voxel_constants.hpp

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#pragma once
 
#include <cstdint>
 
namespace voxel {
 
inline constexpr float k_voxel_size = 0.1f;
 
inline constexpr uint32_t k_brick_dim = 8;
 
inline constexpr uint32_t k_brick_voxel_count = k_brick_dim * k_brick_dim * k_brick_dim;
 
inline constexpr float k_brick_size = static_cast<float>(k_brick_dim) * k_voxel_size;
 
inline constexpr uint32_t k_region_dim_bricks = 32;
 
inline constexpr uint32_t k_region_dim_voxels = k_region_dim_bricks * k_brick_dim;
 
inline constexpr float k_region_size = static_cast<float>(k_region_dim_bricks) * k_brick_size;
 
inline constexpr uint32_t k_palette_size = 256;
 
inline constexpr uint8_t k_empty_palette_index = 0;
 
enum class BrickTag : uint8_t {
  empty = 0,
  uniform = 1,
  shared = 2,
  owned = 3,
};
 
inline constexpr uint32_t k_brick_tag_bits = 2;
 
inline constexpr uint32_t k_brick_payload_mask = (1u << (32 - k_brick_tag_bits)) - 1u;
 
struct BrickEntry {
  uint32_t value = 0;
 
  [[nodiscard]]
  static constexpr auto make(BrickTag tag, uint32_t payload) noexcept -> BrickEntry {
    return BrickEntry {(payload & k_brick_payload_mask) << k_brick_tag_bits | static_cast<uint32_t>(tag)};
  }
 
  [[nodiscard]]
  constexpr auto tag() const noexcept -> BrickTag {
    return static_cast<BrickTag>(value & ((1u << k_brick_tag_bits) - 1u));
  }

  [[nodiscard]]
  constexpr auto payload() const noexcept -> uint32_t {
    return value >> k_brick_tag_bits;
  }
 
  [[nodiscard]]
  constexpr auto isPooled() const noexcept -> bool {
    const auto t = tag();
    return t == BrickTag::shared || t == BrickTag::owned;
  }
 
  [[nodiscard]]
  constexpr auto operator==(const BrickEntry&) const noexcept -> bool = default;
};
 
static_assert(k_brick_dim * k_brick_dim == 64, "a brick z-slice must be exactly 64 bits");
static_assert(k_brick_voxel_count == 512, "a brick must be 512 voxels");
static_assert(sizeof(BrickEntry) == 4, "an indirection entry must be four bytes");
static_assert(BrickEntry {}.tag() == BrickTag::empty, "a zeroed indirection grid must read as empty");
 
}