どのような形状の交差関数を書くか

Question

交差を検出して真または偽を返す関数を書く必要があります。

私はShape.cppファイルとrectangle.cppを持っていますが、circle.cppファイルはそれを継承しています。私はそれを計算しようとしましたが、失敗しました。エラーはありませんが、プログラムが起動するとクラッシュします。私の質問はなぜそれがクラッシュするのですか？私の方法は間違っていますか？ここにはcircle.cppファイルがあります。

bool Circ::intersects(Shape* pshape) 
{ 
    Rect *p1 = dynamic_cast<Rect*>(pshape); 
    Circ *p2 = dynamic_cast<Circ*>(pshape); 

    if(p1) 
    { 
     float circleDistance_x = abs(p2->getPos().x - p1->getPos().x); 
     float circleDistance_y = abs(p2->getPos().y - p1->getPos().y); 

     if(circleDistance_x > (p1->getSize().x/2 + p2->getRad())) 
      return false; 
     if(circleDistance_y > (p1->getSize().y/2 + p2->getRad())) 
      return false; 
     if(circleDistance_x <= (p1->getSize().x/2)) 
      return true; 
     if(circleDistance_y <= (p1->getSize().y/2)) 
      return true; 
     float cornerDistance_sq = (circleDistance_x - (p1->getSize().x/2)) + (circleDistance_y - (p1->getSize().y/2))*(circleDistance_y - (p1->getSize().y/2)); 

     return (cornerDistance_sq <= p2->getRad()^2); 

    } 

    return false; 
} 

これは、すべて私が書いたいコードではありません。しかし、それが失敗すると、私は書くのをやめました。

と私のSHAPES.Hファイル

#ifndef _SHAPES_H 
#define _SHAPES_H 


struct Point2d 
{ 
    float x, y; 

}; 
struct Point3d 
{ 
    float r, g, b; 

}; 

class Shape 
{ 
protected: 
    bool m_bMarked; 
    Point3d m_col; 
    Point2d m_veldir; 
    Point2d m_pos; 
    float m_vel; 
public: 
    Shape(Point2d& pos, Point2d& veldir, float vel, Point3d& col) 
     :m_pos(pos),m_veldir(veldir),m_vel(vel),m_col(col) 
    { 
     m_bMarked = false; 
    } 
    virtual ~Shape() {} 
    virtual void draw() = 0; 
    virtual bool intersects(Shape*) = 0; 
    inline void move() { m_pos.x += m_veldir.x*m_vel; m_pos.y += m_veldir.y*m_vel; } 
    inline void invert_xdir() { m_veldir.x *= -1; } 
    inline void invert_ydir() { m_veldir.y *= -1; } 
    inline void MarkShape() { m_bMarked = true; } 
    inline void UnMarkShape() { m_bMarked = false; } 
    inline bool isMarked() { return m_bMarked; } 
    inline void increase_vel() { m_vel += 0.01f; } 
    inline void decrease_vel() { m_vel -= 0.01f; } 

}; 


#endif 

そして最後に、私のShapesMain.cppファイル

#include <time.h> 
#include <GL/glut.h> 
#include <cmath> 

#include "Rectangle.h" 
#include "Circle.h" 


// YOU CAN CHANGE THE NUMBER OF SHAPES 
#define SHAPE_COUNT 20 

// YOU CAN MODIFY WINDOW SIZE BY CHANGING THESE 
// YOU MAY ALSO VIEW WINDOW IN FULL SCREEN 
#define WINDOWX 500 
#define WINDOWY 500 

// UNCOMMENT THE LINE BELOW TO STOP MOVING SHAPES 
//#define NO_MOTION 

// CHANGE THESE DIMENSIONS HOWEVER YOU LIKE 
#define MAX_SHAPE_DIM 70 
#define MIN_SHAPE_DIM 10 

float g_windowWidth = WINDOWX; 
float g_windowHeight = WINDOWY; 

