c++ - 绘制带有飞行路径的地球

Question

我有一个....独特的问题。我正在制作一个游戏，我将在其中动态绘制点(代表城市)以及它们之间的飞行路径。然后用户将选择这些城市并执行进一步的操作。

此外，地球仪必须能够绕一个轴旋转，这样用户才能轻松看到所有城市。

我找到了一种在球体上绘制点和路径的方法。这些点是微小的球体，路径是我生成的贝塞尔曲线。我已将它们包含在 glpushmatrix() 和 glpopmatrix() 中，并在开始时调用 glrotate() 以便所有事物(地球、路径和顶点)一致旋转

我面临的唯一问题是弄清楚用户点击了哪个顶点。 glrotate 修改模型矩阵，所以我是否必须在每次旋转时计算顶点的新位置？我正在使用 glunproject 找出用户点击的位置。或者，还有其他方法可以解决这个问题吗？

这是我的代码:-

float venusRotate;
vector<vector3f>cityVertices;

//bezier curve
GLfloat bezierCurve(float t, GLfloat P0,
                    GLfloat P1, GLfloat P2) {
    // Cubic bezier Curve
    GLfloat point = pow(t,2)*P0 + 2*P1*t*(1-t) + P2*pow(1-t, 2);
    return point;
}


vector3f randomSpherePoint()
{
    float u = static_cast <float> (rand()) / static_cast <float> (RAND_MAX);
    float v = static_cast <float> (rand()) / static_cast <float> (RAND_MAX);
    float theta = 2 * M_PI * u;
    float phi = acos(2*v-1);
    float x=(10*sin(phi)*cos(theta));
    float y=(10 * sin(phi) * sin(theta));
    float z=10*cos(phi);
    return vector3f(x, y, z);
}


void drawRandomSpherePoints()
{
    for (int i=0; i<400; i++)
    {
        glPushMatrix();

        vector3f point=cityVertices.at(i);
        glTranslatef(point.x, point.y, point.z);
        glutSolidSphere(0.25, 10, 10);
        glPopMatrix();
    }

}
vector3f GetOGLPos(int x, int y)
{
    GLint viewport[4];
    GLdouble modelview[16];
    GLdouble projection[16];
    GLfloat winX, winY, winZ;
    GLdouble posX, posY, posZ;

    glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
    glGetDoublev( GL_PROJECTION_MATRIX, projection );
    glGetIntegerv( GL_VIEWPORT, viewport );

    winX = (float)x;
    winY = (float)viewport[3] - (float)y;
    glReadPixels( x, int(winY), 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ );

    gluUnProject( winX, winY, winZ, modelview, projection, viewport, &posX, &posY, &posZ);
    return vector3f(posX, posY, posZ);
}

void mouseClick(int button,int state,int x, int y)
{
    vector3f Coord=GetOGLPos(x, y);
    cout<<Coord.x<<" "<<Coord.y<<" "<<Coord.z<<endl;
//    for (int i=0;i<cityVertices.size();i++)
//    {
//        if (Coord.x-cityVertices.at(i).x<CLICK_ACCURACY && Coord.z-cityVertices.at(i).z<CLICK_ACCURACY && Coord.z-cityVertices.at(i).z<CLICK_ACCURACY  ) {
//        }
//    }
}



void preProcessEvents()
{
    CURRENT_TIME=(float)glutGet(GLUT_ELAPSED_TIME);
    DELTA_TIME=CURRENT_TIME-LAST_TIME;
    LAST_TIME=CURRENT_TIME;


    mouse::update();
    //mouse processing
    Camera::rotationAngles.y+=(float)mouse::deltaX*MOUSE_SENSITIVITY;
    Camera::rotationAngles.x-=(float)mouse::deltaY*MOUSE_SENSITIVITY;

