Sky and HDRI

[ozwald]

Hello friends.
I have a doubt when I shine with Sky and with hdri.

For interior lighting when using sky we know that the portals
of light help to reduce the noise and the render time is short.

But!! when using HDRI sky the lighting portals do not work
to reduce the noise.
In this case we can do to not have so much noise and
download render time?

[burnin]

To elaborate further, please provide some factual comparison results of your tests (images, statistics and possibly a scene file).

[ozwald]

It is very simple to see what I say.
in an indoor scene with one or two light inputs, (windows)
illuminate with a Corona sky and put portals of light.
Do another test with an HDR remove the light portals
and you will see an increase in noise.
What I want to know if there is a way to not have as much noise with an HDR

[TomG]

Why would you remove the light portals with the HDRI? Their function remains the same whether using a Corona Sky or an HDRI (to guide the sampler in where to focus processing to reduce noise). Removing the portals should indeed increase noise, whether a sky or HDRI is used. Let me know if I am missing what you are describing :)

[TomG]

Your first post describes the issue as still seeing noise if the portals are left there with an HDRI - but could be that the HDRI is just a poor quality one anyway. Impossible to say without seeing renders, and perhaps having the scene to have a look (https://corona-renderer.com/upload for either the scene with the HDRI).

You don't mention if this is with all HDRIs, or just one specific one, that would be good to know too. If you can't share the scene, would be good to at least see grabs of the scene set up (to make sure the portals are set up correctly), and renders of the result - based on your first post, it sounds like the image rendered with an HDRI looks just the same with or without portals?

[ozwald]

before they said that the light portals only
could be used with Corona skies and not with HDR
that's why it was my confusion.
However, I've still used them with HDR because I forgot to remove them
but!! likewise the noise was greater with HDR than with crown sky

[TomG]

Noise being greater with an HDRI vs Sky may not be surprising (the Sky is fairly even lighting, while an HDRI can vary greatly in lighting from specific directions unless it's a clear blue sky :) ). The question is, are you getting more noise with an HDRI with portals, vs an HDRI without portals. That shouldn't happen - but "more noise with an HDRI rather than sky" is reasonable I would say, depending on the HDRI in question.

Let me know which one it is :)

[ozwald]

Of course, the noise with the HDR is greater than using corona sky.
Now I understand and you are right about the illumination of the sky is uniform and by
that less noise.
However!! I have not done tests with portals in HDR because as I told you
in the notes it came out that it should only be used with sky.
since you tell me that if it can be used in the same way with HDR I'll do tests
thank you very much

[TomG]

You're welcome, and glad we have the confusion cleared up!

Do you know where those notes are about only using it with the Corona Sky? Just in case anything needs updating or clarifying any place. Thanks!

[ozwald]

I think that note came earlier in the information of the
material.
I really have not read the new information, I think it has changed
my mistake was not to read, and to think that the previous information was maintained

[TomG]

No worries! If you do find that information any place, let us know so we can be sure everything is updated :) Things have changed quite a bit over the last year or so, and it's good to have anything where we have old info pointed out to us, just in case!