XMVectorSelect function (directxmath.h)

Article
07/12/2022

Performs a per-component selection between two input vectors and returns the resulting vector.

Syntax

XMVECTOR XM_CALLCONV XMVectorSelect(
  [in] FXMVECTOR V1,
  [in] FXMVECTOR V2,
  [in] FXMVECTOR Control
) noexcept;

Parameters

[in] V1

First vector to compare.

[in] V2

Second vector to compare.

[in] Control

Vector mask used to select a vector component from either V1 or V2. If a component of Control is zero, the returned vector's corresponding component will be the first vector's component. If a component of Control is 0xFF, the returned vector's corresponding component will be the second vector's component. For full details on how the vector mask works, see the "Remarks".

Typically, the vector used for Control will be either the output of a vector comparison function (such as XMVectorEqual, XMVectorLess, or XMVectorGreater) or it will be the output of XMVectorSelectControl.

Return value

Returns the result of the per-component selection.

Remarks

If any given bit of Control is set, the corresponding bit from V2 is used, otherwise, the corresponding bit from V1 is used. The following pseudocode demonstrates the operation of the function:

XMVECTOR Result;

Result.u[0] = (V1.u[0] & ~Control.u[0]) | (V2.u[0] & Control.u[0]);
Result.u[1] = (V1.u[1] & ~Control.u[1]) | (V2.u[1] & Control.u[1]);
Result.u[2] = (V1.u[2] & ~Control.u[2]) | (V2.u[2] & Control.u[2]);
Result.u[3] = (V1.u[3] & ~Control.u[3]) | (V2.u[3] & Control.u[3]);

return Result;

Manual construction of a control vector is not necessary. There are two simple ways of constructing an appropriate control vector:

Using the XMVectorSelectControl function to construct a control vector.
See Using XMVectorSelect and XMVectorSelectControl for a demonstration of how this function can be used.
The control vector can be constructed using the XM_SELECT_[0,1] constant (see DirectXMath Library Constants). As an example, in pseudo-code, an instance of Control with the elements:
```
   Control = { XM_SELECT_0,   XM_SELECT_1,   XM_SELECT_0,   XM_SELECT_1 }
```
would return a vector Result with the following components of V1 and V2
```
   Result = { V1.X,  V2.Y,   V1.Z,   V2.W }
```

Platform Requirements

Microsoft Visual Studio 2010 or Microsoft Visual Studio 2012 with the Windows SDK for Windows 8. Supported for Win32 desktop apps, Windows Store apps, and Windows Phone 8 apps.

Requirements

Requirement	Value
Target Platform	Windows
Header	directxmath.h (include DirectXMath.h)

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