how to get more light into the scene?

[rfollett]

This scene is lit via roof square planes, all 30000 lumens.. light does not look very real/natural..

what can you suggest to get it looking better?

thanks

[INNEO_MWo]

I would not think too much about more light in KeyShot and fix it in post

[mattjgerard]

So, as a veteran video editor that has edited most of the high end codecs from the high end cameras, this is something close to my heart.

When shooting video, you normally have 2 options, shoot in a color space that produces a visually pleasing image right in the file (REC709 for example) which will be a nearly deliverable look. Maybe small tweaks, but all in all, its a look that the client would be generally ok with.

2nd option is to shoot in some sort of ungraded color space, like SLog or LogC depending on the camera you are shooting. These images look very desaturated and washed out. Nothing looks 100% black, and generally makes clients freak out because it looks bad to them.

Now, me as an editor/compositor/colorist looks at that washed out greyish image and I get excited because I know that I can do nearly anything I want to with that image and not be limited by how it was shot, or what LUT was applied during shooting. All the grayscale values are there, all the information is there, nothing is pushed past 0% black or (hopefully ) 100% white and unrecoverable. It is an image that is very flexible in post compared to the image that was shot in REC709 and has had color curves, contrast and brightness curves already applied and are now burned in to the video and can't be changed. Color correcting and compositing REC709 files is not as easy as doing the same to LOG files, they can't be pushed as far and compression artifacts can sneak in at highly contrasting edges.

Now jump to Keyshot and 3D rendering in general. One of the goals of most people that do what we do is to get the best possible image directly out of our renderer as we can, first go, straight to print. Now, most of us know that some amount of tweaking and photoshop work is needed for almost all of the images. But nothing too drastic. With an image like the one above, its colorful, its contrasty, it has nice rich colors and deep blacks. If that is the way it came out of KS, then thats it, there's not much that can be done. The whites that are blown out are gone, can't be pulled back, the blacks that are crushed to 0% are gone, no detail in those areas. So, in photoshop, there isn't much that can be fixed.

Now, if there was a way to render out a "LOG" or ungraded version of the image above, then in post there would be MUCH more flexibility in being able to fix things. Dries showed me this when I was desperately trying to get the cloudy plastics material to transmit green light from a point source to act as an LED behind a button. I could NOT get it to work, and I posted about it. Dries posted back shortly with the image exactly the way I wanted it and had rendered an image from KS, then did some tone-mapping in PS and it was perfect. He reminded me that Keyshot is supposed to give me an image that I can work with, and its ok that it doesn't look perfect straight out, but gives me the flexibility to be creative in photoshop.

I had lost sight of the idea that there is much that can be done in PS and in post if we allow for it. I think I will be playing with the 32bit PSD file versions in order to do this, so much more color information is available in that format, especially when dealing with near white and near black grayscale levels.

So, my advice is to maybe back off the contrasty over saturated look coming out of keyshot and look to photoshop and other post tools to fine tune your image. Its more flexible, allows for quicker changes and prevents from having to re-render to change simple things.

I understand this isn't the workflow for everyone, but it certainly has saved me from having to re-render a lot because I needed to change colors slightly, or lighting and contrast tweaks for print. The trick is to know what you can and can't do in PS so that when you see your image from KS looking a little grey or washed out, that can be massaged in photoshop to look really good (and changed later if needed) or blow the whites out with a curves adjustment rather than pounding 300000 lumens of light through a fixture  in KS.

EDIT: Wow, sorry didn't realise it was that long. Morning coffee kicked in quickly....

[mcivank]

I like Matt's tip of saving out a 32bit file and softening the light a little. I just did some minor curves/color adjustment on a PNG (8bit?) and immediately started to see color banding near high lights.

How many raybounces are you using? Another post recommends atleast 30 direct and 30 indirect for interiors. I'd recomend doing a regional test render of the brightest highlights to ensure it wont be washed out in at your final render samples. I've noticed my interior renders come out slightly brighter after 400 samples than the 40-100 I preview with.

[rfollett]

I guess it is all about balance. THank you Matt for your detailed reply and others.
My PS skills are not very good... so I guess I need to brush up on them..these are about 250 samples..

[Will Gibbons]

Kudos to Matt for taking time to explain in a very simple manner, the issue of sRGB output, why it matters and what you can do to work around it in Photoshop.

I also render out to 32-bit format to push and pull tones in my images.

As for ray bounces, there is no hard, fast rule. It will always depend on the scene. Going for 30 direct and indirect is going to be overkill in many scenarios.

[rfollett]

here is the KSP file should anyone want to play...

https://www.dropbox.com/s/yq0xrvzko0nbihu/sample-room.ksp?dl=0

[zooropa]

I am experiencing something similar. The only difference is that I am not working with lights within the scene (I mean the rooftop lights).
It is a exhibition space. I have 3 walls and a roof. The 4th wall is made of glass. Imagine a rectangle box. The light can only fill the space from one of the larger sides made of glass.

The HDR light can is not strong enough to illuminate the scene. I duplicated the glass window and applied an emissive material.
Is this the right way ? I am still not satisfied. Also I have a lot of black spots ...showing that there is not much light.

I will upload screenshots soon.

Regards

Is there any tutorial for architectural lighting ?


Edit:

Render so far


Picture of the exhibition space



I think It would save some time asking to people that understands better KS in Archviz.

1. I tried to light the place only with HDR. Even raising the brightness...The outcome looks a little bit off.
2. I duplicated the glass window and applied an emissive material (rendered scene above). Definitively adds lights to the interior, but
if I try to crank the values then the surfaces next to the windows area gets burnt.
Please check the light area from the outside:

3. Rookie comment, why if my apartment, for ex, its only illuminated by the light coming from the window I can not mimic that with an HDR and forget to "fake" it with extra lights ?
4. The floor looks stained with spots (dark/light) how to correct that ?

I seen already that people did quite out-standing interior renders with KS. IS there any tutorial ?

Thanks a lot