shapes.hpp

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#pragma once
 
#include <SDL3/SDL.h>
 
#include <cmath>
#include <numbers>
#include <stdexcept>
#include <vector>
 
#include "../math.hpp"
 
namespace sKit {
namespace geom {
 
template <typename T, typename U>
struct Geometry {
  std::vector<T> vertices;
  std::vector<U> indices;
};
 
template <typename T, typename U>
auto circle(float x, float y, float radius, unsigned int resolution = 72)
    -> Geometry<T, U> {
  throw std::runtime_error("");
};
 
template <>
auto circle<SDL_Vertex, int>(
    float x,
    float y,
    float radius,
    unsigned int resolution
) -> Geometry<SDL_Vertex, int>;
 
auto arc(
    float x,
    float y,
    float radius,
    float theta,
    float width,
    float height,
    unsigned int resolution = 100,
    SDL_FColor col = {}
) -> Geometry<SDL_Vertex, int>;
 
namespace vertex {
 
template <typename T>
auto arc(
    float x,
    float y,
    float radius,
    float theta,
    float width,
    float height,
    unsigned int resolution = 100
) -> std::vector<T> {
  static constexpr auto tau = (std::numbers::pi_v<float> * 2.f);
  const float resf = static_cast<float>(resolution);
  const unsigned int arcRes = round((width / tau) * resf);
  std::vector<T> vertices(arcRes * 2 + 3);
  for (unsigned int i = 0; i <= arcRes; i++) {
    {
      const float a = sKit::math::map(i, 0, arcRes, theta, theta + width);
      const float px = cos(a) * (radius - height) + x;
      const float py = sin(a) * (radius - height) + y;
      vertices[i] = T {px, py};
    }
    {
      const float a = sKit::math::map(i, 0, arcRes, theta + width, theta);
      const float px = cos(a) * radius + x;
      const float py = sin(a) * radius + y;
      vertices[arcRes + i + 1] = T {px, py};
    }
  }
  vertices[vertices.size() - 1] = vertices[0];
  return vertices;
};
 
}  // namespace vertex
 
}  // namespace geom
}  // namespace sKit