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Re: LuxCoreRender v2.1alpha2 released

Posted: Wed Jul 04, 2018 9:42 am
by Dade
kintuX wrote:
Mon Jul 02, 2018 8:54 pm
Using standard (old) strategies the catcher plane stays barely visible (1),
while using DLC strategy plane is fully invisible but strange splotching appears in shadow area (2).
I have never tried the combo shadow catcher and DLSC, I'm going to check what is going on.

Re: LuxCoreRender v2.1alpha2 released

Posted: Wed Jul 04, 2018 10:13 am
by marcatore
About the filtering of the lightcache samples, I mean something that can smooth the image area like the one you see over the table in this image.

http://forums.luxcorerender.org/downloa ... &mode=view

It seems that there are some "circle" with different brightness and I'm thinking to something that bring some samples with a distance rule and smooth together to smooth the transition from a "circle" to another one.

Is it something that had sense?

Re: LuxCoreRender v2.1alpha2 released

Posted: Wed Jul 04, 2018 5:56 pm
by B.Y.O.B.
As far as I understand it, the light cache only adjusts the probabilities of a light being sampled and is still unbiased.
The phenomenon in the linked image might be startup bias or something else caused by not enough samples (but it is a bit hard to tell without a ground truth image).

Re: LuxCoreRender v2.1alpha2 released

Posted: Wed Jul 04, 2018 9:19 pm
by Dade
B.Y.O.B. wrote:
Wed Jul 04, 2018 5:56 pm
As far as I understand it, the light cache only adjusts the probabilities of a light being sampled and is still unbiased.
Correct.
B.Y.O.B. wrote:
Wed Jul 04, 2018 5:56 pm
The phenomenon in the linked image might be startup bias or something else caused by not enough samples (but it is a bit hard to tell without a ground truth image).
It is noise, a (huge) different level of noise. DLSC fallback to standard log power light strategy when a valid cache entry is not avilable for the point I'm rendering. It is very noticeable. Look, this is a scene with a well populated cache (1 sample per pixel):

im1.jpg

and this is the same scene with not enough cache entries:

im2.jpg

The surfaces without a valid cache entry are very easy to spot due the HUGE difference in noise. It is still unbiased so it will converge to the same result but in practice they look as artifacts.

Re: LuxCoreRender v2.1alpha2 released

Posted: Thu Jul 05, 2018 6:55 am
by marcatore
So probably it's not something like the Vray lightcache

https://docs.chaosgroup.com/display/VRA ... e+Settings

In that doc there is the "pre-filter" explanation
"Pre-filter – When enabled, the samples in the light cache are filtered before rendering. Note that this is different from the normal light cache filtering controlled by the Filter parameter, which happens during rendering. Prefiltering is performed by examining each sample in turn, and modifying it so that it represents the average of the given number of nearby samples. More prefilter samples mean a blurrier and less noisy light cache. Prefiltering is computed only once after a new light cache is computed or loaded from disk."

I know that Dade that you don't have the vray source code ( :) ) so my question is a bit useless but do you think it's completely another kind of algorithm?

Re: LuxCoreRender v2.1alpha2 released

Posted: Thu Jul 05, 2018 7:21 am
by Dade
marcatore wrote:
Thu Jul 05, 2018 6:55 am
I know that Dade that you don't have the vray source code ( :) ) so my question is a bit useless but do you think it's completely another kind of algorithm?
It is different, V-ray sounds like a classic photon mapping where you can use the photon map to render direct light. Like B.Y.O.B. wrote, DLSC is only changing the probability to sample specific lights.

Re: LuxCoreRender v2.1alpha2 released

Posted: Thu Jul 05, 2018 11:38 am
by kintuX
Dade wrote:
Wed Jul 04, 2018 9:42 am
kintuX wrote:
Mon Jul 02, 2018 8:54 pm
Using standard (old) strategies the catcher plane stays barely visible (1),
while using DLC strategy plane is fully invisible but strange splotching appears in shadow area (2).
I have never tried the combo shadow catcher and DLSC, I'm going to check what is going on.
After further tests i found it's a corner case. Happens only when both: Sun & World (HDRI, Sky or Flat Color) are used at the same time. Separately everything works as expected. & Those artifacts look like are from samples only on shadow's edges.

e.g.
resultsALL.jpg
EDIT1
Oh, i should have pay more attention - i assume it's related to:
Dade wrote:
Mon Jun 11, 2018 4:24 pm
...
Indeed, I have to handle hard shadow borders careful but I have an idea for that problem.
...
@ DLSC (aka LC pt.I)

TYVM for the great work and effort you put into.