Smarter IPR, less often restarting - e.g. should not be restarted only from saving file (and other minor actions) - could be user defined

[BeneZ]

During IPR waiting it would be great to be able to save the file without triggering a restart of IPR.
In general the IPR restarts too often, which is doing unneccessarily the opposite of what it is actually intended for: time-saving.

Maybe there could be a IPR mode inbetween, which only restarts when a "refresh" button is pressed
and / or
where it can be defined, which kind of actions trigger restart and which not.

Sometimes I use the IPR to examine elements (while the IPR-camera is not moved), but despite I do not change anything at the scene, the IPR is restarting.
Or another example: When I enable or disable a region render while it is already progressed in IPR, then it should not restart everything from scratch, it should just render that region further without having to clear everything.
Or when I only set a key on the camera, that changes nothing at all...
At the moment the user is nearly forced to do nothing, if he does not want to loose the render progress.

[M.Max]

+1 from me too.
Other renderers have "lock" button to prevent IPR from refreshing, that way you can continue working on something else (modeling for example) while it's rendering.
That region issue is only with CPU so I think it is "easy" to fix.

[fixeighted]

Agreed, it can end up being a time-waster rather than a workflow enhancer. I love it but there is def room for tweaks.
Maybe there could indeed be a lock button - or maybe there could be a way to re-use the initial light cache for all subsequent changes until a refresh is called, so the only thing it's doing is refining the image noise
This would enable us to tweak things that would not greatly influence the overall lighting, like materials, for example.
Even regarding camera movement, cannot the initial light cache consider the overall scene? Like the flythrough setting that used to be used. Maybe that's not how it works but it would be cool.

[dgruwier]

I have the opposite problem. For example, tweaking extra texture elements seem to not restart the IPR even though things have changed that are essential to the image.

I'd suggest having both a "refresh" and a "lock" button added to the VFB, so we have full control in case we don't agree with the IPR.

[fixeighted]

Like what? It's useful to know.
I know displacement is quirky and I always forget about that - seems it works sometimes and doesn't others, or something; I've not tested it thoroughly but it seems to catch me out a fair bit.