DirectX 中的 XMVECTOR

Question

Sorry for the dumb question .... but why this does not work ? To show the problem I wrote this simple code:

#include <windows.h> 
#include <DirectXMath.h>
#include <DirectXPackedVector.h>
#include <iostream>
using namespace std;
using namespace DirectX;
using namespace DirectX::PackedVector;

int main()
{
XMVECTOR c = XMVECTORSet(3.0f, 3.0f, 3.0f, 3.0f);

return 0;
}

VS answers "error C3861: 'XMVECTORSet': identifier not found"

Answer 1

You should use XMVectorSet instead of XMVECTORSet (This function does not exist)

Function definition on msdn

Answer 2

There are a number of ways to initialize a vectorized-constant for DirectXMath. XMVectorSet is best when the parameters are float variables not literal values.

XMVECTOR c = XMVectorSet( 3.f, 3.f, 3.f, .3f );

In the case of a literal constant, you are better off using:

const XMVECTORF32 c = { 3.f, 3.f, 3.f, 3.f };

clang will want you to write it as: const XMVECTORF32 c = { { { 3.f, 3.f, 3.f, 3f.f } } }; if you have -Wmissing-braces enabled.

Other options (again, not the best for literal values, but better for variables):

XMVECTOR c = XMVectorReplicate( 3.f );

float x = 3.f;
XMVECTOR c = XMVectorReplicatePtr(&x);

const XMVECTORF32 t = { 1.f, 2.f, 3.f, 4.f };
XMVECTOR c = XMVectorSplatZ(t);

The DirectXMath Programmer's Guide is a short read, and it covers a lot of use cases.

If you are new to DirectXMath, you should consider using the SimpleMath wrapper types for DirectXMath that is included in DirectX Tool Kit for DX11 / DX12 .