sIBL usage - balancing the lighting and sky

Here we discuss topics that are common for all versions of Reality, without distinction of platform or host
RLSprouse
Posts: 56
Joined: Sat Mar 02, 2013 10:07 am

sIBL usage - balancing the lighting and sky

Postby RLSprouse » Fri May 27, 2016 6:03 pm

I am attempting to learn how to use HDR, IBL, sIBL technology with Reality and Luxrender. I have purchased some high-quality sIBL sets from the Dutch Skies site, so I know I am using high-quality stuff.

I watched Paolo's video tutorial, and I am able to load the sIBL set just as shown. The problem I am having is that when I adjust the camera settings to get a nicely lit character, the sky goes *very* dark. What is the best/easiest technique to balance the lighting in the scene with the brightness of the sky when rendered by Lux? Is it simply a matter of inserting a diffuser above the character? Won't that soften the shadows too much, and destroy the simulation of sunlight?

User avatar
Marcel2586
Posts: 439
Joined: Sat Mar 05, 2016 7:42 am

Re: sIBL usage - balancing the lighting and sky

Postby Marcel2586 » Fri May 27, 2016 6:45 pm

Offtopic and no answer to your question,
I visited the site and was happily surprised that the pictures taken from the beach, are just 500 meters from my home. The mole you see is the harbor entrance and i live at the harbor of Scheveningen.
this would be funny if it weren't happening to me :shock:

RLSprouse
Posts: 56
Joined: Sat Mar 02, 2013 10:07 am

Re: sIBL usage - balancing the lighting and sky

Postby RLSprouse » Fri May 27, 2016 7:11 pm

Very cool, Marcel. This guy must be a neighbor of yours. :-)

I have been experimenting with my idea of placing a diffuser above the character, and I found that even at 99% opacity, the character is still too brightly lit relative to the background, and as I anticipated, the shadows have gone soft. But worse yet, there is a horrible dark pattern appearing on her skin. See the attached. (Or not... it seems we cannot upload an image here?)

I must be doing something horribly wrong... or is there simply too much dynamic range in the image I am trying to use?

~ Russ

pciccone
Site Admin
Posts: 1803
Joined: Mon Feb 25, 2013 6:25 pm

Re: sIBL usage - balancing the lighting and sky

Postby pciccone » Fri May 27, 2016 11:00 pm

Russ, can you give us some example, with exposure settings and light config?
--
Paolo

RLSprouse
Posts: 56
Joined: Sat Mar 02, 2013 10:07 am

Re: sIBL usage - balancing the lighting and sky

Postby RLSprouse » Sun May 29, 2016 7:49 am

I don't see an easy way to include an image in a post here. Do we really have to upload images to a web host, and then link to them? Or am I missing something that should be obvious?

User avatar
Marcel2586
Posts: 439
Joined: Sat Mar 05, 2016 7:42 am

Re: sIBL usage - balancing the lighting and sky

Postby Marcel2586 » Sun May 29, 2016 8:09 am

RLSprouse,

Click on the Full Editor & Preview button.
You will get an extra option under Post a Reply.
If you click on the tab Attachments you can upload images if you click on the Add files button.
No need to upload it to other websites. If it is not to large then you can upload,if it is large as, animations, use dropbox and place the link in your message
step 1.jpg

Step 3.jpg

Step 2.jpg

step 4.jpg
this would be funny if it weren't happening to me :shock:

RLSprouse
Posts: 56
Joined: Sat Mar 02, 2013 10:07 am

Re: sIBL usage - balancing the lighting and sky

Postby RLSprouse » Mon May 30, 2016 3:02 pm

Okay, here is an example of what I am seeing. The attached render is V7 with an sIBL loaded for lighting and background. I am also including the preview .jpg for the sIBL set I used. It is one of the sets in the "Dutch Skies 360° HDRI – Volume 1 Reloaded" set I purchased.

In Reality, I have the camera set to ISO 100, 1/125 sec., f/4.0. the IBL is the only light in the scene.

Marcel, thanks so much for taking the time to show me how to post images!

~ Russ

V7 Dutch Sky test 4.png

DS360_Volume_1_Super_Bonus_16k_Prev.jpg

pciccone
Site Admin
Posts: 1803
Joined: Mon Feb 25, 2013 6:25 pm

Re: sIBL usage - balancing the lighting and sky

Postby pciccone » Mon May 30, 2016 3:06 pm

Hi Russ.
The result that you have is because your lights are unbalanced. The light falling on the subject is too bright compared to the IBL. Go to the Light groups tab in Lux and raise the brightness of the IBL light.

Cheers.
--
Paolo

RLSprouse
Posts: 56
Joined: Sat Mar 02, 2013 10:07 am

Re: sIBL usage - balancing the lighting and sky

Postby RLSprouse » Mon May 30, 2016 3:21 pm

Paolo, I don't understand. There is only one light - the IBL. How will raising the brightness of the IBL effect the balance of the subject and the background? I've given it a quick test, and it effects the exposure, so I had to change the camera settings to compensate, but then I end up with the same result.

RLSprouse
Posts: 56
Joined: Sat Mar 02, 2013 10:07 am

Re: sIBL usage - balancing the lighting and sky

Postby RLSprouse » Tue May 31, 2016 12:29 pm

I did another experiment, and have come up with an hypothesis. I spun the IBL sphere 180 degrees so the sun was coming from behind the character, and got the result shown here. My hypothesis is that this IBL has such extreme dynamic range that Luxrender cannot handle it. I did not realize that you could have too much dynamic range in an IBL, but that seems to explain what I have been experiencing.

So this leads to some additional questions. Is there a way to "tone down" the dynamic range of the IBL image? Is there a way to measure the dynamic range of an image? And what is a reasonable dynamic range that Luxrender can handle without getting these extreme results?

Any thoughts or assistance would be greatly appreciated.

~ Russ

V7 Dutch Sky test 6.png


Return to “General”

Who is online

Users browsing this forum: No registered users and 2 guests