Does Avid Symphony internal effects render fractional interpolated values for example when keyframing small positioning changes?

If not, how about Boris?

Unfortunately, no it doesn't.

Slight movements should have sub-pixel interpolation rendering. 

Without it, movement is choppy i.e. position snaps to nearest pixel.

editdudes:

 

Does Avid Symphony internal effects render fractional interpolated values for example when keyframing small positioning changes?

 

If not, how about Boris?

AFAIK, this is what the HQ button is for (hence, non-realtime). You can certainly see the difference with subtle, slow xy moves in effects like 3D Warp. Also, try the console: 'setresizetype 9' for polyphase filtering.

Regards,

How do you change to Bi-Linear?  Is it a console command or is this invoked with the HQ button?

It used to be a consle command only but since version 3.1.1 it is in the Standard setting under Render Settings image interpolation. HQ is used if effect is promoted to 3D and becomes a software based render, no hardware assisted render. Not every effect can use HQ render, which changes to the Polyphase interpolation, but a reposition effect should improve as well as using 16bit depth.