Gang,
Nothing earth-shattering here, but I did a bit of playing around with PBR in H9.5 I created a very simple scene using a mapped dome, a mapped ground plane, and a motorcycle. I assigned built in shaders from the material palette to different parts of the motorcycle and added a single area light above the motorcycle. Very basic and quick and dirty…

I ran 3 sets of tests, a vanilla raytraced Mantra test (nonPBR) to use for comparison. Then a lo-quality PBR render with very few samples, and then a hi-quality PBR render with loads more samples:

Observations:
- The PbrLo renders were lighting fast, and even though grainy as hell, it was very indicative of the results we would get with the higher quality renders – so it is very feasible to do lo-quality iterations during the day and then run hi-quality overnight with few surprises (tsk, tsk).
- I was pretty pleased with the amount of richness I got out of the PBR renders with the bounce illum from the ground onto the motorcycle as well as the color bleed from the motorcycle onto the ground
- The render times for the PbrHi renders were around 1.5-3hrs a frame, but I have admit I was expecting worse render times. Memory usage was not prohibitive – so I need to investigate perhaps leveraging more from RAM/caching to reduce render times…
- I had a nice hack ready to place geometry around my area light for reflections, but area lights illuminate/reflect realistically which is such a nice bonus…

I'll continue running a few more tests and reporting back if anyone is interested… Also keen to bring H9.7 into the mix since that has some pbr optimizations…

more to come!

the third one looks very nice man, great tests.

hey
nice to see ppl playing with PBR!
i've been messing with it quite a bit lately to, i'm really keen on using it more in production.(we've pretty much switched our rendering pipeline to mantra)
i think the next release or two is going to be great and hopefully a big step in using it for work!!

things i would love to see in Houdini in general:
photometric lights
non square area lights
skylight portals
physical camera http://www.spot3d.com/vray/help/150SP1/vrayphysicalcamera_params.htm [spot3d.com]
tone-mapping
better gamma correction support

yes i know these are very Vray/mental ray user type features, but hey these are actually useful features me thinks.

hopefully I'm not hijacking your thread to much

jason

They already have non-square area lights….

heydabop
They already have non-square area lights….

He means rectangular, I believe

Hey, nice! From the grain in the second image it appears that you're using micropoly PBR, any reasons for that?

cheers,
Abdelkareem

Hey, nice! From the grain in the second image it appears that you're using micropoly PBR, any reasons for that?

Yes you're totally right, I used micropoly PBR, but there really was no real reason for that. It's hard to see from the stills, but all my tests were motionblurred and I was under the impression the mblur would be less grainy under micropoly pbr. But I have yet to confirm that through more tests…

Are you consistently using PBR over micropoly PBR Abdelkareem?

jason_iversen

heydabop
They already have non-square area lights….

He means rectangular, I believe

yeah, this is correct, sorry i guess i should be more specific

jason

gyepes
Yes you're totally right, I used micropoly PBR, but there really was no real reason for that. It's hard to see from the stills, but all my tests were motionblurred and I was under the impression the mblur would be less grainy under micropoly pbr. But I have yet to confirm that through more tests…

Are you consistently using PBR over micropoly PBR Abdelkareem?

No, not consistently, really depends much on the situation. If you are dealing with mostly specular reflections and motion blur it might be better to use MPBR. The main advantage of MPBR is being able to separate pixel samples from shading samples (smearing shading samples over an area etc.), and being able to prioritize objects or shaders via the shading rate, so it's a great help when you're dealing with motion blur and/or DOF - Mantra 9.5 doesn't support this separation in pure raytraced PBR.. MPBR also needs way less memory than PBR.

The disadvantages of MPBR are its relative lack of speed (the same scene you rendered will probably need alot less time in PBR) and the same issue that haunts raytracing in the micropolygon engine, which is jagged reflections due to dicing rasters. Upping the shading rate will help against this.

Plus, the PBR undersampling grain looks much nicer (almost like film grain), and is way easier to get rid of in comp if you're in a hurry

Cheers,
Abdelkareem

That makes a ton of sense, thanks so much for the tips! I'll definitely have a play with straight up PBR…