Add 'IPR'

[bentoogood]

A majority of production renderers offer some form of raytrace hider based interactive rendering (often know by the maya name 'IPR').

This approach to setting up lighting and shading is gaining traction in production.

What features would we expect?

• interactive transformation of lights
• interactive hiding/showing/creating/deleting of lights
• interactive transformation of cameras (whilst viewing scene through camera)
• interactive transformation of objects?
• interactive changing current frame?
• tweaking of shader (surface, light) parameters (all types?)

What changes would reasonably require a re-export of the scene?

[bentoogood]

first steps
#140
#141

[andrewkaufman]

@johnhaddon could you update this with the current state of features and what is missing? Please Include things that need performance improvements, and things that need features from 3delight.

[johnhaddon]

I've updated the original text, turning it into a todo list, noting what is done, and adding one more. I don't think "interactive changing current frame" should be an item - that basically requires "interactive changing everything, including object deformation", which I don't think is very likely at this point. I'll remove that if that's OK with you.

Short of attempting hierarchy hashes at this point, optimisation is going to be a case of general optimisations in the existing Gaffer engine - big ones should be covered by #427 and #760, and others won't become apparent before we actually do the work and profile it.

As far as I know, we don't need anything from 3delight, except maybe for object movement. We do have issues 0004687 0004628 open still - which I think may have been addressed to some degree but not as much as we'd like. We might also like to ask for a path tracing IPR approach to get noisier result quicker - more of a question for Daniel though. I'm sure things will come up as we rely more heavily on this stuff though, so we'll have to just ticket as we go...

[bentoogood]

I don't think "interactive changing current frame" should be an item - that basically requires "interactive changing everything, including object deformation", which I don't think is very likely at this point. I'll remove that if that's OK with you

hows about leaving it on as a wishful 'one-day' dream?
imagine being able to inspect your animated robot cars in real time!
https://www.youtube.com/watch?v=hbW_l5oY9X8

[johnhaddon]

That link was very fancy! I'm definitely all for interactive everything. As far as Gaffer and IPR is concerned, changing frame is basically irrelevant - changing frame might change nothing at all, or it might change everything - and the same goes for tweaking a single value on a node (a SceneSwitch for example). So maybe we should instead add on "object deformation" and "addition/removal of objects" as the dream items?

[pberto]

I'd also say you need to add in that list support for live edits of the environment texture which is important for interactive IBL (currently this is possible but requires a tdlmake and in the ideal world of quick-n-dirty™ results the tdlmake should be bypassed).

[johnhaddon]

Closing this, since our Arnold IPR implementation is basically feature complete, and the missing features for RenderMan are limitations of the renderer rather than of Gaffer now.