volume_bounds.hpp

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#pragma once
#include "voxel_constants.hpp"
 
#include <algorithm>
#include <cmath>
#include <glm/glm.hpp>
 
namespace voxel {
 
[[nodiscard]]
inline auto localExtent(glm::uvec3 brick_dims) noexcept -> glm::vec3 {
  return glm::vec3(brick_dims) * k_brick_size;
}

[[nodiscard]]
inline auto worldBoundingSphere(const glm::mat4& model, glm::uvec3 brick_dims) -> glm::vec4 {
  const glm::vec3 extent = localExtent(brick_dims);
  const glm::vec3 centre = glm::vec3(model * glm::vec4(extent * 0.5f, 1.0f));
 
  float radius_squared = 0.0f;
  for (int corner = 0; corner < 8; ++corner) {
    const glm::vec3 local(
        (corner & 1) != 0 ? extent.x : 0.0f, (corner & 2) != 0 ? extent.y : 0.0f, (corner & 4) != 0 ? extent.z : 0.0f
    );
    const glm::vec3 offset = glm::vec3(model * glm::vec4(local, 1.0f)) - centre;
    radius_squared = std::max(radius_squared, glm::dot(offset, offset));
  }
  return {centre, std::sqrt(radius_squared)};
}

[[nodiscard]]
inline auto containsPoint(const glm::mat4& inverse_model, glm::uvec3 brick_dims, glm::vec3 world_point, float margin = 0.0f)
    -> bool {
  const glm::vec3 local = glm::vec3(inverse_model * glm::vec4(world_point, 1.0f));
  const float largest_scale = std::max(
      {glm::length(glm::vec3(inverse_model[0])),
       glm::length(glm::vec3(inverse_model[1])),
       glm::length(glm::vec3(inverse_model[2]))}
  );
  const glm::vec3 guard(margin * largest_scale);
  return glm::all(glm::greaterThanEqual(local, -guard)) && glm::all(glm::lessThanEqual(local, localExtent(brick_dims) + guard));
}
 
}