Point Bassed Occlusion for GI

[CHRiTTeR]

Check this page for the pixar papers.
http://graphics.pixar.com/library/
Its a good page to bookmark ;)


About the flicker free GI in arnold. Check out cloudy with a chance of meatballs. Im pretty sure sony rendered it using arnold.

[kage-maru]

http://graphics.pixar.com/library/PointBasedColorBleeding/paper.pdf

[Whirlwind123]

actually had it bookmarked forgot to look in all my google searches hehe

I know about cloudy, just wondering if there was any written info about it :)

Thanks for the PDF link!! that's what I was looking for :D


Edit: for example is arnolds GI point based?

[wurp]

more Arnold questions :)

I'm one of the betatesters of Arnold so I can answer a few questions.

Arnold is a raytracer and so its GI is done that way, using a brute force approach, so there is no prepass for GI like with vray or mr for example, it simply starts rendering straight away.
Since its a brute force approach it doesn't really flicker like MRs gi can do, instead you can get some noise if the sampling isn't set high enough. The GI is accurately computed per pixel so there isn't any need to use occlusion or the likes to enhance any detail.
Another nice thing about arnold is that motionblur and dof can be used even together and still rendertimes doesn't skyrocket like with mr.


Sony Imageworks has pretty much switched to rendering all their films in Arnold, both monster house and the new cloudy with a chance of meatballs is rendered fully in arnold with GI in every shot. As far as I know monster house didn't have any motionblur, but cloudy was rendered with real 3d motionblur so even that's now fast enough to raytrace even for film.

[Whirlwind123]

Thanks for the info! :D

Really looking forward to giving arnold a try. I almost never use brute for gi (vray) since it usually proves too slow comparared to the interpolated methods.

Would love a head to head between arnolds fast bruteforce gi and rendermans point based gi.

[ndeboar]

Would love a head to head between arnolds fast bruteforce gi and rendermans point based gi.

Obviously you havn't read the other comparison threads, be prepared for a lot of flamming.

I do like the sound or Arnold, being a Prman user, it can be really time consuming setting up depth maps and pre-passes.

[rendermaniac]

So is Arnold actually going to be released as a commercial product?

[Whirlwind123]

I believe so :)

[julienTD]

Yes arnold is going to be released in xsi as a plugin. maybe in 2010. arnold is impressive and fast but need a renderfarm for a project like cloudy with tone of object and displacement but I agree it's the fastest and most beautifull raytracer I ever seen.

Renderman point based is really handy in production and especially in big scenes with complexe object including fur and displacement. it's really fast to compute and free flicking. the only drawback is the need of a prebaked pass but you can setup your pipeline to compute only one time this pass and reuse it all the time.
We have all our pipeline based on point cloud and point based and it's really efficient. the big advantage is also in the memory footprint, using point cloud you can render very complex scene on a 4gb ram system only. this is not possible with a raytracer even with arnold. And last but not least point based is really easy to customize for your needs.

[wurp]

Irradiance caching can always be made faster than brute force GI, however in arnold they really spent a lot of time making it fast. The fact that I don't need to wait for a prepass makes it worth it alone for me. Also the gi in arnold doesn't add to the memory usage at all.

As for comparing pointbased GI with arnolds, I've only ever tried 3delights pointbased gi so I can't speak about prmans..
At least in 3delight the pointbased GI is not as accurate in terms of light bounces, forget lighting an interior purely with area/portal lights and pointbased gi for example. What's nice about pointbased gi though is that its completely noisefree and renders pretty fast too, which can be a big plus..




Thanks for the info! :D

Really looking forward to giving arnold a try. I almost never use brute for gi (vray) since it usually proves too slow comparared to the interpolated methods.

Would love a head to head between arnolds fast bruteforce gi and rendermans point based gi.

