text: //
  // Copyright (c) 2008-2020 the Urho3D project.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  //
  
  #pragma once
  
  #include "../Math/Vector3.h"
  #include "../Math/Matrix3x4.h"
  
  namespace Urho3D
  {
  
  class BoundingBox;
  class Frustum;
  class Plane;
  class Sphere;
  
  /// Infinite straight line in three-dimensional space.
  /// @allfloats
  class URHO3D_API Ray
  {
  public:
      /// Construct a degenerate ray with zero origin and direction.
      Ray() noexcept = default;
  
      /// Construct from origin and direction. The direction will be normalized.
      Ray(const Vector3& origin, const Vector3& direction) noexcept
      {
          Define(origin, direction);
      }
  
      /// Copy-construct from another ray.
      Ray(const Ray& ray) noexcept = default;
  
      /// Assign from another ray.
      Ray& operator =(const Ray& rhs) noexcept = default;
  
      /// Check for equality with another ray.
      bool operator ==(const Ray& rhs) const { return origin_ == rhs.origin_ && direction_ == rhs.direction_; }
  
      /// Check for inequality with another ray.
      bool operator !=(const Ray& rhs) const { return origin_ != rhs.origin_ || direction_ != rhs.direction_; }
  
      /// Define from origin and direction. The direction will be normalized.
      void Define(const Vector3& origin, const Vector3& direction)
      {
          origin_ = origin;
          direction_ = direction.Normalized();
      }
  
      /// Project a point on the ray.
      Vector3 Project(const Vector3& point) const
      {
          Vector3 offset = point - origin_;
          return origin_ + offset.DotProduct(direction_) * direction_;
      }
  
      /// Return distance of a point from the ray.
      float Distance(const Vector3& point) const
      {
          Vector3 projected = Project(point);
          return (point - projected).Length();
      }
  
      /// Return closest point to another ray.
      Vector3 ClosestPoint(const Ray& ray) const;
      /// Return hit distance to a plane, or infinity if no hit.
      float HitDistance(const Plane& plane) const;
      /// Return hit distance to a bounding box, or infinity if no hit.
      float HitDistance(const BoundingBox& box) const;
      /// Return hit distance to a frustum, or infinity if no hit. If solidInside parameter is true (default) rays originating from inside return zero distance, otherwise the distance to the closest plane.
      float HitDistance(const Frustum& frustum, bool solidInside = true) const;
      /// Return hit distance to a sphere, or infinity if no hit.
      float HitDistance(const Sphere& sphere) const;
      /// Return hit distance to a triangle, or infinity if no hit. Optionally return hit normal and hit barycentric coordinate at intersect point.
      float HitDistance(const Vector3& v0, const Vector3& v1, const Vector3& v2, Vector3* outNormal = nullptr, Vector3* outBary = nullptr) const;
      /// Return hit distance to non-indexed geometry data, or infinity if no hit. Optionally return hit normal and hit uv coordinates at intersect point.
      float HitDistance
          (const void* vertexData, unsigned vertexStride, unsigned vertexStart, unsigned vertexCount, Vector3* outNormal = nullptr,
              Vector2* outUV = nullptr, unsigned uvOffset = 0) const;
      /// Return hit distance to indexed geometry data, or infinity if no hit. Optionally return hit normal and hit uv coordinates at intersect point.
      float HitDistance(const void* vertexData, unsigned vertexStride, const void* indexData, unsigned indexSize, unsigned indexStart,
          unsigned indexCount, unsigned &subObjectElementIndex, Vector3* outNormal = nullptr, Vector2* outUV = nullptr, unsigned uvOffset = 0) const;
      /// Return whether ray is inside non-indexed geometry.
      bool InsideGeometry(const void* vertexData, unsigned vertexSize, unsigned vertexStart, unsigned vertexCount) const;
      /// Return whether ray is inside indexed geometry.
      bool InsideGeometry(const void* vertexData, unsigned vertexSize, const void* indexData, unsigned indexSize, unsigned indexStart,
          unsigned indexCount) const;
      /// Return transformed by a 3x4 matrix. This may result in a non-normalized direction.
      Ray Transformed(const Matrix3x4& transform) const;
  
      /// Ray origin.
      Vector3 origin_;
      /// Ray direction.
      Vector3 direction_;
  };
  
  }
  