Interior lighting test

[Harys1]

Hi,

I am new to Corona, but after two days of testing I have to say that it looks really great.
Here is my interior lighting test. It's quite simple scene with only Corona Sun and Sky (and one Corona light above the table). In windows, there are planes with glass mtl with Thin and Portal checked (at first, it was solid "triple-glass" window, but it seemed like a problem and times wasn't so good, so i put there just one plane).

Render times on my i7 cpu was about 15-20min for 1200x800 render, but maybe it's already "too clear", i think in only 8-12min it looked quite good. I used default settings.

Any beginner tips about lighting and settings are welcome, (by settings, I mean in which cases is good increase or decrease same value and how much, because I don't have deep understanding how it all works :).

PS: Excuse my English :)

[Ludvik Koutny]

It's quite simple actually. If you do not understand settings then there's no reason to touch them. Defaults work just fine, so you can simply let the render cook till it looks clean.

Also, triple glass should not be much of a problem problem, if you use 3 planes with thin mode. Just do not use them as portals. That would be a HUGE problem. if there is more than one polygon in a window as portal, then it can break the scene pretty quickly.

[Harys1]

thanks for reply :)

[romullus]

It's quite simple actually. If you do not understand settings then there's no reason to touch them. Defaults work just fine, so you can simply let the render cook till it looks clean.

Also, triple glass should not be much of a problem problem, if you use 3 planes with thin mode. Just do not use them as portals. That would be a HUGE problem. if there is more than one polygon in a window as portal, then it can break the scene pretty quickly.

I was under the impression that limit on polycount in portals, were removed some time ago. Am i wrong?

[racoonart]

He's not referring to the polycount. It's a problem if it's 3 polygons stacking up on each other like this ||| (sideview). Your portal planes can have several polygons, but you mustn't use geometry like a box or in this case 3 planes on top of each other.

[Ludvik Koutny]

Limit on polycount yes. Although it still does not make sense to make portals highpoly. I am talking about situation where there are two or more portals covering an opening. That will mess things up.

I also think that having portal checkbox in material was a really bad idea. Because it will confuse more people than it will help.

[Romsy]

update of Harys1 work progress:)

[londonvisuals]

I think that those look very promissing. As a side note I think that You should pay attention to saturation of the materials. I'm under an impression that many of the woods are slightly oversaturated.

[Ludvik Koutny]

Background mountains are HDRI, or just some mapped geometry?

[Romsy]

londonvisuals:
I think that Tomas (Harys1) used some color boost in photoshop. I agree that it seems to be a bit more saturated.

Rawalanche:
Tomas will answer after he will wake up:)
I´m working on the same interior in Vray for comparation. I´ve just posted in the morning what I have found in his output folder:))

[Harys1]

Background is just image added in PS, there is no HDRI only corona Sky, it's really nothing special. And about postpro, I made little color correction, maybe it's too saturated. I'm not so good at it yet (btw Pavel (Romsy) is :).

I have a question, is there any way how to make AO. In Vray, there is a checkbox in Render setting, but i didn't find something like that in Corona. Personally I don't like those very dark (almost black) corners, but for example in render with green chair little bit of AO would help.

[Ludvik Koutny]

Background is just image added in PS, there is no HDRI only corona Sky, it's really nothing special. And about postpro, I made little color correction, maybe it's too saturated. I'm not so good at it yet (btw Pavel (Romsy) is :).

I have a question, is there any way how to make AO. In Vray, there is a checkbox in Render setting, but i didn't find something like that in Corona. Personally I don't like those very dark (almost black) corners, but for example in render with green chair little bit of AO would help.

Yes, you can get AO, but no, you should not use it.

You are rendering semi-bruteforce GI, so the detail is there. Most of the people use AO wrong. AO is not something that improves contact shadows. It's a legacy method to enhance flat ambient lighting from times, where there was no such thing as global illumination, and then it was adopted to enhance primitive indirect illumination methods as radiosity or final gathering.

But for modern methods, such as properly written irradiance cache, or brute force rendering, there is  no reason to use AO.

If you are lacking contact shadows, like in the example of room with green chair, then it means your Albedo (overall material brightness) is too high. Sheet of white paper is usually about RGB 220, very white walls are usually RGB 200-210.... fresh mountain snow is about 230... 

People often do a mistake of making materials a lot brighter than they really are. So check your materials for super bright values. Even your wood floor may be a bit brighter than it should be. You can fix that by setting output amount in your bitmap to for example 0.8. That's what usually produces that washed out flat lighting look. I would never go over RGB 230 white.

And high albedo doesn't just make renders look unrealistic, it also slows down the rendering because russian roulette algorithms are having hard time.

So check that... and if it get's a bit darker after fixing material, just compensate for it with exposure.

Lastly... for background planes, environments behind windows and such... use CoronaLightMTL with disabled emit light option. That's it... it will not cast shadows nor receive any shading, so it's ideal for background plates behind windows.

And try to avoid fakes, like disabling shadow casting and such, because they slow down rendering as well.

[Harys1]

wow, thanks for your answer

About that albedo I read a little bit here on forum, so I tryed do not make RGB values bigger then 220.  But I'm not sure, if it applies only for diffuse component or it's also related with reflection and refraction, so I shouldn't have in refl. bigger values than about 220. Sorry, if it's stupid question :)

[Ludvik Koutny]

You should not have absolute reflection, but you can have reflection of say 240-250 for perfect mirror. You should not make for example very white materials with very high reflection. So say white ceramics vase should be diffuse RGB 210, Reflection RGB 160, and reflection IOR 1.55.

And if Albedo of your materials is OK, then you can try to decrease exposure little, and increase contrast, but if it looks that way, then it's probably the way it would look in real world. You have a perfectly sunny day during lunch time in a bright white room with bright floor and no furniture to absorb light oriented to the sunlight and a chair with quite thin legs. Those are not conditions for some significant shadowing to occur.

If you even after this want to use AO, then there are two ways:

Put CoronaAO map in the TexMap render element, render an AO pass, and composite it in.

Or plug CoronaAO map to the diffuse slot of your floor material, and chair legs material. Then put original diffuse textures in the unoccluded color slots of CoronaAO. Then you can also use Include/Exclude feature of CoronaAO map to include only floor object as occluder for chair legs material, and chair legs as occluder for floor material. This way, you will get occlussion only between the two without occlussion from walls around the edges of your floor .