TBinaryBvhNode.h

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#pragma once
 
#include "Math/Geometry/TAABB3D.h"
 
#include <Common/primitive_type.h>
#include <Common/utility.h>
 
#include <cstddef>
#include <type_traits>
 
namespace ph::math
{
 
template<typename Item, typename Index>
class TBinaryBvhNode final
{
    static_assert(std::is_unsigned_v<Index>);
 
    inline static constexpr std::size_t NUM_FLAG_BITS  = 2;
    inline static constexpr std::size_t NUM_ITEMS_BITS = sizeof_in_bits<uint8>() - NUM_FLAG_BITS;
 
    inline static constexpr uint8 FLAG_BITS_MASK = 0b11;
    inline static constexpr uint8 X_AXIS_FLAG    = 0b00;
    inline static constexpr uint8 Y_AXIS_FLAG    = 0b01;
    inline static constexpr uint8 Z_AXIS_FLAG    = 0b10;
    inline static constexpr uint8 LEAF_FLAG      = 0b11;
 
public:
    inline static constexpr std::size_t MAX_NODE_ITEMS = (std::size_t(1) << NUM_ITEMS_BITS) - 1;
 
    static auto makeInternal(
        const AABB3D& nodeAABB,
        std::size_t childOffset,
        std::size_t splitAxis)
    -> TBinaryBvhNode;
 
    static auto makeLeaf(
        const AABB3D& nodeAABB,
        std::size_t itemOffset,
        std::size_t numItems)
    -> TBinaryBvhNode;
 
    TBinaryBvhNode();
 
    const AABB3D& getAABB() const;
    bool isLeaf() const;
    bool isInternal() const;
    std::size_t getChildOffset() const;
    std::size_t getSplitAxis() const;
    std::size_t getItemOffset() const;
    std::size_t numItems() const;
 
private:
    AABB3D m_aabb;
 
    union
    {
        Index u0_childOffset;// for internal
        Index u0_itemOffset; // for leaf
    };
 
    uint8 m_numItemsAndFlags;
};
 
}// end namespace ph::math
 
#include "Math/Algorithm/BVH/TBinaryBvhNode.ipp"