Minor comment and parameter update to make it clear XMPlaneTransform(Stream) expects the inverse transpose

Author: walbourn

Inc/DirectXMath.h

@@ -1559,11 +1559,15 @@ namespace DirectX
     XMVECTOR    XM_CALLCONV     XMPlaneNormalize(FXMVECTOR P) noexcept;
     XMVECTOR    XM_CALLCONV     XMPlaneIntersectLine(FXMVECTOR P, FXMVECTOR LinePoint1, FXMVECTOR LinePoint2) noexcept;
     void        XM_CALLCONV     XMPlaneIntersectPlane(_Out_ XMVECTOR* pLinePoint1, _Out_ XMVECTOR* pLinePoint2, _In_ FXMVECTOR P1, _In_ FXMVECTOR P2) noexcept;
-    XMVECTOR    XM_CALLCONV     XMPlaneTransform(FXMVECTOR P, FXMMATRIX M) noexcept;
-    XMFLOAT4* XM_CALLCONV     XMPlaneTransformStream(_Out_writes_bytes_(sizeof(XMFLOAT4) + OutputStride * (PlaneCount - 1)) XMFLOAT4* pOutputStream,
+
+    // Transforms a plane given an inverse transpose matrix
+    XMVECTOR    XM_CALLCONV     XMPlaneTransform(FXMVECTOR P, FXMMATRIX ITM) noexcept;
+
+    // Transforms an array of planes given an inverse transpose matrix
+    XMFLOAT4*   XM_CALLCONV     XMPlaneTransformStream(_Out_writes_bytes_(sizeof(XMFLOAT4) + OutputStride * (PlaneCount - 1)) XMFLOAT4* pOutputStream,
         _In_ size_t OutputStride,
         _In_reads_bytes_(sizeof(XMFLOAT4) + InputStride * (PlaneCount - 1)) const XMFLOAT4* pInputStream,
-        _In_ size_t InputStride, _In_ size_t PlaneCount, _In_ FXMMATRIX M) noexcept;
+        _In_ size_t InputStride, _In_ size_t PlaneCount, _In_ FXMMATRIX ITM) noexcept;
 
     XMVECTOR    XM_CALLCONV     XMPlaneFromPointNormal(FXMVECTOR Point, FXMVECTOR Normal) noexcept;
     XMVECTOR    XM_CALLCONV     XMPlaneFromPoints(FXMVECTOR Point1, FXMVECTOR Point2, FXMVECTOR Point3) noexcept;

Inc/DirectXMathMisc.inl

@@ -1217,39 +1217,39 @@ inline void XM_CALLCONV XMPlaneIntersectPlane
 inline XMVECTOR XM_CALLCONV XMPlaneTransform
 (
     FXMVECTOR P,
-    FXMMATRIX M
+    FXMMATRIX ITM
 ) noexcept
 {
     XMVECTOR W = XMVectorSplatW(P);
     XMVECTOR Z = XMVectorSplatZ(P);
     XMVECTOR Y = XMVectorSplatY(P);
     XMVECTOR X = XMVectorSplatX(P);
 
-    XMVECTOR Result = XMVectorMultiply(W, M.r[3]);
-    Result = XMVectorMultiplyAdd(Z, M.r[2], Result);
-    Result = XMVectorMultiplyAdd(Y, M.r[1], Result);
-    Result = XMVectorMultiplyAdd(X, M.r[0], Result);
+    XMVECTOR Result = XMVectorMultiply(W, ITM.r[3]);
+    Result = XMVectorMultiplyAdd(Z, ITM.r[2], Result);
+    Result = XMVectorMultiplyAdd(Y, ITM.r[1], Result);
+    Result = XMVectorMultiplyAdd(X, ITM.r[0], Result);
     return Result;
 }
 
 //------------------------------------------------------------------------------
 _Use_decl_annotations_
 inline XMFLOAT4* XM_CALLCONV XMPlaneTransformStream
 (
-    XMFLOAT4* pOutputStream,
+    XMFLOAT4*       pOutputStream,
     size_t          OutputStride,
     const XMFLOAT4* pInputStream,
     size_t          InputStride,
     size_t          PlaneCount,
-    FXMMATRIX       M
+    FXMMATRIX       ITM
 ) noexcept
 {
     return XMVector4TransformStream(pOutputStream,
         OutputStride,
         pInputStream,
         InputStride,
         PlaneCount,
-        M);
+        ITM);
 }
 
 //------------------------------------------------------------------------------