Hybrid Back/Forward path tracing (aka BiDir without MIS)

Discussion related to the LuxCore functionality, implementations and API.
User avatar
lacilaci
Donor
Donor
Posts: 1969
Joined: Fri May 04, 2018 5:16 am

Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by lacilaci »

epilectrolytics wrote: Sun Jul 07, 2019 8:09 am I tested several engines with path depth = 8 and 100 samples:
EnginesTest.jpg
LightCPU performs far better in terms of noise and speed than all other engines, even BiDir, for caustics, direct and indirect light!
It only lacks display of specular bodies and lights which it cannot do by design.
I'd like to see an option for full light tracing in the new hybrid engine where the path tracer only provides those missing parts.
Like PGI light tracing seems to be a gold mine ready to improve all kinds of things with :D

Disturbing finds:
BiDir looks different (strange dark corners) than Hybrid, that should not be the case given both are unbiased.
PathMetro is not able to get reflective caustics which I think it should do.
interesting finds.

looks like something is wrong with pathocl direct light sampling
epilectrolytics
Donor
Donor
Posts: 790
Joined: Thu Oct 04, 2018 6:06 am

Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by epilectrolytics »

B.Y.O.B. wrote: Sun Jul 07, 2019 8:27 am But is LightCPU faster than PathOCL? I doubt it.
I can't believe it myself but apparently it is.
Screenshot after 60 seconds, LightCPU with 200 samples vs Hybrid PathOCL with 1800 samples on RTX 2070 + GTX 1060!
Only PGI would be faster but light tracing is unbiased (and easy to set up).
Screenshot.jpg
The problem is as Laci has mentioned elsewhere, PathOCL struggles with shadow converging.

LightCPU is the ultimate beast destroying them all :o :shock: :mrgreen:
User avatar
B.Y.O.B.
Developer
Developer
Posts: 4146
Joined: Mon Dec 04, 2017 10:08 pm
Location: Germany
Contact:

Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by B.Y.O.B. »

I would be careful with conclusions after only testing one scene.
Try some more complex scenes from our example scene repository.

By the way, what's your CPU?
epilectrolytics
Donor
Donor
Posts: 790
Joined: Thu Oct 04, 2018 6:06 am

Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by epilectrolytics »

See my signature, it's a Ryzen 2700X.

You are probably right that this advantage will not hold for complex scenes.
I just tested the Classroom and Benchmark scenes and they don't look well.
But because light tracing cannot connect to the camera from specular surfaces it does not work with glossy materials as well, so that would be one reason.
It needs to be combined with path tracing to account for that.
(Edit: Path tracing only for first hit = glossy or specular because light traces everything else till last hit = diffuse or scattering.)

Still I think it should be tested if full light tracing can make the Hybrid engine even better than it already is!
Last edited by epilectrolytics on Sun Jul 07, 2019 12:28 pm, edited 1 time in total.
bnzs1
Posts: 7
Joined: Sun Jan 20, 2019 9:31 pm

Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by bnzs1 »

is there are plans to expose setting of Hybrid Back/Forward path tracing in blender for 2.2 version ot it done for 2.3 version?
User avatar
B.Y.O.B.
Developer
Developer
Posts: 4146
Joined: Mon Dec 04, 2017 10:08 pm
Location: Germany
Contact:

Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by B.Y.O.B. »

bnzs1 wrote: Sun Jul 07, 2019 9:50 am is there are plans to expose setting of Hybrid Back/Forward path tracing in blender for 2.2 version ot it done for 2.3 version?
It is already exposed, but you need the 2_79_maintenance branch:
https://github.com/LuxCoreRender/BlendL ... aintenance
bnzs1
Posts: 7
Joined: Sun Jan 20, 2019 9:31 pm

Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by bnzs1 »

Dade wrote: Thu Jun 27, 2019 12:38 pm I'm going to use this as manifesto:

Image
(aka "if you use something else, you are out of your mind" :lol: )
hi. can you share this scene with setting in blender for left part of screen? i can't understand how to use this Hybrid Back/Forward path tracing.....
epilectrolytics
Donor
Donor
Posts: 790
Joined: Thu Oct 04, 2018 6:06 am

Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by epilectrolytics »

bnzs1 wrote: Mon Jul 08, 2019 3:34 pm hi. can you share this scene with setting in blender for left part of screen? i can't understand how to use this Hybrid Back/Forward path tracing.....
Hi,
here is the blend file:
cube3a.blend.zip
(248.81 KiB) Downloaded 154 times
Have you installed the recent blender add-on from the 2.79 maintenance branch on GitHub?
Then you can activate light tracing as indicated in this screenshot:
Screenshot.jpg
PetrT
Posts: 81
Joined: Sun Dec 02, 2018 6:13 pm
Location: Russia
Contact:

Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by PetrT »

have 2.79b and 2.2 beta 2
updates makes nothing
this option does not appear
User avatar
B.Y.O.B.
Developer
Developer
Posts: 4146
Joined: Mon Dec 04, 2017 10:08 pm
Location: Germany
Contact:

Re: Hybrid Back/Forward path tracing (aka BiDir without MIS)

Post by B.Y.O.B. »

You need this branch: https://github.com/LuxCoreRender/BlendL ... aintenance
(Click the green "clone or download" button, download zip, then place LuxCore binaries in the "bin" folder like described here).
If you don't get it to work you will have to wait for the next release.
Post Reply