我在实现母类的虚函数时遇到了一些问题: 基本上,我的代码如下:
class Shape
{
public:
virtual ~Shape();
virtual bool Intersect (const Ray& ray, double& t) const =0;// to premit abstraktion (definition in sub-classes)
virtual Vector GetNormal(const Vector& at) const =0;
protected:
Color color;
double dc; //diffusive component
};
class Ball: public Shape
{
public:
Ball(const Color& col,const double diff,const double x,const double y,const double z,const double radius):
cx(x),cy(y),cz(z),r(radius)
{
Shape::color=col;
Shape::dc=diff;
assert(radius!=0);
}
virtual bool Intersect (const Ray& ray, double& t)
{
Vector c(cx,cy,cz), s(ray.xs,ray.ys,ray.zs);
Vector v(s-c);
double delta(std::pow(v*ray.dir,2)-v*v+r*r);
if(delta<0) return false;
const double thigh(-v*ray.dir+std::sqrt(delta)), tlow(-v*ray.dir-std::sqrt(delta));
if(thigh<0) return false;
else if (tlow<0){t=thigh; return true;}
else{t=tlow; return true;}
assert(false);//we should never get to this point
};
virtual Vector GetNormal(const Vector& at)
{
Vector normal(at - Vector(cx,cy,cz));
assert(Norm(normal)==r);// the point where we want to get the normal is o the Ball
return normal;
};
private:
// already have color and dc
double cx,cy,cz; //center coordinates
double r;//radius
};
在主函数中,使用以下语句创建一个Ball对象:ball=new Ball(parameters);
出现了错误提示:"cannot allocate an object of type ball because implemented funktionsare pure within ball"。
由于Ball类中的一些函数是纯虚函数,在子类中需要进行实现,因此我不理解为什么无法创建对象。
new
,Jack? - Shoe