I've been having pretty good and relatively fast results when rendering objects in an open environemnt with HDRI for lighting (+Caustics,  -Light Through Transparency, +Indirect Lighting), but my tests reveal that the same will not work for an indoor scene.

What I like about the HDRI and Indirect Lighting is the natural bounce I get using this method. But with over 3 hours for a low resolution test render of a simple base scene, it is clearly not going to work out for the scene I have planned. Not if I want it to finish rendering this year.

The effect I am looking for is the softened shadows from the window freames + the bounce filling the room with natural ambience (darker in corners, bends and small places like furniture openings, lighter in open wall segments).

I was able to get the soft shadows from the windows by using a spot light with soft shadows (best or they get line separations) - 3min render.

I was able to get the amient bounce by using a white glow plane instead of the windows and rendering the Indirect lighting at 100 %, but that is a 4 HOUR render on the same small size!

I can kind of get what I want by combining the 2. But once I set up and populate my scene, the render times will get prohibitevely expensive, especially for the resolution I need.

I am attaching the desired result combination here and I will attach the components in response messages.

HDRI for background, but no Sky Light or Indirect Light is activated, so it has no effect on the lighting.

(The glow plane looks black because it was actually set to 100% tranparency, but having the white glow still gave me the lighting I needed even when the panel itself didn't render at all.)

I've had success with my fake gi rig that I use for out doors, adapting it for indoors -

adapted rig =

4 spots lights p0inted downwards at 45 degrees from all compass points - say at 15 to 25 percent strength and 30 percent shadows - but chose a colour not white, use a large angle

then group these

then duplicate, and point them up, chose another colour(s) to simulate reflected light from the floor and walls, say 8 percent light, no shadows,

do a few renders

then decide where your major light source (s) will be and introduce this last light(s) maybe with soft shadows

the percents need to be tweaked a lot but render times much faster and you have more control of most parts of the light setup

I've been painting a lot of bad still lifes recently, but it's interesting how faking a reflected light (needs to be coloured usually) will add a feeling of veracity

Hi I think it looks pretty good, - the faster render times mean you can experiment with  tweaking your lighting more - and positioning objects etc

I forget to mention the fall off for the spots - that will solve those ugly overlaps

I guess you know this, but if you select eg all the ceiling lights then you can fiddle with their parameters en masse

you also have the option of using anything glows on your rendering camera for a slight bit of filllight when you are rendering with the objects in situ

It's got about 70 lights at various settings, and It's still not as natural as I'd like it to be...

Is there any way to use the Carrara calculated bounce, but reduce the quality/component settings to speed it up? Or to use a simplified proxy environment to calculate the light map, maybe? Would any of these tricks work?

sorry I don't know these things :(

I always work back from the quickest render time to an acceptable image - rather than the other way around so I don't muck around with the sexy stuff!

I'm always relying on post work, ( i render a coverage and shadow layer as well)

I  reckon that image (last) taken into ps and sharpened would be pretty good, also adjusting the levels would help in post, plus I use oloneo hdr on single images and  that tweaks them as well

but it's not the answer you are looking for sorry 

After working with this for a bit all I can say is, I have that model lol

Being an advocate of in scene lighting I set it up completely differnt. I duplicated the overhead light and set anyhting glows to the light cover meshs; 8. 

I've set it up as described here but I can't get render times down. It needs soft shadow lighting and the minute I check it my render time shoots up.

what model is it? or it comes in the browser? 

It's a freebie .obj from some place. I'm a freebie model mesh downloading junky, so how knows where lol

"classroom"

thanks, I haven't even downloaded stacks of stuff that've bought from daz, seems like a good buy at the ime, I guess it's like someone addicted to shoe buying 

Is the archived forum gone for good?

This was a freebie by a Carrara artist, whose freebies were absolutely amazing. But I am terrible with names and I no longer remember his forum name. This is horrible, because I can't find the cashed versions of the archived forum threads anywhere. I think the nickname had a "5" in it, but as I said, I am terrible with names. I went back to the zip files he provided, but there aren't any readme files or notes, just the objects :(.