[Whirlwind123]

Its great to get quick info from people who know what they are talking about :)

So looking ahaid in the future for the purposes of production (and I know I am oversimplifying alot here) would it be?:

---Massive scenes
---Lots of displacement
---Fur
---Looking for Elegant but not entirly accurate GI soliution
---Person preference for REYES

Then a Renderman complient renderer is you best bet


--- Lots of shiny things
--- lots of refractive things
--- Easier to approach something closer to a photo reel solution (?)
--- Personal preferance for a raytracer

Arnold would be kind

Both give very very cheap motion blur and DOF and SSS (assuming for Arnold on the last two). Both offer flicker free GI solutions not too expesive.

To be clear please read all of this in the form of a question not me giving authorative information.

Also sorry for all the questions :P

[Whirlwind123]

At least in 3delight the pointbased GI is not as accurate in terms of light bounces, forget lighting an interior purely with area/portal lights and pointbased gi for example.

Interesting ... could you elaborate a bit more.

I realise that at this point it would probably be benifical to try for myself but its quicker for me to bug you at this moment in time :D ... lots of experimentation time has been penciled in for 3Delight.

[playmesumch00ns]

The point based techniques are only an approximation. They're good for surface to surface bouncing but do not compute visibility properly so you don't get very good shadows from it.

[wurp]

In all raytracers I have tried if you light an interior you can pretty much just place portal/area lights in all the windows with exponential falloff, and add a sunlight and enabled gi, and it gives you a nice result, try this in 3delight and you will be very disapointed, if you look at the new paper from pixar regarding pointbased GI in UP you will see that when they show the with/without GI comparison the images they are actually rather similar, the GI just makes it a bit "nicer" and warm and it looks like they already did most of the lighting work using traditional lighting, I could be off here though.

like playmesumch00ns said, it's just an approximation and at least in 3delights current version you don't get much gi shadows" at all.

Interesting ... could you elaborate a bit more.

I realise that at this point it would probably be benifical to try for myself but its quicker for me to bug you at this moment in time :D ... lots of experimentation time has been penciled in for 3Delight.

[Whirlwind123]

Do you have a link to the paper of pointbased GI in UP wurp? Cant find it on the pixar library.

So when using a raytracer interiors are easy to light and nice shadows arent are problem (my area of experitse) but using GI with 3Delight in an interior requires more work.

So what is the more work people do to achive the shadow detail? more lights? are you still placing bounce lights as if you were simulating the GI even when its on, or shadow only lights or working with ambient occlusion aswell?

[wurp]

have a look here:
http://graphics.pixar.com/library/PointBasedColorBleeding/SlidesFromAnnecy09.pdf

[Whirlwind123]

*ahem* ooops :blush: when I came across the link to a pdf there myself I just assumed it was this pdf

http://graphics.pixar.com/library/PointBasedColorBleeding/paper.pdf

sorry lol

I feel I am getting the idea now -- light a scene as you would without using GI with the usual production lighting techniques and then see what sort of difference, artistically, adding point based colour bleeding would have and adjust the scene acordingly. (I guess removing some manual bounce lights where they are no longer needed). Its just a nice bit of extra lighting detail at the end keeping everything as artisticly controlable as it was without without it.

I guess the arnold workflow is more akin to what I am used to working with V-Ray.

Basing the decision on what engine to use on the asumptions I made earlier.

I appriciate all the info guys!

[julienTD]

Yes of course arnold and a raytracer are lot more accurate than point based approximation, but they are getting better and better precision from now with point based, the result is almost the same as the raytraced one in RPS 15. I don't know much about the next 3delight because I only tested the last release.
The only thing I noticed in arnold was the need of a big sample to get smooth and clean of noise image, but that's the same technic of brute force path tracing renderer.
for interior you can use object lighting to mimic portal or multiple bounce, you can even do photon emmiting from point cloud with Prman. So it's kind of tricky compared to arnold but renderman is a standard for customisation and shader now, that's the big advantage, arnold is not well known exept in few company.I think at sony they used both arnold and Prman on G-force arnold for the background and Prman for the character and fur.Both can do really good job, but arnold seems less painfull for sure.

the big advantage of point cloud is they are cached on the disk so you can reuse them in a relighting like in the new Prman relighting engine, this can save lot of time in a production.

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