BoundingFrustum CreateFromMatrix option for RH coordinates

Author: walbourn

Inc/DirectXCollision.h

@@ -258,7 +258,7 @@ namespace DirectX
             : Origin(_Origin), Orientation(_Orientation),
             RightSlope(_RightSlope), LeftSlope(_LeftSlope), TopSlope(_TopSlope), BottomSlope(_BottomSlope),
             Near(_Near), Far(_Far) {}
-        BoundingFrustum(_In_ CXMMATRIX Projection) noexcept;
+        BoundingFrustum(_In_ CXMMATRIX Projection, bool rhcoords = false) noexcept;
 
         // Methods
         void    XM_CALLCONV     Transform(_Out_ BoundingFrustum& Out, _In_ FXMMATRIX M) const noexcept;
@@ -298,7 +298,7 @@ namespace DirectX
         // Create 6 Planes representation of Frustum
 
     // Static methods
-        static void     XM_CALLCONV     CreateFromMatrix(_Out_ BoundingFrustum& Out, _In_ FXMMATRIX Projection) noexcept;
+        static void     XM_CALLCONV     CreateFromMatrix(_Out_ BoundingFrustum& Out, _In_ FXMMATRIX Projection, bool rhcoords = false) noexcept;
     };
 
     //-----------------------------------------------------------------------------

Inc/DirectXCollision.inl

@@ -2818,9 +2818,9 @@ inline void BoundingOrientedBox::CreateFromPoints(BoundingOrientedBox& Out, size
  ****************************************************************************/
 
 _Use_decl_annotations_
-inline BoundingFrustum::BoundingFrustum(CXMMATRIX Projection) noexcept
+inline BoundingFrustum::BoundingFrustum(CXMMATRIX Projection, bool rhcoords) noexcept
 {
-    CreateFromMatrix(*this, Projection);
+    CreateFromMatrix(*this, Projection, rhcoords);
 }
 
 
@@ -4252,7 +4252,7 @@ inline void BoundingFrustum::GetPlanes(XMVECTOR* NearPlane, XMVECTOR* FarPlane,
 // constructed frustum to be incorrect.
 //-----------------------------------------------------------------------------
 _Use_decl_annotations_
-inline void XM_CALLCONV BoundingFrustum::CreateFromMatrix(BoundingFrustum& Out, FXMMATRIX Projection) noexcept
+inline void XM_CALLCONV BoundingFrustum::CreateFromMatrix(BoundingFrustum& Out, FXMMATRIX Projection, bool rhcoords) noexcept
 {
     // Corners of the projection frustum in homogenous space.
     static XMVECTORF32 HomogenousPoints[6] =
@@ -4296,8 +4296,16 @@ inline void XM_CALLCONV BoundingFrustum::CreateFromMatrix(BoundingFrustum& Out,
     Points[4] = XMVectorMultiply(Points[4], XMVectorReciprocal(XMVectorSplatW(Points[4])));
     Points[5] = XMVectorMultiply(Points[5], XMVectorReciprocal(XMVectorSplatW(Points[5])));
 
-    Out.Near = XMVectorGetZ(Points[4]);
-    Out.Far = XMVectorGetZ(Points[5]);
+    if (rhcoords)
+    {
+        Out.Near = XMVectorGetZ(Points[5]);
+        Out.Far = XMVectorGetZ(Points[4]);
+    }
+    else
+    {
+        Out.Near = XMVectorGetZ(Points[4]);
+        Out.Far = XMVectorGetZ(Points[5]);
+    }
 }