Why the Displacement Amount is -1 when using vector displacement from mudbox

[C1_mill]

I have successfully export a vector displacement from Mudbox 2014 SP1 using following setting
"Smooth Target Models" on
"Smooth Target UVs" off
"Use Creases & Hard Edges" on
"Smooth Source Models" on
Image Size 2048X2048
Antialiasing 2X
Vector Space "Absolute Tangent"
32bit float point EXR

Then in Maya 2014 SP2, i import the object into Maya, add Vray's Subsivision, Subdivision and Displacement Quality, and Displacment control attributes. I can get the same shape and form like Mudbox with vector displacement but i need to set displacement amount to -1.0. If i set the displacement amount to 1.00, the result will become invert like. The shape which should be push in will become pull out, pull out will become push in. Why the displacement amount is -1.0

Here is my setting

"Render as subdivision surface" turn on
"Subdivide UVs at borders" turn off
"Subdivide UVs" turn off (I turn off in Mudbox)
"Override Global Settings" turn on
"View Dependent" turn on
"Edge Length" 2.0
"Max subdivs" 10
Displacement Type = "Vector Displacement (absolute)"
Displacement Amount = -1.0 (Yes, -1.0)
Dispalcement Shift = 0.0
Keep Continuity turn on
Fliter Texture turn off
Displacement bound = "Automatic"

In the file texture node
Filter type = mipmap
Filter = 0.003
Allow negative colors turn on

[vlado]

Is it possible that your UVs are flipped compared to the normal surface orientation?

Best regards,
Vlado

[C1_mill]

I am so careless!!!.....Thanks!