This is all wrong, because now I won't know how to give proper credit! :(

If you remember the person, please help me out!

Thanks, someone will know somewhere ,!

I would set it up to be as natural as possible and then dial the GI lighting values to get what you want.

1.)  Use a distant light with the soft shadows jacked up big.  Start at 100 ft (for the soft shadow radius) and increase it until you get what you want.

2.)  Put in a skydome using a bi-gradient in the background.

3.)  Turn on the skylight and indirect light in the GI settings.

Then dial the strength of the lighting for each of the two GI effects and see if that works for you.

The result should actualy be physically realistic.  If it's too dark, that means that you need more lights inside just like real life.  Add them.  That's why we have lights indoors.  If you have to have lights inside, it won't look weird.

As you can see, with just one light, the results along the ceiling and sections of the room not in the light are not well lit.  However, I think it's fairly realistic and if you want more light, add lights to the scene that you would expect hanging from the ceiling like real lights (fixtures and everything).

I did reduce the blur diameter away from 100 though.  I used something much more along the lines of 35.

Indirect lighting set to 400.  Skylight set to 50.

You can see the blue of the sky on the floor (just like it should be).

Wow! This looks very impressive (And great quick modelling, by the way! Bravo!)

What were your render times for this image? (And what are your system specs? so I'd know how to approximate that for my own.)

My main problem is really in the render times. I want a classsroom full of furniture, props and human figures, fully clothed. Even if I use proxy figures for the ones near the blackboard, it's still a LOT of stuff for the light to bounce off and slow down calculations.

Kixum, that scene comes with a nice over head floresent fixture. Depending on how you import it; and I like it divided by mesh/shader as much as possable, the light will come in 2 parts, the fixture and the cover.

I used anything glows; it has problems with meshs some times but not in this scene, and a rather obnoxious render time. Now I have the version of this I was working on in a scene but it is a minimal lighting scene, after dark in the school and some kids that have snuck in to see the ghost teacher. So this is a new scene, moderate settings, and an hour render time.

Can you see the light I missed setting softshadows on lol

is this what you are after?

Andrew, my scene will have more stuff in it... Your image lookg good, but I don't see the kind of shadows lurking in the corners natural bounce that I am looking for...

Stanley, I know that people have fooled Carrara into doing good quality lighting in less time, so I am hoping to see if anyone has good at least some optimization ideas. Maybe there is a setting somewhere which is not strictly needed and can be skipped without much quality drop, but with speed improvement. For example, turning "light through transparency" off really does shave off a lot of render time, so if a scene can be set up without it, it works marvelously. There is also "Full Raytracing", which gives some quality improvement, but it is so insignificant that it's practically never worth the render speed price. So I am looking for other options I can save render time on.

Kixum here is getting pretty awesome results, so I'd like to know how long it takes and what the settings are.

Alright, let's report some statistics.

If you're curious, I built this scene in 90 minutes.

I am rendering on an I7 4 core dual threaded machine (so C thinks it's 8 heads).  It's a 2.1 GHz with 4 Gig RAM.  My machine is actually an ASUS gaming laptop (It's what made sense when I was living in my beeny apartment in Japan.

The first image I rendered was with just the one light (the distant light) and the skylight.

There are other important things to consider.

I am running with soft shadows set to best.

No interpolation in the GI rendering settings.

0.5 pixel accuracy.

Best antialiasing.

2 pixel shadows

Best GI at 2 pixels

So yeah, this render is basically jacked up to the maximum.

The first scene rendered in about 70 minutes.

The second render adds the three ceiling lights.  These lights are ring lights surrounding the pole from the ceiling and setting inside the "bowl" of the light such that the lights are only able to hit the ceiling.  This pushes all of the light contributions down in the room to be from indirect lighting.

I also felt that 400 on the indirect lighting was blowing out the render too much so I turned it down to 300.

So, the second render is with four lights and the skydome.  It took about 2.5 hours with everything jacked up to the maximum like before.