    if (Camera::rotationAngles.x>MAX_TILT)
    {
        Camera::rotationAngles.x=MAX_TILT;
    }
    else if (Camera::rotationAngles.x<-1*MAX_TILT)
    {
        Camera::rotationAngles.x=-1*MAX_TILT;
    }
    if (keyBoard::key['w'])
    {
        Camera::position.z-=WALKING_SPEED*DELTA_TIME*Math::sind(Camera::rotationAngles.y);
        Camera::position.x-=WALKING_SPEED*DELTA_TIME*Math::cosd(Camera::rotationAngles.y);
    }
    else if (keyBoard::key['s'])
    {
        Camera::position.z+=WALKING_SPEED*DELTA_TIME*Math::sind(Camera::rotationAngles.y);
        Camera::position.x+=WALKING_SPEED*DELTA_TIME*Math::cosd(Camera::rotationAngles.y);
    }
    else if (keyBoard::key['a'])
    {
        Camera::rotationAngles.y-=WALKING_SPEED*DELTA_TIME*3;
    }
    else if (keyBoard::key['d'])
    {
        Camera::rotationAngles.y+=WALKING_SPEED*DELTA_TIME*3;
    }
    else if (keyBoard::key['f'])
    {
        venusRotate++;
    }
    else if (keyBoard::key[' '])
    {
        glutDestroyWindow(subWindow);
    }

}
void reshape(int w, int h)
{
    float aspectRatio;
    if (h==0)
    {
        h=1;
    }
    aspectRatio=float(w)/float(h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glViewport(0, 0, w ,h);
    gluPerspective(45, aspectRatio, 0.01, 100000000);
    glMatrixMode(GL_MODELVIEW);
}


void display()
{
    preProcessEvents();
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    gluLookAt(Camera::position.x, Camera::position.y, Camera::position.z,
              Camera::position.x+Math::sind(Camera::rotationAngles.x)*Math::cosd(Camera::rotationAngles.y),
              Camera::position.y+Math::cosd(Camera::rotationAngles.x),
              Camera::position.z+Math::sind(Camera::rotationAngles.x)*Math::sind(Camera::rotationAngles.y),
              0.0, 1.0, 0.0);
    glBegin(GL_TRIANGLES);
    glColor3f(1, 0, 0);
    glVertex3f(-1, 0,-3);
    glColor3f(0, 1, 0);
    glVertex3f(0.0f, 2.0f,-3);
    glColor3f(0, 0, 1);
    glVertex3f(1.0f, 0.0f,-3);
    glEnd();





    glBindTexture(GL_TEXTURE_2D, tex->textureID);

    glBegin(GL_QUADS);

    glColor3f(1, 1, 1);
    glTexCoord2f(100, 100);
    glVertex3f(100,0,100);

    glTexCoord2f(-100, 100);
    glVertex3f(-100,0,100);

    glTexCoord2f(-100,-100);
    glVertex3f(-100,0,-100);

    glTexCoord2f(100,-100);
    glVertex3f(100,0,-100);

    glEnd();
    glBindTexture(GL_TEXTURE_2D, 0);


    glPushMatrix();
    object1.draw();
    glPopMatrix();

    //globe
    glTranslatef(-10.0, 10.0, 0.0);
    glBindTexture(GL_TEXTURE_2D, tex2->textureID);
    gluQuadricTexture(quad,1);
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glRotatef(-90, 1.0f, 0.0f, 0.0f);
    glRotatef(venusRotate, 0.0, 0.0, 1.0);
    drawRandomSpherePoints();

    for (int i=0; i<cityVertices.size()-1; i++)
    {
        vector3f start=cityVertices.at(i);
        vector3f end=cityVertices.at(i+1);
        vector3f perpBisectorDirection=vector3f((start.x+end.x)/2,(start.y+end.y)/2,(start.z+end.z)/2);
        vector3f tan1(perpBisectorDirection.x/10*15,perpBisectorDirection.y/10*15,perpBisectorDirection.z/10*15);
        glColor3f(1.0, 0.0, 0.0);
        glLineWidth(12.0);
        glBegin(GL_LINE_STRIP);

        int t = 30;
        for (int i = 0; i <= t; i++) {
            float pos = (float) i / (float) t;
            GLfloat x = bezierCurve( pos,start.x, tan1.x, end.x);
            GLfloat y = bezierCurve( pos,start.y, tan1.y, end.y);
            // In our case, the z should always be empty
            GLfloat z = bezierCurve(pos,start.z, tan1.z, end.z);

            vector3f result(x, y, z);
            glVertex3f(x, y, z);
        }
        glEnd();

    }
    gluSphere(quad,10,20,20);
    glPopMatrix();
    glBindTexture(GL_TEXTURE_2D, 0);

    glutSwapBuffers();
}

Answer 1

Opengl 有一个选择模式

glRenderMode(GL_SELECT);