Added interpolating deformer

src/interpolating_deformer.cpp

+#include <interpolating_deformer.hpp>
+#include <vec3.hpp>
+#include <cmath>
+#include <fstream>
+#include <algorithm>
+
+interpolating_deformer::interpolating_deformer(std::string filename, double maxelong, double z_zero, double up, point3 center, double radius)
+: maxelong(maxelong), z_zero(z_zero), up(up), center(center), radius(radius){
+  //Load interpolation table
+  std::fstream file(filename);
+  size_t num_points;
+  file >> num_points;
+  rs = std::vector<double>(num_points);
+  zs = std::vector<double>(num_points);
+  for(size_t i = 0; i < num_points; ++i){
+    file >> rs[i] >> zs[i];
+  }
+  //Rescale interpolation table
+  for(size_t i = 0; i < num_points; ++i){
+    rs[i] *= radius;
+    zs[i] = z_zero + up * maxelong * zs[i];
+  }
+}
+
+double interpolating_deformer::z(double x, double y) const{
+  double r = std::sqrt((center.x()-x)*(center.x()-x) + (center.y()-y)*(center.y()-y));
+
+  auto it_upper = std::find_if(rs.begin(), rs.end(), [r](double r_int){ return r_int >= r; });
+  if(it_upper == rs.begin()){
+    return zs.front();
+  }
+  else if(it_upper == rs.end()){
+    return zs.back();
+  }
+  else{
+    double upper_dist = (*it_upper) - r;
+    double lower_dist = r - (*(it_upper-1));
+    size_t i_upper = it_upper - rs.begin();
+    size_t i_lower = i_upper - 1;
+    return (lower_dist * zs[i_upper] + upper_dist * zs[i_lower]) / (upper_dist + lower_dist);
+  }
+}