Shape* g_shapeList[SHAPE_COUNT]; 
int  g_numShapes = 0; 
bool g_bShowIntersection = true; 



//------------------------------------ 

void Initialize() 
{ 
    srand (time(NULL)); 

    // delete previous shapes, if there is any 
    if (g_numShapes > 0) 
    { 
     for (int i = 0; i < g_numShapes; i++) 
      delete g_shapeList[i]; 
    } 

    // create a new shape repository 
    do { 
     g_numShapes = rand() % SHAPE_COUNT; // number of shapes are randomly determined  
    } while (g_numShapes < 5); // we dont want to have less than 5 shapes 


    int rect_count = g_numShapes * (rand() % 10/10.0f); 
    int circle_count = g_numShapes - rect_count; 

    int half_wind_x = 3* g_windowWidth/4; 
    int half_wind_y = 3* g_windowHeight/4; 
    int max_dim = MAX_SHAPE_DIM; // max dim. of any shape 
    int min_dim = MIN_SHAPE_DIM; // min dim. of any shape 
    int quad_wind = g_windowWidth/4; 

    for (int i= 0; i<g_numShapes; i++) 
    { 

     float x, y; 
     float v1, v2; 

     // set positions 
     do { 
      x = rand() % half_wind_x; 
     } while (x <= quad_wind); 

     do { 
      y = rand() % half_wind_y; 
     } while (y <= quad_wind); 
     Point2d pos = { x,y }; 

     // set velocity directions 
     do{ 
      v1 = rand() % 10/10.0f; 
      v2 = rand() % 10/10.0f;   
     } while (v1 == 0 || v2 == 0); 

     v1 *= (rand() % 2) ? -1 : 1; 
     v2 *= (rand() % 2) ? -1 : 1; 
     float vnorm = sqrt(v1*v1 + v2*v2); 
     Point2d veldir = { v1/vnorm, v2/vnorm }; 

     // set velocity 
     float vel; 
     do { 
      vel = rand() % 2/10.0f; 
     } while (vel == 0); 

#ifdef NO_MOTION 
     vel = 0.0f; 
#endif 
     //set color 
     float R = rand()%100/100.0f; 
     float G = rand()%100/100.0f; 
     float B = rand()%100/100.0f; 
     Point3d color = { R,G,B }; 

     // construct objects 
     if (i < rect_count) 
     { 
      float wx; 
      float wy; 
      do { 
       wx = rand() % quad_wind; 
      } while (wx < min_dim || wx>max_dim); 

      do { 
       wy = rand() % quad_wind; 
      } while (wy < min_dim || wy>max_dim); 

      Point2d size = { wx, wy };   

      Rect* pRect = new Rect(pos, size, veldir, vel, color); 
      g_shapeList[i] = pRect; 
     } 
     else 
     { 
      float rad; 
      do { 
       rad = rand() % quad_wind; 
      } while (rad < min_dim || rad>max_dim); 


      Circ* pCirc = new Circ(pos, rad, veldir, vel, color); 
      g_shapeList[i] = pCirc; 
     } 
    } 

    glClearColor(1.0f, 1.0f, 1.0f, 1.0f); 

} 
//------------------------------------- 
// This function handles the intersections of shapes. 
// if the user is not interested in marking intersections 
// s/he can set bMarkIntersections to false..in this case 
// no intersection test is performed 
void MarkObjects(bool bMarkIntersections) 
{ 
    if (bMarkIntersections == false) 
    { 
     for (int i = 0; i < g_numShapes; i++) 
      g_shapeList[i]->UnMarkShape(); 
    } 
    else 
    { 
     // reset the states of all shapes as unmarked 
     for (int i = 0; i < g_numShapes; i++) 
      g_shapeList[i]->UnMarkShape(); 

     for (int i = 0; i < g_numShapes; i++) 
     {   
      for (int j = i+1; j < g_numShapes; j++) 
      { 

       if (g_shapeList[i]->intersects(g_shapeList[j])) 
       { 
        g_shapeList[i]->MarkShape(); 
        g_shapeList[j]->MarkShape(); 

