two devices rendering the same scene

I want to render the same scene with the same objects, as seen from two 
perspectives.
Since a device takes a window, it seems I mush have a device pr view (pr. 
window), but since vertexarrays are created relative to a devgice, does this 
mean that i must dumplicate my scene data? One copy for each device?

How can i have scene data which is common to the two devices? 

The easy way is to use one window, and render into two different 
viewports on it.

	Eyal

> The easy way is to use one window, and render into two different viewports 

That would be an idea. Didn't consider that.
What would be the not-easy way? 

Playing multi-monitor. And here, you too have an easy way and a hard way..
The easy way is to use multi-head capabilities :)

Wessam Bahnassi
Microsoft DirectX MVP,
Lead Programmer
In|Framez

> Playing multi-monitor. And here, you too have an easy way and a hard way..

Ok, so in reality the solution is to actually create two devices and 
duplicate the objects to both devices.
I have no great need for speed, so I guess it will work ok.
Was meerly wondering if I was overlooking some feature in dx which made it 
easy to have to views of the same scene. 

Just to be sure, since you haven't explicitly stated such, are you going to 
be rendering the two views on separate monitors?  Otherwise there shouldn't 
be a need for two devices to render to separate windows on the same monitor.

To render multiple views to separate windows you can use 
IDirect3DDevice9::CreateAdditionalSwapChain to create additional back buffer 
chains attached to different windows.  To render each view you would get the 
back buffer from the swap chain, set it as the device's render target, 
render the scene, and call IDirect3DSwapChain9::Present() to present the 
scene to the associated window.

-- 
Robert Dunlop
The X-Zone
 http://www.**--****.com/ 
Microsoft DirectX MVP
-------------
The opinions expressed in this message are my own personal views and do not 
reflect the official views of the Microsoft Corporation.
The MVP program does not constitute employment or contractual obligation 
with Microsoft. 

> Just to be sure, since you haven't explicitly stated such, are you going 

One monitor. As many modelling tools have four views: x,y,z and perspective.
Currently I only need two views.

Mutiple swap chains will be preferred here (as Robert said). You can also 
have one big window that you draw to its different parts by using 
SetViewport() to limit your output to different rects. But here, you need to 
render to all views before you can present the next frame, whilst in 
separate swap chains you can present wach one independently.

Wessam Bahnassi
Microsoft DirectX MVP,
Lead Programmer
In|Framez

> Mutiple swap chains will be preferred here (as Robert said). You can also 

I will look at swap chains. For now I will just go with the change of 
viewports. It will work for now.
Thanks for the help. 

You can render to a second window by putting the window handle in the
present call.
Just use 2 cameras, use one for the default device window and the other for
the other window so they can have different views.

You dont need another device, and another viewport is optional, depending on
the size of area you want to see in the other window.

pDevice->SetTransform(D3DTS_VIEW, &m_mCamera2);
pDevice->Clear(blah blah bla);
pDevice->BeginScene();
pStuff->Render();
pDevice->EndScene;
pDevice->Present(NULL, NULL, g_hWnd2, NULL);

Works for me anyway.
Callum.





also
need

> You dont need another device, and another viewport is optional, depending 

That was easy. I simply didn't realize that the present method took a window 
handle to override the one given to the device.
That was really all I needed. One scene, one device, two cameras each with a 
window and viola!
Thanks a lot. Now I just wonder if I should consider starting lines with 
something other than "Tha" :-) 

This way, all windows should have the same client area size, otherwise 
StretchRect()s will be involved (unless you fix things up with 
SetViewport()).

Wessam Bahnassi
Microsoft DirectX MVP,
Lead Programmer
In|Framez

"Wessam Bahnassi" < XXXX@XXXXX.COM >

What do you mean by "StretchRect will be involved"? I use .net and threw in 
two pictureboxes and renderes to them. One was smaller and more elongated 
that the other, and both showed what was expected.
That is.. The one box with i had measured my aspect ration (in perspective) 
relative to, was perfect. The other had a faulty aspectratio, but that is 
something that the matrix stack will handle.

Is there a problem, I need to know about? 

> What do you mean by "StretchRect will be involved"? I use .net and threw 

I think i know the problem now. It didn't turn up before, but now I tried 
creating a device with null as window handle. It should be valid for a 
windowed device, but it will not allow it(?), so i created a dummy panel to 
pass to it. The first panel had a tiny size, and when i later presented the 
graphics to another window, which was larger, it was abvious that the 
rendering had been done in low resolution and it was not stretched to fit 
the larger window. That is what you ment, I guess.

Why can i not pass null to the createDevice? 

You should be able to pass a null HWND for CreateDevice, but then, you're 
forced to pass the HWND each time at present.
You can get rid of the stretching by adjust your viewport dimensions prior 
to rendering to that window.

Wessam Bahnassi
Microsoft DirectX MVP,
Lead Programmer
In|Framez