I wrote 2 weeks ago about problem with motion blur in my engine. When camera moves using keyboard, motion blur is smooth. But when I rotate camera using mouse motion blur is stepping (not sure if I used proper term). Now I rethink my problem and it brings me new questions.
To rotate camera I use mouse delta which is difference between last position and current position. But it is expressed in pixels. Furthermore WinAPI events doesn't have per-pixel precision.
I saw that engines uses it's own screen coordinates which is float-based (http://www.esenthel.com/wiki/index.php?title=Screen_Coordinates). I checked that and I see that even small movement (smaller than 1 pixel) is detected. I believe that this is the solution to my motion blur problem and also with another further problems (for example different size of GUI components on different resolutions).
And here is my question. How can I get such mouse precision? I read about WM_INPUT and dividing delta by mouse DPI, but there are two problems - we can't get mouse DPI using WinAPI and mouse event still return value in pixels.
Where can I find some informations or example of solving this problem?