       } 
      } 
     } 
    } 

} 
//------------------------------------ 
void UpdateData() 
{ 
    // create viewport bounding rectangles to keep the shapes within the viewport 
    Point2d Winpos = { -1.0,0.0 }; 
    Point2d Winsize = { 1.0 , g_windowHeight }; 
    Point2d Winveldir = { 0,0 }; // dummy veldir 
    float Winvel = 0.0f; //not moving 
    Point3d Wincol = { 0,0,0 }; // dummy color 
    Rect WindowRectLeft(Winpos, Winsize, Winveldir, Winvel, Wincol); 
    Winpos.x = 0.0; Winpos.y = -1.0; 
    Winsize.x = g_windowWidth; Winsize.y = 1.0; 
    Rect WindowRectBottom(Winpos, Winsize, Winveldir, Winvel, Wincol); 
    Winpos.x = g_windowWidth; Winpos.y = 0.0; 
    Winsize.x = 1; Winsize.y = g_windowHeight; 
    Rect WindowRectRight(Winpos, Winsize, Winveldir, Winvel, Wincol); 
    Winpos.x = 0.0; Winpos.y = g_windowHeight; 
    Winsize.x = g_windowWidth; Winsize.y = 1.0f; 
    Rect WindowRectUp(Winpos, Winsize, Winveldir, Winvel, Wincol); 

    for (int i = 0; i < g_numShapes; i++) 
    { 
     // move the shape 
     g_shapeList[i]->move(); 

     // if it bounces to the window walls, invert its veldir 
     if (g_shapeList[i]->intersects(&WindowRectLeft) || 
      g_shapeList[i]->intersects(&WindowRectRight)) 
      g_shapeList[i]->invert_xdir(); 

     if (g_shapeList[i]->intersects(&WindowRectBottom) || 
      g_shapeList[i]->intersects(&WindowRectUp)) 
      g_shapeList[i]->invert_ydir(); 
    } 
} 
//------------------------------------ 
void ChangeSize(GLsizei w, GLsizei h) 
{ 
    if(h == 0) 
     h = 1; 

    glViewport(0, 0, w, h); 

    glMatrixMode(GL_PROJECTION); 
    glLoadIdentity(); 

    g_windowHeight = h; 
    g_windowWidth = w; 

    glOrtho(0, g_windowWidth, 0, g_windowHeight , 1.0f, -1.0f); 

    glMatrixMode(GL_MODELVIEW); 
    glLoadIdentity(); 
} 
//------------------------------------ 
void processNormalKeys(unsigned char key, int x, int y) 
{ 

    if (key == 'q') // PRESS 'q' to terminate the application 
     exit(0); 
    if(key=='r') // PRESS 'r' ket to reset the shapes 
     Initialize(); 
    if (key == 's') // toggle between showing the intersections or not 
     g_bShowIntersection = g_bShowIntersection ? false: true; 


} 
//------------------------------------ 
void processSpecialKeys(int key, int x, int y) 
{ 

    switch(key) { 
     case GLUT_KEY_LEFT :     
      break; 
     case GLUT_KEY_RIGHT :  
      break; 
     case GLUT_KEY_UP: 
      // PRESSING UP ARROW KEY INCREASES THE SHAPE VELOCITIES 
      for (int i = 0; i < g_numShapes; i++) 
       g_shapeList[i]->increase_vel(); 
      break; 
     case GLUT_KEY_DOWN: 
      // PRESSING DOWN ARROW KEY DECREASES THE SHAPE VELOCITIES 
      for (int i = 0; i < g_numShapes; i++) 
       g_shapeList[i]->decrease_vel(); 

      break; 
    } 

} 

//------------------------------------- 
void display() { 


    glClear(GL_COLOR_BUFFER_BIT); // Clear the color buffer 

    glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); 

