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Bitmap background with OpenGL objects in front

Posted on 1997-04-28
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Last Modified: 2008-03-10
Hi!

I have a bitmap (CBitmap) I want to use as a background when drawing OpenGL
objects on top of it (Visual C++ 4.0 in Windows 95), but I don't get it
right...
The OnDraw function works fine when drawing just the OpenGL objects, but
when trying to draw a background first, the screen just flash between the
OpenGL drawing and the background... (terrible!)
I use the following call to draw the background:

pDC->BitBlt(0, 0, m_cxWnd, m_cyWnd, m_pDCMem, 0, 0, SRCCOPY);

m_pDCMem is a DCD and gets a bitmap object from:  m_pDCMem->SelectObject(
pBM),  (pBM is a CBitmap object)

Do I have to use an OpenGL command to draw the background bitmap or is
there another solution?

Thanks!!
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Question by:Krafer
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1 Comment
 
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Accepted Solution

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RONSLOW earned 200 total points
ID: 1163014
Don't use double buffering in OpenGL if you wish to mix GDI (eg BitBlt) with OpenGL.

If you still want the smoothness of double buffering, try rendering into an off-screen bitmap into which you first draw your background image (using BitBlt).

Using an off-screen bitmap for your rendering also gives you the advantage that you can print the view (you cannot directly render to a pritner device context)

For further info, you can eMail me on Roger_Onslow@compsys.com.au
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