piecewise_linear_function.h

#pragma once
 
#include <vector>
 
#include "interval.h"
 
namespace cgv {
namespace math {
 
template<typename T>
struct regular_piecewise_linear_function {
    std::vector<T> values;
    interval<T> domain = { T(0), T(1) };
 
    T evaluate(T x) const {
        x = (x - domain.lower_bound) / domain.size();
 
        if(x <= T(0))
            return values.front();
 
        if(x >= T(1))
            return values.back();
 
        T num_segments = static_cast<T>(values.size() - 1);
        int64_t index = static_cast<int64_t>(x * num_segments);
 
        T step = T(1) / num_segments;
        T prev = static_cast<T>(index) * step;
        T curr = static_cast<T>(index + 1) * step;
        T t = (x - prev) / (curr - prev);
        return interpolate_linear(values[index], values[index + 1], t);
    }
};
 
} // namespace math
} // namespace cgv