Diffuse depth?

[Builtdown]

Hi,

I use often Direct Lightning Diffuse as the kernel for exterior shots.
Or Path tracing.

Let´s say I have a balcony with a ceiling on it. The balcony is pretty dark so I would like to add more light "bounces" to give a bit more light at the shadow areas.
I thought the diffuse depth would add more bounces and give some more light but I can´t really see much difference with diffuse depth 2 or diffuse depth 16.
Should the diffuse depth work in this case or how should I add more light to shadowed areas?
I use DayLight.

Thanks.

[ThomasVandenAbeele]

Hi!

Hard to say much without seeing the specific setting, but diffuse depth of 2 should probably take care of these bounces:

- "bounce 0" is the sunlight falling on the balcony.
- bounce 1 is light bouncing from the balcony floor up towards the ceiling and side elements (so likely going into the room).
- bounce 2 is light bouncing from the room ceiling towards wall and floor.

So with 2 bounces, the main light distribution boing into the room is well accounted for. Also, pure white wall paint reflect about 85% of the light, so I guess with gray or wood elements you probably have less than 50% of the incident sunlight power working inside the room. Take away a big part that can't enter through the window "hole" and it's safe to say that if you want a shot where both the exterior and interior appear well lit, you're screwed Adding bounces won't help that much because there's simply not enough light in there to make a decent contribution.

This is also what happens in reality: if you shoot a nice interior shot, the exterior will look overexposed through the windows. Conversely, if you take a nice garden picture, indoors areas will look very dark.

Hence an often used solution, both in real life shoots and in 3D: add some fake light to shadowy areas.

[Builtdown]

Thanks,

I have hard time achieving this kind of lighting situations :
https://upload.wikimedia.org/wikipedia/ ... _Wales.jpg

Hard sun light making dark shadows, but beautiful lit terrace walls and ceiling.
If I would make this kind of scene, the shadows would be too dark and the walls would not be lit like this. I thought adding more bounces would help but I guess not?
If I adjust gamma or exposure, I get nicer looking shadows but it washes out the other areas.

Any other tips?
And adding fake lights is not a solution with a "true-life-renderer".

[3dreamstudios]

Might be the surfaces you have setup? Changing the bounces does affect the lighting in the scene as shown in this test. For the soft shadows you may want to adjust the SIZE of the sun, I think that will make it softer in places...
Also like you mentioned gamma and exposure will change how the final image looks. Your sample image looks to be blown out on the highlights...therefore showing more detail in the shadows....if it were not blown out on the highlights the shadows most likely would be darker and maybe not as nice looking ? Just some thoughts...

[ThomasVandenAbeele]

Agreed with the poster above: the shadows are rich because the sun light spot on the floor and bottom of wall is washed out. No time tonight, but I'll set up a simple scene for you tomorrow to get you started.

Also: you are right in that you can not add fake lights in physically accurate setups, but then again photoshoots use a lot of lamps and bounce cards outside of the camera view so don't hesitate to use those. Just remember: if it looks right, it is right - I've lost too much time trying to do things in what I thought was "the right way", only to find out that all the pros use the "wrong way" because it just works.

[FrankPooleFloating]

^ Agree with Thomas. Sometimes you add a light and fake it, rather than hours of bs work. Just like I often spend 5 minutes cloning/spot heal brushing a handful of hot pixels in PS, rather than cook a render for hours on end. If it works, it works.

[ThomasVandenAbeele]

Here's a quick render test that confirms my suspicion: there's plenty of light to bounce around because you have a big patch of sunlight on the floor that bounces up nicely. Even with one bounce (diffuse depth 2, on top) you get plenty of light on ceiling and walls, and with three bounce (diffuse depth 4, bottom image) everything is very nicely and evenly lit. Surfaces are coloured RGB 200, 200, 200 (out of 255), so about 80% light redistribution, but you can definitely go lower and still have nice lighting on the ceiling.

I guess in your scene the amount of light that can be bounced up to walls and ceiling is just too small, due to the specific geometry you have.

Scene file attached. By the way, if you post your work in progress people will be able to help you out MUCH more.

[Builtdown]

Thanks,
I will look into this. And probably send some scene that I have problems with.

What I often have problems with is the dark shadows. With Lightwave renderer you can change the shadow color but I know that it can´t be done with Octane.
What my clients want is a nice sunshine but no dark shadows. Something like this : http://41.media.tumblr.com/tumblr_mbfan ... 1_1280.jpg

Hard to achieve?

[FrankPooleFloating]

Have you played around with render layers and new Octane EXR PS plug? You can control shadows, reflections etc separately.

Another alternative is do a render with Cast Shadows turned off on everything in main render, then do a Material Override render with only shadows (entire scene white except shadows). Then just comp in PS and make shadows Multiply. Plus you could toss in an AO render, to get some more shadows in corners etc. But the new Render Layer stuff is much easier.

[Builtdown]

Sure, I have made that Cast shadows OFF render but that takes usually even more time than a beauty render so not a good solution.

Render Layers would help, but I would like to get a solution with a single render.
Because it is possible to get a photo like this with a camera, I would like to get the same with Octane...