Other things to consider:

If you put something in this scene which has any significant surface texture (bump stuff), it's going to cost you in render time.  The more objects you put in, the more the precalculations for the lighting seem to take.  With four lights, the shadows also become more cumbersome.

I should also mention that I actually have glass in my windows with light through transparency on.  If I simply got rid of the glass, I would probably reduce my render times by 25%.  I have reflection turned on and that means that C has to render things from multiple angles to get that reflection working.

Oh yeah, it was a 1440X900 render.

Forgot that.

With things all the way to the max, I would guess that I could back off on these render settings and probably get almost the same result in about half the time (just a guess).

Turned off raytracing.

Turned off light through transparency.

Accuracy set to 1 pixel, antialiasing set to good.

GI set to Excellent, 4 Pixels

Render time, .......

12 minutes.

No doubt the quality is affected but you can assess it for yourself.

Another thing to note is that I have re-saved these images with JPG compression set to 20.  So, some of the artifacts you may be seeing is from that compression.

Kixum, your results here are beyond amazing. Either your system is very far ahead of mine (possible, since this thing is about 5 years old now), or you are doing something that I need to learn how to do :).

Could you share your scene file with me somehow? So I could run a render and compare the times I get with the same settings on the same scene?

(If you don't want to share it publicly, maybe you could e-mail it to me, I am antara.nn on Gmail)

The quality of the light in your scene is exactly what I am trying to get, but I am not getting anywhere near it within the same render time scopes. I was able to fake it though, using Ambient Occlusion only for Indirect lighting and then faking the bounce.

I will post the result when the big image renders.

I've posted my scene in the freestuff.  When it gets approved, then it will be available.

As a freestuff item, maybe a bunch of people can get some use out of it.

I hope it helps!

Hey!  I'm a coordinator!  I can approve it!

Go and get it!

In the mean while I rendered a fake bounce scene (So my spot for the window shadows, plus a huge amount of low intensity lights all over the place to fake bounce - about 75 of them. I didn't alter their color yet, so the whole thing is still gray, but I plan to change that eventually to have a more believable color bounce.) with AO only for indirect light. My file (not very small this time, but not full resolution either yet) rendered in 33 minutes. So big improvement over 4 hours, but the quality is clearly not the same :(...

P.S. this should also give you an idea of how populated I want my final scene to be: each of these chairs should have a fully clothed person sitting in it, plus there would be one more fully clothed person by the board.

The wood floor looks really great!

I should also mention that I simply turned off the glass panes so that the skylight could find its way in to the room.  You can check that in the file I posted.

Obviously your setup is working but 75 fill lights seems excessive.

I am very curious to see if you can use my lighting setup to get results that are acceptable.

in general, when it comes to the final render, I crank everything to maximum and go to bed and see what happened in the morning.  I  it takes 10 hours for the final, then it takes ten hours.

I'm just weird that way and I do understand that 99% of most people are more interested in the short render.

From my personal perspective, high quality results often come from some cost in render time and my computer is a good worker.

In case you are curious how crazy I am, I rendered a 15,000 pixel wide version of the "building the ftl1" image I made and it took just a little over 4 days.

However, I'm going to have it printed 5 feet wide and I'm going to hang it in my office and a lot of people are going to see it in a very big way.  That four days of render time will pay off.

Straight out of the box the scene rendered on my machine in 15 min, so quite comparable to your results, which I was greatly surprised by.

Then I started shifting it closer to what I am aiming for: One of the first changes is adding the render passes. I need them in my workflow for post, so I never render without them. I added all the usual passes I render and re-rendered your scene with nothing else changed: 20 min. Still quite good.

Now I replaced your model with the classroom I was using before and immediately the render time shot up to over an hour (attached file - 1 hour 12 min render). And that is without the replicated lights or any other requisite items - just the bare classroom. So I am guessing the issue is in the model and, possibly, my shaders. The shaders had little influence on render times as I was changing them, but I intend to experiment more with them. I will post my results as I get them.

