src/util/aabb.h


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#pragma once

#include "vector.h"

struct AABB {
  VEC3 min;
  VEC3 max;
};

inline VEC3 aabb_center( const AABB& aabb ) { return (aabb.min + aabb.max) * 0.5f; }
inline VEC3 aabb_half( const AABB& aabb ) { return (aabb.max - aabb.min) * 0.5f; }
inline F32 aabb_support_radius( const AABB& aabb, const VEC3& dir ) {
  VEC3 half = aabb_half( aabb );
  return fabsf(dir.x) * half.x + fabsf(dir.y) * half.y + fabsf(dir.z) * half.z;
}

// returns positive radius in X and negative in Y
inline VEC2 aabb_extend_at_feet( const AABB& aabb, const VEC3& dir ) {
  VEC3 half = aabb_half( aabb );

  F32 hx = half.x;
  F32 hy = half.y;
  F32 hz = half.z * 2;

  F32 lateral = fabsf( dir.x ) * hx + fabsf( dir.y ) * hy;

  F32 pos_z = dir.z > 0 ? dir.z * hz : 0.f;
  F32 neg_z = dir.z < 0 ? (-dir.z) * hz : 0.f;

  return { lateral + pos_z, lateral + neg_z };
}