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Some Puzzled Questions about D3D!!!

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In windowed D3D application, 1.Can the resource(e.g, a vertex buffer)that is created by one D3D device be used by another D3D device in the same application? Within the SDK document, I''ve not found the an exact answer. 2. Can a window be bounded to multi D3D devices(that is to create multi devices using the same window)? May this feature is much like multi swap-chains within one device and sure not good to do that. But is it possible? I''ve not tested these problems. But I think the first should be yes or there will be some limitation for application development. But I amn''t sure the second(I think it should be) because I do''t know much about the specification of D3D and the adapter.

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AFAIK.

No & No!...

1. A surface in video memory on a device is local to that device - a surface on another device is local to that device. The only way data can be transferred between 2 devices is via system memory which is slooow. The only exception to this is cards which expose two device (e.g. nVidia TwinView or Matrox DualHead).

2. If you have multiple D3D devices active you have multiple adaptors active. There is no way for 2 adapters to output to the same monitor. Each active adapter is bound to a unique monitor.


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Simon O''''Connor
Creative Asylum Ltd
www.creative-asylum.com

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I should probably add some points of clarification about what goes on in Windows:

1. When a window appears on two monitors at the same time (for example it''s in the centre of the desktop), any DirectDraw or Direct3D rendering takes place only on *one* of the devices. The surface data is then copied with the CPU (Lock, Copy, Unlock) across to the other device manually, pixel by pixel.
You can see this in practice, try running one of the D3D samples (such as the mesh optimise one), see the difference in frame rate when the window is stretched across 2 monitors instead of just one.

2. In multimonitor apps, there are two types of window. The first is the FOCUS window and the second is the DEVICE window. Your application should have only *one* focus window which is shared between all devices. The application should have a unique device window for each device. The device window for *one* of the devices can be the same window as the focus window.

--
Simon O''''Connor
Creative Asylum Ltd
www.creative-asylum.com

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