Cineversity

I’m very intrigued with the way you’re using Omni lights to fake GI.  Especially interesting was the way you keyframed the color of the lights over time to give the impression of movement, etc.

Just wondering—how do you place the lights, like the floor light for instance?  Is it just a light placed low in the center of the scene, or is it travelling with JET as he moves?  I’m sure a lot of it is by eye, but is there an intensity you use for a jumping off point when placing the lights?  Also, I assume the light from the building goes near the building, etc.  Finally, are you using inverse square or inverse square clamped falloff, or something else?

I’m tearing through these tutorials, so I’m happy you have a release schedule with more coming soon!

Best,
Biagio

Hey Biagio,

Thanks for your interest.

Gi is certainly a great option to have, but quite honestly, I’m too impatient most of the time to use it. On the other hand, reflective objects have not really an advantage from the direct light that hits them, certainly not a lot from GI (except Caustics as by-product), they live of course from reflections. Nothing is 100% reflective and there comes the light source in the game. The sun is a huge light source creates out of nearly anything a light source, hence the idea of GI or Image based lighting. It can be of an advantage to even take the sun out of an HDRI and replace it with a real light source in C4D. If you go for example in the material editor, the different render methods Phong or Blinn, Oren Nayar are not available in pure GI scenes (!) but they would define so much the reality appearance. There comes the light object into the game and the GI is even lower again in its potential. On the other hand, teh few light source to fake reflected light from the context is easily set up and takes nearly no render time. The best is, it is always flicker free. So, I’m not a big GI user, I paint with light (see Cinematography series)

The question of “Inverse Square”. I have an episode about that in an series that is on the publishing list of “JET”. I see sometimes people explaining exactly how much intensity a light should have, and that inverse square is the correct “thing to do”, only to see then that they pull on the “target” of the light and increase dramatically the intensity, after all was set up “correctly”. Yes Inverse Square is the correct thing to do for any non parallel light —will say spreading light. Focused light becomes even brighter, until it surpasses its focus point.
The sun is a spreading light in the universe, but here on Earth it is a parallel light. Even if we go like a bean-counter to work and say it is not parallel, we need to apply the Inverse Square rule. Lets have a look: The distance from sun to earth is one unit. After another of this unit, the light would be less according to the inverse square rule. Well put that distance sun-Earth in relation to anything here on earth and the formula shows no real effect.
For building reflections that huge, I have the impression that the overall light (haze, dust, etc) is not as simple as that. If a building wall reflects the light even to a small object the overall illumination is a little bit different than a point light.

I hope I got the question with the light and movement right. Normally light-sources doesn’t travel, so I place them where I need them. I’m not in the business of scientific simulations here (sorry), I’m a film maker and what ever supports my story is right. E.g., Nothing is real in a studio. In the days of SD definition (remember these days?) the speakers desks were painted sloppily, as the cameras couldn’t pick it up anyway. With 6K RED around the corner that game will change even more than with HD, but my point is, what ever delivers the picture and the story—is the way to go.

We have a lot of unconscious observations, and “we” feel if something is right or wrong, there we need to observe as artists. But on the end, if we introduce a certain style and stick with it, if done well, the audience goes with it. Some “wannabe-critics” won’t, but who cares about them? It’s all about delivering a good time :o) Observation in reality is as important as the use of our tools.

The next piles of tutorials are more practical, the first three series (Cinematography, Integration, JET making off were my main work), but the current mammoth series is from start to finish an expression of my affinity for our craft here. :o)

All the best

Sassi

Thanks for your reply.  I’m with you—I love to “cheat” and anything to make something look better faster is well worth learning.  Just one last thing…do you put the floor light right in the center of the scene to start, and tweak from there?  I’m really interested in doing that.

Thanks!
Biagio

Hi Biagio,

I checked some files and the best I can say, I adapt to each scene. This is the most precise I can say if a general answer is needed.

While I shot an image for a scene like this one, I take normally some context snapshots (call it “Set Survey” if you like), or if that is not taken, check out Google Maps Satellite for reference. This helps to get a sense of the situation and the “materials” as well the quantity/quality of them.

In short, if you have an area with grass, a green/yellowish light is preferable. Linear falloff is my selection for JET most of the time for these secondary lights (I checked). I assume that the sun on a green patch results in millions of little lights, so the further the object goes, so my private theory, the more of these little lights might affect a small object.  I’m not really into the inverse square here, as we have a lot of inverse square lights working together, and the more distance to an object the more working on it. Which has a little bit of an parallel light in it, ... a tiny bit

However, the larger an area is the more likely I use many light sources for it. Two important things needs to be known, in fact standard things, so I don’t stress them too much, but will do in a series about light.

First - for any fill light, consider carefully if a specular highlight is appropriate. Secondly, and this is something I’m always baffled when I get a scene—The Light>>Detail>>Contrast slider is on default. Everyone will tell you that a small light source will result in a harsh light, a large source will remain soft, except you move it away. But funnily enough, that is what the Contrast Parameter is for, to fake exactly this. With this slider you can simulate a softer light (or the opposite of course) and no hazzle with rendering area lights. In that way, if the specular is not giving away the position of the light source, a small negative contrast allows for a soft-box effect.
This is then of-course the light that we believe more as an GI fake than a point or spot light with all its characteristics.

You use the Diffuse channel and that is a nice way to get more reality into the image. No average material is like the default setting, it is most of the time darker. Having set up the material to a more natural diffusion (it is after all a fake) allows for a strong Main light. (I avoid here the “Hollywood Standard 3 light” set up terms, as that is only (!) an starting point and bad teaching about it has obviously ruined more movies than filming with practical light in the first place ;o)

As the set up and test render of these lights are more or less fast, it is easy to find the right positions. If you go then with Multi-Pass to work, you have each light source in “real-time” in Ae, NUKE or Flame, etc.

I hope that answer the questions, if not, please ask :o) On the end the situation requests a solution, not a “one size fits all”—hence my comment on the three point light ;o)

All the best

Sassi

Extremely helpful, Dr. Sassi!  I didn’t even know the contrast slider existed!  It might be my new favorite “feature” I didn’t realize existed.  I just tried turing the contrast down in my test scene and was thrilled to see some of the harshness of the normal omni lights taper off.

As you know, when trying to get these things done on a schedule, GI rendering is not usually an option.  Watching the way you work with omni lights to create a “fake Gi”—or better said—make t he scene more “real” is exciting and I’m looking forward to incorporating it into my workflow.

Thanks again,
Biagio

Thank you Biagio for the feedback.

Yes GI is for many things a wonderful and great option, but for animations on a tight deadline not so much. I always appreciate the “idea” of the indirect light that a short GI rendering can give me about a scene. It is a great tool to create individual reference renderings. Besides that, baking Gi into secondary objects (which will not be affected by animations) might help as well.

I think 12 year or so ago, someone created a plug-in that placed lights on surfaces and turned them into GI fakes lights (color and intensity)—it is long gone, but that is exactly what happens, every object becomes a light source.

Have a nice Sunday

Sassi