Re: DirectX API and my classes

From:
"Giovanni Dicanio" <giovanni.dicanio@invalid.com>
Newsgroups:
microsoft.public.vc.language
Date:
Fri, 9 May 2008 11:28:56 +0200
Message-ID:
<O9SQ$cbsIHA.5268@TK2MSFTNGP06.phx.gbl>
"Jack" <jl@knight.com> ha scritto nel messaggio
news:OKlcB$asIHA.4876@TK2MSFTNGP02.phx.gbl...

I am getting a little bit puzzled
There is a class in Direct3D called D3DXLoadMeshFromHierarchy
which takes a LPD3DXFRAME as the sixth
parameter.


I think that D3DXLoadMeshFromHierarchy is a function (or method) but not a
class...

However, I failed to find documentation about that.

And my question is
if I derived a new class with additional attributes
from D3DXFRAME say Derived_Frame

How can I make D3DXLoadMeshFromHierarchy
choose my derived class Derived_Frame instead of LPD3DXFRAME


If LPD3DXFRAME is an output parameter, i.e. if the aforementioned function
"builds" an instance of D3D frame class (I think so), then you must use a
pointer of type LPD3DXFRAME, not a pointer to some derived class.

Moroever, I think that D3D uses COM for its components (COM interfaces), so
it might be that this LPD3DXFRAME is a pointer to some COM interface (like
ID3DXFrame...), and deriving classes from COM interfaces is not trivial (you
should derive a new interface from an existing COM interface, etc. ...)

Instead, you can define a new C++ class, and add a member variable of type
LPD3DXFRAME, and init that using the value returned as output parameter from
D3DXLoadMeshFrom...

 class CMyFrame
 {
  ...

   //
   // Init that pointer (data member) with
   // the return value of
   // D3DXLoadMeshFromHierarchy
   //
   LPD3DXFRAME m_pD3DXFrame;

   ...
   other data members
   ...
 };

HTH,
Giovanni

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