Surfaces now provide a location hint

This is supposed to be a point in space close to the surface

Implicit.hpp

@@ -8,6 +8,8 @@ class ImplicitSurface {
         double operator()(const Point& pt) const;
         Point getCenter() const { return center;}
 
+        virtual Point location_hint() const = 0;
+
         /// Compute the normal vector to the isosurface at `pt`
         Point normal_at(const Point& pt) const;
     protected:

PerlinNoise.cpp

@@ -121,3 +121,11 @@ Point PerlinNoise::normal_vector(double x, double y) {
     );
     return product;
 }
+
+Point PerlinNoise::location_hint() const {
+    return location_hint(0, 0);
+}
+
+Point PerlinNoise::location_hint(double x, double z) const {
+    return Point(x, noise(x, z), z);
+}

PerlinNoise.hpp

@@ -15,6 +15,9 @@ class PerlinNoise : public ImplicitSurface {
         double operator() (double _x, double _y, double _z) const;
         double noise(double x, double y) const;
         Point normal_vector(double x, double y);
+
+        virtual Point location_hint() const;
+        Point location_hint(double x, double z) const;
     private:
         double noise(double x, double y, double z) const;
         double fade(double t) const;

spheroid.cpp

@@ -75,3 +75,7 @@ double Spheroid::operator() (double _x, double _y, double _z) const {
                   + pow(_y, 2) / pow(p, 2)
                   + pow(_z, 2) / pow(q, 2) -1);
 }
+
+Point Spheroid::location_hint() const {
+    return Point(0, p, 0);
+}

spheroid.hpp

@@ -23,6 +23,8 @@ class Spheroid : public ImplicitSurface {
         void check_perlin_collision(PerlinNoise perlin);
         Point getNormalVector() const { return normal_vector;}
         double operator() (double _x, double _y, double _z) const;
+
+        virtual Point location_hint() const;
     private:
         /**
          * p corresponds to the half-height of the ball,

tests/TestImplicitSphere.cpp

@@ -7,3 +7,7 @@ double TestImplicitSphere::operator()(double x, double y, double z) const {
             + sq(center.z - z))
         + sq(radius);
 }
+
+Point TestImplicitSphere::location_hint() const {
+    return Point(center.x + radius, center.y, center.z);
+}

tests/TestImplicitSphere.hpp

@@ -8,6 +8,8 @@ class TestImplicitSphere: public ImplicitSurface {
             ImplicitSurface(center), radius(r) {}
         virtual double operator()(double x, double y, double z) const;
 
+        virtual Point location_hint() const;
+
     private:
         double radius;
 };