LuxCoreRender v2.0alpha5 released

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kintuX
Posts: 170
Joined: Wed Jan 10, 2018 2:37 am

Re: LuxCoreRender v2.0alpha5 released

Post by kintuX » Sat Feb 24, 2018 2:47 am

B.Y.O.B. wrote:
Fri Feb 23, 2018 7:27 pm
Yes, I remember an article about the feature in Thea but I can't find it anymore.
The only thing they offer is an example image, scroll to the bottom of this page: https://www.thearender.com/site/index.p ... iased.html
However I don't know if their workaround/hack is truly unbiased (but if it works, I'm not complaining about a little bias).
More on the subject:

Terminator Artifact Treatment (@ Thea Render Forums),
based on "It's Really Not a Rendering Bug, You See…"
from "Mistakes to Make on a Raytracer" (@ geekshavefeelings.com)
Terminator Artifact Treatment

by giannis » Sun Dec 12, 2010 10:16 pm
In the next revision to come, there is an important fix, for a problem known as the "terminator artifact". For your information, this artifact is seen at the limit of lighting models that have low-poly subdivision (it is more obvious in low-poly meshes - it actually can be seen on arbitrarily detailed meshes on close up). It is very nicely described in this paper where it is identified as an inherent render artifact rather than a bug! This is why, you probably have seen this in a lot of other renderers as well.

As far as we know, the majority of unbiased renderers suffers from this problem. In biased renderers, it is somewhat easier to fix the problem. A nice (biased) solution used, is to appropriately tweak the material reflectance, compressing it and "pushing out" the jaggy artifacts. If an inherent solution does not exist on the renderer, the typical workaround is to subdivide models to a finer degree (something that costs both memory and speed).

In Thea Render, we didn't want a solution that could alter/bias material appearance but instead we very carefully compensate for the energy loss due to the terminator artifact dark zones. Our solution produces smooth renders even for very low-poly models with only the basic assumption that the subdivision is uniform (i.e. not abruptly changing). We are actually very happy that we have this working out-of-the-box for all engines. As an example, you can see in the images below some spheres rendered with sun light in current and next (forthcoming) revision (note that the spheres have increasing subdivision detail from left to right).

Current revision showing terminator shading artifacts.
Image

New (forthcoming) revision produces perfect/smooth shading, artifact-free.
Image


With this enhancement, Thea moves ahead and we believe as an established world class renderer, quality-wise. We are proud of making Thea better and we hope that you are proud of being a Thea user and getting artifact-free renders - getting ahead of unbiased competition. ;)
IIRC, Corona dev. mentioned setting epsilon value to resolve the issue.

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B.Y.O.B.
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Re: LuxCoreRender v2.0alpha5 released

Post by B.Y.O.B. » Sat Feb 24, 2018 7:37 am

Thanks, that's interesting, especially
The Thea developer wrote: Our solution produces smooth renders even for very low-poly models with only the basic assumption that the subdivision is uniform (i.e. not abruptly changing).
Mistakes to Make on a Raytracer wrote:Use point x', which
represents the correct intersection point on the actual surface,
to avoid this problem (but x' is not easily computable).
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kintuX
Posts: 170
Joined: Wed Jan 10, 2018 2:37 am

Re: LuxCoreRender v2.0alpha5 released

Post by kintuX » Sat Feb 24, 2018 3:56 pm

kintuX wrote:
Sat Feb 24, 2018 2:47 am
IIRC, Corona dev. mentioned setting epsilon value to resolve the issue.
Yup, they fixed it too.


"- The terminator fix"
was implemented in Corona 1.6 Release Candidate (2017-04-07)

example from Corona forum thread > General CG discussion: CAD / NURBS surfaces vs clean topology
Image

Image

Image

& another mentioning (@ Corona forums):
- Re: Incorrect shading on imported geometry
Have you tried using the "smooth" modifier, or selecting all faces and using "retriangulate" option in editable poly tools?

Another idea is disabling the terminator fix and checking if it helps:
-go to development/experimental rollout - https://coronarenderer.freshdesk.com/su ... 2000021288
-under "terminator handling" set shadow shift to 1

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