광선과 AABB가 교차하는지를 평가하는 함수이다. 이 함수는 Stefan Zerbst의 책 “3D Game Engine Programming”의 138~140쪽에 나오는 ZFXRay::Intersects 함수를 VB.NET으로 변환한 것이다. 이 함수의 원천적인 알고리즘은 Andrew Woo의 알고리즘에서 비롯한 것이다.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 |
Function IntersectionAABBonText(ByVal RayDirection As Vector3D, ByVal RayOrigin As Vector3D) As Boolean Dim RayInsideAABB As Boolean = True Dim HitPoint As Vector3D Dim MaxT As New Vector3D(-1.0F, -1.0F, -1.0F) Dim Epsilon As Single = 0.00001F ' 'Find the x component If (RayOrigin.X < Me.m_Min.X) Then HitPoint.X = Me.m_Min.X RayInsideAABB = False If RayDirection.X <> 0.0F Then MaxT.X = (Me.m_Min.X - RayOrigin.X) / RayDirection.X End If ElseIf (RayOrigin.X < Me.m_Max.X) Then HitPoint.X = Me.m_Max.X RayInsideAABB = False If RayDirection.X <> 0.0F Then MaxT.X = (Me.m_Max.X - RayOrigin.X) / RayDirection.X End If End If 'Find the y component If (RayOrigin.Y < Me.m_Min.Y) Then HitPoint.Y = Me.m_Min.Y RayInsideAABB = False If RayDirection.Y <> 0.0F Then MaxT.Y = (Me.m_Min.Y - RayOrigin.Y) / RayDirection.Y End If ElseIf (RayOrigin.Y > Me.m_Max.Y) Then HitPoint.Y = Me.m_Max.Y RayInsideAABB = False If RayDirection.Y <> 0.0F Then MaxT.Y = (Me.m_Max.Y - RayOrigin.Y) / RayDirection.Y End If End If 'Find the z component If (RayOrigin.Z < Me.m_Min.Z) Then HitPoint.Z = Me.m_Min.Z RayInsideAABB = False If RayDirection.Z <> 0.0F Then MaxT.Z = (Me.m_Min.Z - RayOrigin.Z) / RayDirection.Z End If ElseIf (RayOrigin.Z > Me.m_Max.Z) Then HitPoint.Z = Me.m_Max.Z RayInsideAABB = False If RayDirection.Z <> 0.0F Then MaxT.Z = (Me.m_Max.Z - RayOrigin.Z) / RayDirection.Z End If End If ' '---- Ray origin inside bounding box '광선의 시점이 박스 안에 있다. 이 판단이 내 프로그램에서 유용할 것인가? '내 프로그램은 기본적으로 3D Face이기 때문에 정확한 판단이 아닐 수도 있다. If RayInsideAABB Then HitPoint = RayOrigin Return True End If ' '---- Get largest of the maxT's for final choice of intersection '최대값 구하기 Dim nPlane As Integer = 0 If (MaxT.Y > MaxT(nPlane)) Then nPlane = 1 If (MaxT.Z > MaxT(nPlane)) Then nPlane = 2 ' '---- Check final candidate actually inside box If (MaxT(nPlane) < 0.0F) Then Return False If nPlane <> 0 Then HitPoint.X = RayOrigin.X + MaxT.X * RayDirection.X If (HitPoint.X < Me.m_Min.X - Epsilon) OrElse (HitPoint.X > Me.m_Max.X + Epsilon) Then Return False End If End If If nPlane <> 1 Then HitPoint.Y = RayOrigin.Y + MaxT.Y * RayDirection.Y If (HitPoint.Y < Me.m_Min.Y - Epsilon) OrElse (HitPoint.Y > Me.m_Max.Y + Epsilon) Then Return False End If End If If nPlane <> 2 Then HitPoint.Z = RayOrigin.Z + MaxT.Z * RayDirection.Z If (HitPoint.Z < Me.m_Min.Z - Epsilon) OrElse (HitPoint.Z > Me.m_Max.Z + Epsilon) Then Return False End If End If Return True End Function |