Question

Using the D3DX library that is a part of directX, specifically directx9 in this case, I’m wondering if it’s safe to use the same matrix (or vector etc) for input and ouput

D3DXMATRIX mat;
D3DXMatrixInverse(&mat, NULL, &mat);

I’ve been avoiding doing so, assuming that it would result in bad things happening when parts of the array got partly overwritten as results are calculated but I see an awful lot of code around that does exactly this.

A brief test indicates that it seems to work ok, so I’m assuming that the D3DX functions take a copy where necessary of the input data, or some other method to ensure that this works ok, but I can’t find it documented anywhere so I’m reluctant to rely on it working.

Is there any official statement on using the functions like this?

Answer 1

Yes, it is. From msdn:

Each of the functions can take the same object as the passed [in] and returned [out] parameters