338 lines
12 KiB
C#
338 lines
12 KiB
C#
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// <copyright file="BoundingBox.cs">
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// Distributed under the BSD Licence (see LICENCE file).
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//
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// Copyright (c) 2014, Nition, http://www.momentstudio.co.nz/
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// Copyright (c) 2017, Máté Cserép, http://codenet.hu
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// All rights reserved.
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// </copyright>
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namespace Octree
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{
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using System;
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using System.Runtime.Serialization;
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/// <summary>
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/// Represents an axis aligned bounding box (AABB).
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/// </summary>
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/// <remarks>
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/// This class was inspired by the Bounds type of the Unity Engine and
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/// designed with the exact same interface to provide maximum compatibility.
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/// </remarks>
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public struct BoundingBox
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{
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Point _min;
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Point _max;
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Point _center;
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Point _extents;
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/// <summary>
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/// Gets or sets the center of the bounding box.
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/// </summary>
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public Point Center
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{
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get { return _center; }
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set
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{
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_center = value;
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UpdateMinMaxFromCenterOrExtents();
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}
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}
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/// <summary>
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/// Gets or sets the extents of the bounding box. This is always half of the <see cref="Size"/>.
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/// </summary>
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public Point Extents
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{
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get { return _extents; }
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set
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{
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_extents = value;
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UpdateMinMaxFromCenterOrExtents();
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}
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}
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/// <summary>
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/// Gets or sets the size of the bounding box. This is always twice as large as the <see cref="Extents"/>.
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/// </summary>
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public Point Size
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{
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get { return Extents * 2; }
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set { Extents = value * 0.5f; }
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}
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/// <summary>
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/// Gets or sets the minimal point of the box.
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/// </summary>
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/// <remarks>
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/// This is always equal to <c>center-extents</c>.
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/// </remarks>
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public Point Min
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{
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get { return _min; }
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set { SetMinMax(value, _max); }
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}
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/// <summary>
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/// Gets or sets the maximal point of the box.
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/// </summary>
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/// <remarks>
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/// This is always equal to <c>center+extents</c>.
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/// </remarks>
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public Point Max
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{
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get { return _max; }
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set { SetMinMax(_min, value); }
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}
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private void UpdateMinMaxFromCenterOrExtents()
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{
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SetMinMax(Center - Extents, Center + Extents);
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}
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/// <summary>
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/// Creates a new bounding box.
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/// </summary>
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/// <param name="center">The center of the box.</param>
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/// <param name="size">The size of the box.</param>
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public BoundingBox(Point center, Point size)
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{
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_center = center;
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_extents = size * 0.5f;
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_min = _max = new Point();
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UpdateMinMaxFromCenterOrExtents();
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}
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/// <summary>
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/// Sets the bounds to the min and max value of the box.
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/// </summary>
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/// <param name="min">The minimal point.</param>
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/// <param name="max">The maximal point.</param>
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public void SetMinMax(Point min, Point max)
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{
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_min = min;
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_max = max;
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_extents = (_max - _min) * 0.5f;
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_center = _min + _extents;
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}
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/// <summary>
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/// Grows the bounding box include the point.
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/// </summary>
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/// <param name="point">The specified point to include.</param>
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public void Encapsulate(Point point)
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{
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SetMinMax(Point.Min(Min, point), Point.Max(Max, point));
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}
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/// <summary>
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/// Grows the bounding box include the other box.
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/// </summary>
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/// <param name="box">The specified box to include.</param>
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public void Encapsulate(BoundingBox box)
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{
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Encapsulate(box.Center - box.Extents);
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Encapsulate(box.Center + box.Extents);
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}
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/// <summary>
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/// Expands the bounds by increasing its <see cref="Size"/> by <paramref name="amount"/> along each side.
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/// </summary>
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/// <param name="amount">The expansions for each dimension.</param>
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public void Expand(double amount)
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{
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amount *= 0.5f;
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Extents += new Point(amount, amount, amount);
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}
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/// <summary>
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/// Expands the bounds by increasing its <see cref="Size"/> by <paramref name="amount"/> along each side.
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/// </summary>
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/// <param name="amount">The expansions for each dimension in order.</param>
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public void Expand(Point amount)
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{
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Extents += amount * 0.5f;
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}
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/// <summary>
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/// Determines whether the box contains the point.
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/// </summary>
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/// <param name="point">The point to test.</param>
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/// <returns><c>true</c> if the box contains the point; otherwise, <c>false</c>.</returns>
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public bool Contains(Point point)
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{
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return
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Min.X <= point.X && Max.X >= point.X &&
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Min.Y <= point.Y && Max.Y >= point.Y &&
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Min.Z <= point.Z && Max.Z >= point.Z;
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}
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/// <summary>
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/// Determines whether the bounding box intersects with another box.
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/// </summary>
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/// <param name="box">The box to test.</param>
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/// <returns><c>true</c> if the bounding box intersects with another box, <c>false</c> otherwise.</returns>
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public bool Intersects(BoundingBox box)
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{
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return
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Min.X <= box.Max.X && Max.X >= box.Min.X &&
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Min.Y <= box.Max.Y && Max.Y >= box.Min.Y &&
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Min.Z <= box.Max.Z && Max.Z >= box.Min.Z;
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}
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/// <summary>
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/// Determines whether the bounding box intersects with a ray.
