Gradient.h

//
//  Gradient.h
//  Termin8or
//
//  Created by Rasmus Anthin on 2024-09-02.
//

#pragma once
#include <Core/Math.h>
#include <assert.h>


// Param values define the centers of the ranges for the values.
//      t0            t1           t2     t3       : param at center of value range.
//  0    :             :            :      :    1
//  |---------|------------------|-----|--------|
//  |<------->|<---------------->|<--->|<------>|
//      v0             v1           v2      v3     : value ranges.
//
// For equidistant params: t = (1/N:1/N:1)-1/(2*N)
//   where N is the number of gradient nodes.

template<typename T>
struct Gradient
{
  std::vector<std::pair<float, T>> gradient;
  T default_value;
  
  Gradient(T def = T{}) : default_value(def) {}
  Gradient(const std::vector<std::pair<float, T>>& a_gradient, T def = T{})
    : gradient(a_gradient), default_value(def)
  {}
  Gradient(const std::vector<T>& uniform_gradient, T def = T{})
  {
    auto dt = 1.f / uniform_gradient.size();
    auto t = dt - dt/2;
    for (const auto& obj : uniform_gradient)
    {
      gradient.emplace_back(t, obj);
      t += dt;
    }
  }
  
  T operator() (float t) const
  {
    assert(0.f <= t && t <= 1.f);
    float t_dist_min = 2.f;
    T closest_obj = default_value; //Color::Default;
    for (const auto& obj_pair : gradient)
    {
      auto t_dist = std::abs(t - obj_pair.first);
      if (math::minimize(t_dist_min, t_dist))
        closest_obj = obj_pair.second;
    }
    return closest_obj;
  }
};