Axiom.SceneManagers.PortalConnected.Portal.getDerivedCorner C# (CSharp) Method

		public Vector3 getDerivedCorner( int index )
		{
			return mDerivedCorners[ index ];
		}
		// Get the direction of the portal in world coordinates (assumes  it is up-to-date)

		/// <summary>
		///     IsObjectVisible() function for portals.
		/// </summary>
		/// <remarks>
		///     Everything needs to be updated spatially before this function is
		///     called including portal corners, frustum planes, etc.
		/// </remarks>
		/// <param name="portal">
		///     The <see cref="Portal"/> to check visibility against.
		/// </param>
		/// <param name="culledBy">
		///     The <see cref="FrustumPlane"/> that the Portal is in.
		/// </param>
		/// <returns>
		///     true if the Portal is visible.
		/// </returns>
		public bool IsObjectVisible( Portal portal, out FrustumPlane culledBy )
		{
			culledBy = FrustumPlane.None;

			// if portal isn't open, it's not visible
			if ( !portal.IsOpen )
			{
				return false;
			}

			// check the extra frustum first
			if ( !this.extraCullingFrustum.IsObjectVisible( portal ) )
			{
				return false;
			}

			// if portal is of type AABB or Sphere, then use simple bound check against planes
			if ( portal.Type == PORTAL_TYPE.PORTAL_TYPE_AABB )
			{
				var aabb = new AxisAlignedBox( portal.getDerivedCorner( 0 ), portal.getDerivedCorner( 1 ) );
				return base.IsObjectVisible( aabb, out culledBy );
			}
			else if ( portal.Type == PORTAL_TYPE.PORTAL_TYPE_SPHERE )
			{
				return base.IsObjectVisible( portal.getDerivedSphere(), out culledBy );
			}

			// check if the portal norm is facing the camera
			Vector3 cameraToPortal = portal.getDerivedCP() - DerivedPosition;
			Vector3 portalDirection = portal.getDerivedDirection();
			Real dotProduct = cameraToPortal.Dot( portalDirection );
			if ( dotProduct > 0 )
			{
				// portal is faced away from camera
				return false;
			}
			// check against regular frustum planes
			bool visible_flag;
			if ( null != CullFrustum )
			{
				// For each frustum plane, see if all points are on the negative side
				// If so, object is not visible
				// NOTE: We skip the NEAR plane (plane #0) because Portals need to
				// be visible no matter how close you get to them.

				for ( int plane = 1; plane < 6; ++plane )
				{
					// set the visible flag to false
					visible_flag = false;
					// Skip far plane if infinite view frustum
					if ( (FrustumPlane)plane == FrustumPlane.Far && _farDistance == 0 )
					{
						continue;
					}

					// we have to check each corner of the portal
					for ( int corner = 0; corner < 4; corner++ )
					{
						PlaneSide side = CullFrustum.FrustumPlanes[ plane ].GetSide( portal.getDerivedCorner( corner ) );
						if ( side != PlaneSide.Negative )
						{
							visible_flag = true;
						}
					}
					// if the visible_flag is still false, then this plane
					// culled all the portal points
					if ( visible_flag == false )
					{
						// ALL corners on negative side therefore out of view
						if ( culledBy != FrustumPlane.None )
						{
							culledBy = (FrustumPlane)plane;
						}
						return false;
					}
				}
			}
			else
			{
				// Make any pending updates to the calculated frustum planes
				UpdateFrustumPlanes();

				// For each frustum plane, see if all points are on the negative side
				// If so, object is not visible
				// NOTE: We skip the NEAR plane (plane #0) because Portals need to
				// be visible no matter how close you get to them.
				// BUGBUG: This can cause a false positive situation when a portal is
				// behind the camera but close.  This could be fixed by having another
				// culling plane at the camera location with normal same as camera direction.
				for ( int plane = 1; plane < 6; ++plane )
				{
					// set the visible flag to false
					visible_flag = false;
					// Skip far plane if infinite view frustum
					if ( (FrustumPlane)plane == FrustumPlane.Far && _farDistance == 0 )
					{
						continue;
					}

					// we have to check each corner of the portal
					for ( int corner = 0; corner < 4; corner++ )
					{
						PlaneSide side = _planes[ plane ].GetSide( portal.getDerivedCorner( corner ) );
						if ( side != PlaneSide.Negative )
						{
							visible_flag = true;
						}
					}
					// if the visible_flag is still false, then this plane
					// culled all the portal points
					if ( visible_flag == false )
					{
						// ALL corners on negative side therefore out of view
						if ( culledBy != FrustumPlane.None )
						{
							culledBy = (FrustumPlane)plane;
						}
						return false;
					}
				}
			}
			// no plane culled all the portal points and the norm
			// was facing the camera, so this portal is visible
			return true;
		}