SINGLE | gluT_RGB);
    glutinitwindowSize(640,480); 
    glutCreateWindow("Earth-Sun");
    glMatrixMode(GL_PROJECTION); 
    init();
    glutdisplayFunc(display);
    glutReshapeFunc(reshape);
    glutTimerFunc(0000,0);
    glutMainLoop(); 
    return 0; 
}

解决方法

我制作了全局变量：

double xea = 12,yea = 0;
double ang = 0;

这个glutIdleFunc：

   void idle() {
        xea = 20 * sin(ang);
        yea = 10 * cos(ang);
        ang += 0.0001;
        glutPostRedisplay();
    }

然后glutIdleFunc(idle);注册。

并在显示功能中更改了地球的位置：

glTranslatef(xea,yea,0.0);

而<gl/glut.h>想要<GL/glut.h>。嗯，谁是对的？

现在地球平稳地移动，或多或少在椭圆上。

但是：我注意到与带有 glDrawArrays() 和动画的简单“现代”OpenGL 程序相比，它的功耗很高（风扇立即处于活动状态）。

使用键盘回调中的手动角度增量（而不是空闲回调中的自动 60 Hz），这应该不是问题。

c opengl opengl