DLCS Explained

Discussion related to the Engine functionality, implementations and API.
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Sharlybg
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DLCS Explained

Post by Sharlybg » Mon Oct 22, 2018 10:21 am

Hi ! As there already a lot of project starting to use DLCS feature i open this thread to let developper Give complete information on how each DLCS settings work and impact rendering. Maybe also the place to know wich parameters need to be expose or which one can be automatically be computed with user given Data so we avoid hyper trial error learning process and also too much setting complexity (like Old Vray).
After getting clear understanding of that The Wiki/Tutorial phase will be more effective. So let Demistify DLCS together :

1/ What are all DLCS available parameters ?

2/ What each of them does ?

3/ Which one could be automatically computed ?

4/ Any possibility to have live render efficiency number to clearly see when to use and when DLCS outperform other Light strategy ?
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Sharlybg
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Re: DLCS Explained

Post by Sharlybg » Tue Oct 23, 2018 11:35 am

Dade and BYOB :?:
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Dade
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Re: DLCS Explained

Post by Dade » Wed Oct 24, 2018 10:40 am

Your a mostly going to face 2 types of problems when using DLSC:

1) some area can include a LOT of noise if it is not covered by a cache entry (note noise, not artifacts);

2) some area can be in shadow while it shouldn't if the cache entry has wrong list of visible lights attached;

The problem #1 can happen when you are rendering a scene with a scale significantly different from the one of the small room (the default cache entry radius is 0.15m, 15cm). For instance, if you are rendering a city, you will have to increase the radius a lot otherwise you will end with problem #1.

The problem #2 can happen when you are rendering some "hard" to find light source. The default number of samples used to establish if a light source is visible or not is 12 (aka the warmup parameter). It is a very low value, it can easily lead to false result. If you have problems like #2, just increase the value until when the artifacts are gone (indeed, this will increase the pre-processing time).
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Sharlybg
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Re: DLCS Explained

Post by Sharlybg » Wed Oct 24, 2018 11:19 am

Dade wrote:
Wed Oct 24, 2018 10:40 am
Your a mostly going to face 2 types of problems when using DLSC:

1) some area can include a LOT of noise if it is not covered by a cache entry (note noise, not artifacts);

2) some area can be in shadow while it shouldn't if the cache entry has wrong list of visible lights attached;

The problem #1 can happen when you are rendering a scene with a scale significantly different from the one of the small room (the default cache entry radius is 0.15m, 15cm). For instance, if you are rendering a city, you will have to increase the radius a lot otherwise you will end with problem #1.

The problem #2 can happen when you are rendering some "hard" to find light source. The default number of samples used to establish if a light source is visible or not is 12 (aka the warmup parameter). It is a very low value, it can easily lead to false result. If you have problems like #2, just increase the value until when the artifacts are gone (indeed, this will increase the pre-processing time).

NIce thank you for your explanation.

So the end user just need theses only two parameters to work with ?

. Cache entry radius : The bigger the scene the bigger the number

. Warmup parameter : The harder light source can be find higher the number should be

So is there any reason to keep other settings available ?
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Dade
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Re: DLCS Explained

Post by Dade » Wed Oct 24, 2018 2:25 pm

Sharlybg wrote:
Wed Oct 24, 2018 11:19 am
So the end user just need theses only two parameters to work with ?
99% of times, yes.
Sharlybg wrote:
Wed Oct 24, 2018 11:19 am
. Cache entry radius : The bigger the scene the bigger the number
And smaller scenes and smaller is the number.
Sharlybg wrote:
Wed Oct 24, 2018 11:19 am
. Warmup parameter : The harder light source can be find higher the number should be

So is there any reason to keep other settings available ?
Corner cases but they can be under and "Advanced" tab as usual.
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B.Y.O.B.
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Re: DLCS Explained

Post by B.Y.O.B. » Wed Oct 24, 2018 2:38 pm

Sharlybg wrote:
Wed Oct 24, 2018 11:19 am
Cache entry radius : The bigger the scene the bigger the number
Could we automatically compute this? (Maybe from scene bounding box)
If yes, we could show a multiplier to the user for those cases where the auto-computed value has to be adjusted.
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lacilaci
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Re: DLCS Explained

Post by lacilaci » Wed Oct 24, 2018 3:06 pm

btw, was this issue (viewtopic.php?f=4&t=483&start=20) with skylight fixed?

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Dade
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Re: DLCS Explained

Post by Dade » Wed Oct 24, 2018 3:26 pm

B.Y.O.B. wrote:
Wed Oct 24, 2018 2:38 pm
Sharlybg wrote:
Wed Oct 24, 2018 11:19 am
Cache entry radius : The bigger the scene the bigger the number
Could we automatically compute this? (Maybe from scene bounding box)
If yes, we could show a multiplier to the user for those cases where the auto-computed value has to be adjusted.
Not really: you can still have the model of a city and just be inside a room (so using the scene bounding box would be very misleading). It is also related to the "size" of observer/camera: an ant would need tiny values while a elephant would use larger one (i.e. it is related to the portion of the scene you are looking at).
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Re: DLCS Explained

Post by Dade » Wed Oct 24, 2018 3:26 pm

lacilaci wrote:
Wed Oct 24, 2018 3:06 pm
btw, was this issue (viewtopic.php?f=4&t=483&start=20) with skylight fixed?
It is exactly problem #2 listed here.
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Re: DLCS Explained

Post by B.Y.O.B. » Wed Oct 24, 2018 3:50 pm

lacilaci wrote:
Wed Oct 24, 2018 3:06 pm
btw, was this issue (viewtopic.php?f=4&t=483&start=20) with skylight fixed?
In the next release, you will have the "warmup samples" parameter available to fix it.
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