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/// </summary>
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/// <param name="ray">The ray to test.</param>
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/// <returns><c>true</c> if the box intersects with the ray, <c>false</c> otherwise.</returns>
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public bool IntersectRay(Ray ray)
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{
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double distance;
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return IntersectRay(ray, out distance);
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}
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/// <summary>
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/// Determines whether the bounding box intersects with a ray.
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/// </summary>
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/// <param name="ray">The ray to test.</param>
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/// <param name="distance">The calculated distance from the origin of the ray to the box along the ray.</param>
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/// <returns><c>true</c> if the box intersects with the ray, <c>false</c> otherwise.</returns>
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public bool IntersectRay(Ray ray, out double distance)
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{
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Point dirFrac = new Point(
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1f / ray.Direction.X,
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1f / ray.Direction.Y,
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1f / ray.Direction.Z
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);
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double t1 = (Min.X - ray.Origin.X) * dirFrac.X;
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double t2 = (Max.X - ray.Origin.X) * dirFrac.X;
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double t3 = (Min.Y - ray.Origin.Y) * dirFrac.Y;
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double t4 = (Max.Y - ray.Origin.Y) * dirFrac.Y;
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double t5 = (Min.Z - ray.Origin.Z) * dirFrac.Z;
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double t6 = (Max.Z - ray.Origin.Z) * dirFrac.Z;
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double tmin = Math.Max(Math.Max(Math.Min(t1, t2), Math.Min(t3, t4)), Math.Min(t5, t6));
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double tmax = Math.Min(Math.Min(Math.Max(t1, t2), Math.Max(t3, t4)), Math.Max(t5, t6));
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// if tmax < 0, ray (line) is intersecting AABB, but the whole AABB is behind us
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if (tmax < 0)
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{
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distance = tmax;
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return false;
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}
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// if tmin > tmax, ray doesn't intersect AABB
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if (tmin > tmax)
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{
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distance = tmax;
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return false;
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}
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distance = tmin;
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return true;
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}
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/// <summary>
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/// Determines whether the bounding box intersects with a plane.
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/// </summary>
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/// <param name="plane">The plane to test.</param>
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/// <param name="distance">The minimum distance from the bounding box to the plane .</param>
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/// <returns><c>true</c> if the box intersects with the plane, <c>false</c> otherwise.</returns>
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public bool IntersectPlane(Plane plane, out double distance)
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{
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// https://gdbooks.gitbooks.io/3dcollisions/content/Chapter2/static_aabb_plane.html
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// Compute the projection interval radius of b onto L(t) = b.c + t * p.n
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double r = Extents.X * Math.Abs(plane.Normal.X) + Extents.Y * Math.Abs(plane.Normal.Y) + Extents.Z * Math.Abs(plane.Normal.Z);
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// Compute distance of box center from plane
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double s = Point.Dot(plane.Normal, Center) + plane.D;
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// Intersection occurs when distance s falls within [-r,+r] interval
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if (Math.Abs(s) <= r)
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{
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distance = 0;
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return true;
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}
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else
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{
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if (s > 0) distance = s - r;
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else distance = s + r;
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return false;
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}
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}
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/// <summary>
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/// Returns a hash code for this instance.
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/// </summary>
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/// <returns>A hash code for this instance, suitable for use in hashing algorithms and data structures like a hash table.</returns>
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public override int GetHashCode()
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{
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return Center.GetHashCode() ^ Extents.GetHashCode() << 2;
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}
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/// <summary>
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/// Determines whether the specified object as a <see cref="BoundingBox" /> is equal to this instance.
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/// </summary>
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/// <param name="other">The <see cref="BoundingBox" /> object to compare with this instance.</param>
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/// <returns><c>true</c> if the specified box is equal to this instance; otherwise, <c>false</c>.</returns>
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public override bool Equals(object other)
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{
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bool result;
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if (!(other is BoundingBox))
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{
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result = false;
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}
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else
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{
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BoundingBox box = (BoundingBox)other;
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result = (Center.Equals(box.Center) && Extents.Equals(box.Extents));
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}
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return result;
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}
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/// <summary>
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/// Returns a nicely formatted string for this bounding box.
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/// </summary>
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public override string ToString()
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{
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return String.Format("Center: {0}, Extents: {1}",
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Center,
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Extents
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);
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}
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/// <summary>
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/// Returns a nicely formatted string for this bounding box.
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/// </summary>
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/// <param name="format">The format for the center and the extent.</param>
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public string ToString(string format)
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{
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return String.Format("Center: {0}, Extents: {1}",
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Center.ToString(format),
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Extents.ToString(format)
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);
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}
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/// <summary>
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/// Determines whether two bounding boxes are equal.
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/// </summary>
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/// <param name="lhs">The first box.</param>
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/// <param name="rhs">The second box.</param>
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public static bool operator ==(BoundingBox lhs, BoundingBox rhs)
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{
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return lhs.Center == rhs.Center && lhs.Extents == rhs.Extents;
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}
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/// <summary>
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/// Determines whether two bounding boxes are different.
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/// </summary>
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/// <param name="lhs">The first box.</param>
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/// <param name="rhs">The second box.</param>
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public static bool operator !=(BoundingBox lhs, BoundingBox rhs)
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{
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return !(lhs == rhs);
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}
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}
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}
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