Chris_J_H

Thanks - that's helpful.

It doesn't appear that there is any way to clear portions of a DSV.  However, I would recommend just clearing the whole DSV at once, and then repopulating the content.  Do you have the same update rates with each of the sub-views?

I hear you on clearing the whole DepthStencilBuffer and then repopulating (works for the 2 non-overlapping main views)... however, not for the overlapping sub-views.The sub-views are currently updating at the same rate... If they weren't I guess I would have to render them to a texture and render that texture to the screen each frame - right? In fact I may move to something like that in due course as I may need a mini-HUD/frame around the subviews and it does seem a waste to render them as frequently as the main view...  Anyway - interested to hear general approaches to this that would be used... Thanks.

Thanks MrHeisenberg - I did not know you could use the Windows 8 SDK on Windows 7. Not sure I want to install it though - maybe I'll write my own functions to avoid having to do that.

MrHeisenberg - thanks for your observations. I ran your code on my pc (replacing your test matrix with the identity matrix as it was giving error values in my output, 5mm iterations). I see a 12% speed gain for the optimized functions on x64 and 27% gain on x86 compilations. Given I really only care about x64 at this point, I agree, it doesn't seem a big deal... Then I tested: 1) add inline to the optimized functions and 2) declaring them as _fastcall (which the docs recommend) - neither seem to make any difference within the noise of the data for either x86 or x64. I Then refactored the code to eliminate the calls completely for the optimized calculation: to get a total 21% gain in x64 and 33% total gain in x86 which starts to be more significant. I checked my compiler (VC++) setting for inlining functions: it is at the max (/Ob2): if I change the inline declaration to _forceinline (!) I finally get the same effect using functions as if I had refactored the code... hmm maybe some other settings on the compiler are interfering...