Center is an attribute of ImplicitSurface.

This way the search space for Marching Cubes is way smaller.

Implicit.hpp

@@ -6,4 +6,8 @@ class ImplicitSurface {
     public:
         virtual double operator() (double x, double y, double z) const = 0;
         double operator()(const Point& pt) const;
+        Point getCenter() { return center;}
+    protected:
+        Point center;
+        ImplicitSurface(Point _center) : center(_center) {}
 };

spheroid.cpp

@@ -5,7 +5,7 @@
 #include "spheroid.hpp"
 
 Spheroid::Spheroid(Point& _center, size_t _p, size_t _q) :
-    center(_center), p(_p), q(_q), stiffness(0) {
+    ImplicitSurface(_center), p(_p), q(_q), stiffness(0) {
         _compute_volume();
     }
 

spheroid.hpp

@@ -31,7 +31,6 @@ class Spheroid : public ImplicitSurface {
          * V is the volume. Extremely useful to have a constant volume in the
          * ball
         **/
-        Point& center;
         double p, q;
         size_t stiffness;
         double V;

tests/TestImplicitSphere.hpp

@@ -5,10 +5,9 @@
 class TestImplicitSphere: public ImplicitSurface {
     public:
         TestImplicitSphere(const Point& center, double r):
-            center(center), radius(r) {}
+            ImplicitSurface(center), radius(r) {}
         virtual double operator()(double x, double y, double z) const;
 
     private:
-        Point center;
         double radius;
 };