CGI tech news box

General project and community related discussions and offtopic threads.
kintuX
Posts: 377
Joined: Wed Jan 10, 2018 2:37 am

Re: CGI tech news box

Post by kintuX » Thu Jun 20, 2019 5:02 pm

"Bump Terminator" :twisted:
preview.jpg
We present a technique to hide the abrupt shadow terminator line when strong bump or normalmaps are used to emulate micro-geometry. Our approach, based on microfacet shadowingfunctions, is simple and inexpensive. Instead of rendering detailed and expensive height-fieldshadows we apply a statistical solution built on the assumption that normals follow a nearlynormal random distribution. We also contribute a useful approximate variance measure forGGX, which is otherwise undefined analytically.
source: A Microfacet-Based Shadowing Function to Solvethe Bump Terminator Problem

and much more... SIGGRAPH 2019 Ray-Tracing Roundup

User avatar
lacilaci
Donor
Donor
Posts: 1146
Joined: Fri May 04, 2018 5:16 am

Re: CGI tech news box

Post by lacilaci » Thu Jun 20, 2019 5:32 pm

I'm gonna sacrifice a goat and maybe a dog to have the gods of shaders create a treatment for this shadow terminator. Really, whenever I change lighting I inspect my renders and pray that this f*ing issue won't come up.

patrickawalz
Supporting Users
Posts: 33
Joined: Tue Dec 05, 2017 1:45 pm

Re: CGI tech news box

Post by patrickawalz » Sat Jun 22, 2019 4:23 pm

This seems really easy to implement. They provide a listing of their code and describe how to add it into their renderer(using it as a lighting term multiplier). Im sure the dev's will get to this soon to at least give it a go.

They do mention that this breaks reciprocity of light tho so this may be better to enable as an optional fix

User avatar
B.Y.O.B.
Developer
Developer
Posts: 2752
Joined: Mon Dec 04, 2017 10:08 pm
Location: Germany
Contact:

Re: CGI tech news box

Post by B.Y.O.B. » Sat Jun 22, 2019 4:43 pm

patrickawalz wrote:
Sat Jun 22, 2019 4:23 pm
They do mention that this breaks reciprocity of light tho so this may be better to enable as an optional fix
Does this mean it breaks the "bidirectional" nature of a BxDF?

Also, does this only apply to bump mapped surfaces or does it also work on any other surface? Because we have a general problem with the terminator, not only when bump mapping is used.
Support LuxCoreRender project with salts and bounties

patrickawalz
Supporting Users
Posts: 33
Joined: Tue Dec 05, 2017 1:45 pm

Re: CGI tech news box

Post by patrickawalz » Sun Jun 23, 2019 12:55 am

B.Y.O.B. wrote:
Sat Jun 22, 2019 4:43 pm
patrickawalz wrote:
Sat Jun 22, 2019 4:23 pm
They do mention that this breaks reciprocity of light tho so this may be better to enable as an optional fix
Does this mean it breaks the "bidirectional" nature of a BxDF?

Also, does this only apply to bump mapped surfaces or does it also work on any other surface? Because we have a general problem with the terminator, not only when bump mapping is used.
Yes they found that applying this as a scaling factor to both the light and bsdf produced darker edges than they would like so they are only applying it to lights.

And yes this fix seems only for the terminator when a bump map is involved.

There is a new article I'll have to look up that is being presented at siggraph called "taming the shadow terminator" that might be a good solution to the general case but it isn't even in preprint yet

User avatar
B.Y.O.B.
Developer
Developer
Posts: 2752
Joined: Mon Dec 04, 2017 10:08 pm
Location: Germany
Contact:

Re: CGI tech news box

Post by B.Y.O.B. » Sun Jun 23, 2019 7:14 am

Thanks for the insight.
What do you think about this earlier post on the topic? viewtopic.php?f=9&t=119&p=1969#p1969
Support LuxCoreRender project with salts and bounties

User avatar
lacilaci
Donor
Donor
Posts: 1146
Joined: Fri May 04, 2018 5:16 am

Re: CGI tech news box

Post by lacilaci » Sun Jun 23, 2019 7:57 am

patrickawalz wrote:
Sun Jun 23, 2019 12:55 am
There is a new article I'll have to look up that is being presented at siggraph called "taming the shadow terminator"
I've only seen the comparison picture from that and it's already mind blowing :shock:

patrickawalz
Supporting Users
Posts: 33
Joined: Tue Dec 05, 2017 1:45 pm

Re: CGI tech news box

Post by patrickawalz » Sun Jun 23, 2019 2:25 pm

B.Y.O.B. wrote:
Sun Jun 23, 2019 7:14 am
Thanks for the insight.
What do you think about this earlier post on the topic? viewtopic.php?f=9&t=119&p=1969#p1969
It sounds like they are doing some version of dynamic epsilon along the same lines as to what we have already been doing since machineepsilon was introduced in the original lux years ago, albeit with some form of interpolation. But theas was more a feature description rather than a technical report, with no explanation of how they really achieved it. My money is on the upcoming 'taming the shadow terminator' talk as hopefully it will give some of the details on how it was done. It's a talk tho, so it might just be some PowerPoint slides in the end without any context, but at least one of its authors ( yining karl li) is an active blogger so it might be possible to contact him and get insights after the talk is presented.

User avatar
B.Y.O.B.
Developer
Developer
Posts: 2752
Joined: Mon Dec 04, 2017 10:08 pm
Location: Germany
Contact:

Re: CGI tech news box

Post by B.Y.O.B. » Sun Jun 23, 2019 2:50 pm

Alright, looking forward to the presentation then.
Support LuxCoreRender project with salts and bounties

User avatar
Dade
Developer
Developer
Posts: 2604
Joined: Mon Dec 04, 2017 8:36 pm

Re: CGI tech news box

Post by Dade » Thu Jun 27, 2019 12:47 pm

Interesting: "Optimal Multiple Importance Sampling" (https://graphics.cg.uni-saarland.de/pub ... l-mis.html)
Support LuxCoreRender project with salts and bounties

Post Reply