Hiya
I'm making a 2d game in SDL and I've come to the collision detection. I plan to give every object on the screen (everything is derived from "Object" with variables for the sprite and co-ordinates) a pointer to a "Shape" and then when I want to test for collisions I just test the two shapes. My problem is when I try to make a Shape, here is my Shape class:
class Rect;
class Circle;
class Shape{
protected:
int m_centerX;
int m_centerY;
public:
int &CenX(){return m_centerX;}
int &CenY(){return m_centerY;}
void Set(int x, int y){CenX() = x; CenY() = y;}
virtual void SetTL(int x, int y){CenX() = x; CenY() = y;}
virtual bool CheckOverlap(Shape *other);
virtual bool CheckOverlap(Rect *other);
virtual bool CheckOverlap(Circle *other);
};
class Rect : public Shape{
protected:
int m_extendX;
int m_extendY;
public:
int &ExtendX(){return m_extendX;}
int &ExtendY(){return m_extendY;}
int MinX(){return CenX() - ExtendX();}
int MaxX(){return CenX() + ExtendX();}
int MinY(){return CenY() - ExtendY();}
int MaxY(){return CenY() + ExtendY();}
int GetWidth(){return 2*ExtendX();}
int GetHeight(){return 2*ExtendY();}
void SetWidth(int width){ExtendX() = width/2;}
void SetHeight(int height){ExtendY() = height/2;}
void SetTL(int x, int y){
CenX() = x + ExtendX();
CenY() = y + ExtendY();
}
bool CheckOverlap(Shape *other);
bool CheckOverlap(Rect *other);
bool CheckOverlap(Circle *other);
Rect(int x, int y, int width, int height){
CenX() = x + width/2;
CenY() = y + width/2;
SetWidth(width);
SetHeight(height);
}
};
class Circle : public Shape{
protected:
int m_radius;
public:
int &Radius(){return m_radius;}
void SetTL(int x, int y){
CenX() = x + Radius();
CenY() = y + Radius();
}
bool CheckOverlap(Shape *other);
bool CheckOverlap(Rect *other);
bool CheckOverlap(Circle *other);
Circle(int x, int y, int radius){
Set(x, y);
Radius() = radius;
}
};
And if you needed it my problem code is:
Shape* myShape = new Circle(50, 50, 20);
And my error message:
Switching to target: default
Compiling: main.cpp
Linking console executable: SDLapp.exe
.objs\main.o:main.cpp:(.text$_ZN5ShapeC2Ev[Shape::Shape()]+0x8): undefined reference to `vtable for Shape'
collect2: ld returned 1 exit status
Any help would be much appreciated.
Whether you think you can or think you can’t, you’re probably right – Henry Ford