    UpdateData(); 
    MarkObjects(g_bShowIntersection); 

    glMatrixMode(GL_MODELVIEW); 
    glLoadIdentity(); 

    for (int i= 0; i<g_numShapes; i++) 
     g_shapeList[i]->draw(); 


    glutSwapBuffers(); 
} 
//------------------------------------ 
int main(int argc, char* argv[]) 
{ 

    glutInit(&argc, argv);   // Initialize GLUT 
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB); 
    glutInitWindowPosition(100,100); 
    glutInitWindowSize(WINDOWX, WINDOWY); 



    glutCreateWindow("COM102B - PA4"); 


    // Register callback handler for window re-paint 
    glutDisplayFunc(display);  
    glutReshapeFunc(ChangeSize); 
    glutIdleFunc(display); 
    glutKeyboardFunc(processNormalKeys); 
    glutSpecialFunc(processSpecialKeys); 

    Initialize(); 


    glutMainLoop();     // Enter infinitely event-processing loop 

    return 0; 
} 

Answer 1

あなたの問題は、これらの行にある：あなたがのRectを継承していない限り

Rect *p1 = dynamic_cast<Rect*>(pshape); 
Circ *p2 = dynamic_cast<Circ*>(pshape); 

Circから、またはその逆に、これがあなたのプログラムをクラッシュさせる原因になります。あなたがReであれば、あなたのpShapeをCircにキャストすることはできませんct、Rectオブジェクトを関数に渡すと、Rect *に正しくキャストされますが、Circ *がnullptrを返して失敗するので、p2からメソッドにアクセスしようとすると、無効なメモリにアクセスしているのでクラッシュします0x00000000の）：メソッドが円からあるので、

if(p1) 
     { 
      float circleDistance_x = abs(p2->getPos().x - p1->getPos().x); 
      float circleDistance_y = abs(p2->getPos().y - p1->getPos().y); 

      if(circleDistance_x > (p1->getSize().x/2 + p2->getRad())) 
       return false; 
      if(circleDistance_y > (p1->getSize().y/2 + p2->getRad())) 
       return false; 
      if(circleDistance_x <= (p1->getSize().x/2)) 
       return true; 
      if(circleDistance_y <= (p1->getSize().y/2)) 
       return true; 
      float cornerDistance_sq = (circleDistance_x - (p1->getSize().x/2)) + (circleDistance_y - (p1->getSize().y/2))*(circleDistance_y - (p1->getSize().y/2)); 

      return (cornerDistance_sq <= p2->getRad()^2); 

     } 

それで、あなたは単純に最初のP1ポインタをキャストすることができ、P2ポインタのための必要はありませんので、それはそれはのCIRC Objectから呼ばれていたことは明らかです。ライン上でも

Rect *p1 = dynamic_cast<Rect*>(pshape); 
    if(p1) 
     { 
      float circleDistance_x = abs(getPos().x - p1->getPos().x); 
      float circleDistance_y = abs(getPos().y - p1->getPos().y); 

      if(circleDistance_x > (p1->getSize().x/2 + getRad())) 
       return false; 
      if(circleDistance_y > (p1->getSize().y/2 + getRad())) 
       return false; 
      if(circleDistance_x <= (p1->getSize().x/2)) 
       return true; 
      if(circleDistance_y <= (p1->getSize().y/2)) 
       return true; 
      float cornerDistance_sq = (circleDistance_x - (p1->getSize().x/2)) + (circleDistance_y - (p1->getSize().y/2))*(circleDistance_y - (p1->getSize().y/2)); 

      return (cornerDistance_sq <= getRad()^2); 

     } 

：

return (cornerDistance_sq <= getRad()^2) 

は、私はあなたが半径広場を取得しようとしていると思いますが、これは文句を言わないそれを行う、それが実際にやっていることは< becouse

(cornerDistance_sq <= getRad())^2 

です=は^に優先順位があり、^は平方演算子ではありません。ビット演算子です。それでは、あなたが実際に欲しいのです：

return cornerDistance_sq <= getRad() * getRad();