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Discussion
Light can be in USD in Univty Unity but we can't move them in Unity.
How engine centric lights are? It seems they are very engine centric.
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At Remedy, light are from now, engine lights only, because of the probes that are used. But basic properties should be transferrable into USDLux.
Infinity Wars Ward : Some maths are needed between Omniverse and DCC. They are not believing that USDLux have the full description of lights for the engines : it is a one way trip with caculus calculations for units.
Light are used for cinematics, etc. eg : headlight will work differently in realtime that in cinematics.
Emissive materiax materials are not listed as lights. They are not supported in UsdShade. Basically USD is not supporting emissive for now.
There is no light asset for now in the USD assets. There should be added.
Question : how to make it good to have the correct result? WHich Which render to use to have the source of truth?
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Sebastian "spiff" Grassia mentionned mentioned there is kickstart to incorporate PhysLight. There is still a lot to do. https://github.com/wetadigital/physlight
Thoms Chollet is wondering if it would be possible to have schemas for lights.
Koen mentionned that USD Lux and USD PreviewSurface are the less least common denominator.
Sebastian "spiff" Grassia (Pixar) : The idea for USDLux is to be the base line for lights. AHd And then having schemas for lights that will support actual lights (eg the Renderman plugin)
Having a DCC set of specifications makes sense
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Jeremy Cowles explained that his previous experiences with FBX and GLTF made him thing think that having a staring starting point ( position, orientation, type) is way better than nothing.
Sebastian "spiff" Grassia : alot a lot of work to support light is done in Renderman. They (Pixar) need people to come back to them with concerns.
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Jeremy Cowles we could make the game engine the hydra delegate. At Unity they made experiment but they stopped.
Levi Biasco mentionned mentioned it could be a lot of work
Koen explained that if your game engineis engine is an hydra delegate you can switch from Renderman to your gameenginegame engine!
Jeremy Cowles suggested also that it would be the last part of the USD integration.
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Koen : but it is too much effort.
There is no software that can handle large levels because of the amount of optimisation specialization and optimization we have in game engines to make it possible.
USD to create hierarchy
Michael B Johnson is wondering is OpenUSD could be a way to create hierarchy.
Koen replied that in games it is more twhat what the camera is seeing.
At remedyRemedy, USD helps creating level and the asset are created in Maya.
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Ubisoft is preparing a PR for LODs (could someone link the proposal here?)
Is there an ETA for expressin expression driven attribute?
Sebastian "spiff" Grassia : more than one year out
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Koen is wondering how to use join joints in UsdSkel ? How to create constraint ishconstraints? How to attach bones?
How to use rig at runtime? : eg how to attach a gun to an hand?
Sebastian "spiff" Grassia mentionned mentioned that is TBD : it is not explicity explicitly designed yet. How much is part of USDSkel and how much is part of rigging?
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