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Weird clipping with viewport.

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Hi, In my app on my home machine with a Radeon 9800 Pro in it, there's no issue. However, on my machine here at work, with a rather craptastic SiS chipset I'm getting a strange issue. My viewport seems to 'clip', that is it only shows a little more than 1/4 of the scene. This doesn't happen right away, only after I move the window. The scene is not 'squashed' as you would expect from a viewport resize down to 1/4 of the screen, just clipped. I've tested the view port settings (wrote them once per frame to my log file, no change). I've tried intercepting the paint event for the control it's using as the render window, nothing. The only thing that I have done that actually works is reset the viewport every frame, this clears up the issue just fine. I've used the reference device with D3D and there doesn't seem to be any problem there, so it's possible it could be a driver thing. So now my questions are as follows: Does this sound like an issue with the driver? How horrible is it to set the viewport for each frame?

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In the interest of making info available for all to use, I posted the same question to the DirectX mailing list and got the following answers:

1. This is most likely a driver bug.
2. "Tom Forsyth to DIRECTXDEV
Calling SetViewport is extremely cheap. Calling it once a frame should be


The second part should be of interest to at least one or two people who are psychotic about optimization.

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