Quote - In case you are curious how crazy I am, I rendered a 15,000 pixel wide version of the "building the ftl1" image I made and it took just a little over 4 days.

However, I'm going to have it printed 5 feet wide and I'm going to hang it in my office and a lot of people are going to see it in a very big way.  That four days of render time will pay off.

That image was very much worth it, so I wouldn't call you crazy at all.

But in my case I simply cannot afford such render times, just becuase I need my computer during the day to do my work. Unless I can time it to coinside with an away-without-computer vacation, it's not really an option :). So, it's pretty much a once-a-year kind of deal... At most I can leave it to render overnight, but that means I need to keep my renders under 12 hours for the absolute maximum render time.

In this case I am fine with the final render taking those 12 hours, it is a very complex scene, but I need to keep it under this limit, which means that I need to build this project economizing on the render time as much as possible from the very beginning, making sure that any components I add will not slow me down too much. So now I am going to look into the model to try and figure out where the render-slow complexity is coming from.

Very interesting results.  I'm glad that you were able to reproduce my times which (hopefully) proves I'm not crazy.

I also completely understand the need to not donate your computer to rendering for days on end.  The one way I have gotten around it is to set C to render only on one head and then the computer is useable during normal usage.  That's a big waste though since it will extend times painfully.

As you can see, the model I built is extraordinarily simple (It's a total hack job).  It's what happens when you need to build something in 90 minutes.  The lighting was the focus of the exercise, not the model and that's how it worked out.

I find it very strange that the render times increased so dramatically!  I am guessing it's actually the textures and not the meshes.

hopefully, you can get what you're after and realize your final product with something that is worthy of your Carrara user level!

I am looking forward to the final result!

Thanks for the comment on the ftl1 image.  Printed huge, the micro details I put into that image will show up.  It's an insane scene.

Good call on the texture hypothesis! I just figured out that simply adding the floor texture to your model, I am also adding 12 additional minutes of render time. So the solution is to keep textures to the absolute minimum and go with solid colors whenever I can get away with it. Also - no reflective surfaces as much as possible.

In Carrara , bump maps kill GI render times. Instead, I'll exaggerate the specularity differences to replace bump. The program does seem to render normal maps faster than straight up bump maps So that is an option also.

Mark, thank you for stopping by and for your suggestion!

I have turned off everything I could find: I turned off all unneccessary render passes. I am just rendering 3D channels like distance, position and Index, Global Illumination, Glow, Background and Material Diffuse. I am not even rendering Bump, and just in case I turned Bump off in all the shaders. In the render options I am only rendering "Shadows". Nothing else! The Anti-Aliasing and lighting Quality are set at "Fast"Lighting Accuracy at 2px, so is Shadow Accuracy. Object Accuracy at 1px. Sky Light at 200% and Indirect Lighting at 100%, and I am still looking at over 30 hour render for my target resolution. Just for the room, no furniture, no characters. I just don't understand it.

I am not using textures whenever possible - nothing but black board and floor has actual image textures. Everything else is just procedural noises and turbulance mixers for colors or color gradients. The model is not super high poly either.

(The reason I want to render the room by itself is because I came up with this crazy idea of rendering the room as HDRI background using the spherical camera and then redering the characters with shadow catchers as floor and no room walls, but the HDRI instead of the modeled room for reflective light. But I can't even get a good render of the room within reasonable time....)

If you're going this route, I would render a very crude low Poly HDRI, then render a decent backdrop of the room, then render all the furniture and people separate with just the floor as a shadow catcher.

Quote - If you're going this route, I would render a very crude low Poly HDRI, then render a decent backdrop of the room, then render all the furniture and people separate with just the floor as a shadow catcher.

Yep, that's the idea.

It's not the HDRI that I am worried about, I've got it already. I don't need it to be 100% precise either - it's just to approximate the lighting. It's the backdrop that gives me grief: 30 blipping hours! And I can't seem to find a way out of it. I just don't see what else I can trim down.