This is hopefully a tutorial covering some basics of lighting in Maya, utilising Mental Ray. I made this tutorial for someone in a forum and tried to replicate their scene to better show them how to control their lighting. So while I wish I had some more detailed models in there to demonstrate with, such as the head, I used what I could find that was shaped most like the stuff in their scene, rather than what looked best. I don't consider myself great at lighting or anything, but I noticed a lot of people seemed to have issues with artefacts in their shadows, or lighting set ups that make it looks like it has artefacts, or they can't soften their shadows, so I figured I would try to help out. There's probably some better ways to do some of this stuff, but this is what I have to offer, and hopefully I'm not providing any incorrect information.
I will start off on the concept of 3-point lighting, as I understand it. The three light points are typically referred to as Key, Fill and Back. We will cover this all again when we start lighting, but first we have an overview so we are working with the same mind set.
1. Your key light is your main light source. Sun, lights above, spot lights, etc. This is your main light source. Often it seems like people aren't sure where to put this light and will toss a light wherever and often in places that make no sense. In a case like this you may want to tell yourself a bit of a story if you're trying to get it to blend into a scene nicely, and figure out where this light would be coming from in the scene. It's possible it's just lighting you set up for a beauty shot there, but try to think of it like how you might light it in real life. But anyway, the key light is mainly where your light is coming from. Pick an angle that defines the features of your model well, if you can. Sometimes you pick realism over design, but I suggest that whenever you can, since artists are often trying to show off their work, light at angles that are going to cast shadows and catch highlights in a way that best defines the features of whatever the focus of the scene is.
2. Your fill light is off to the side and is again used to help display the details of the model, rather than hiding it in hard shadows. It simulates the way that light typically diffuses across an object. In real life light diffuses across a surface and we have bounced light, etc. So sometimes, in lighting a shot, we're helping to accentuate that, which is generally what I use a fill light for.
3. Your back light is used to break the image up from the background. A lot of people tell you that your key light is your brightest light source. Often I have my backlight just as bright, if not brighter, for my back light (but not always). The idea is to get just that bit of rim light on the back to break up the model from the dark or similar spots on the background.
Now, while it's called 3-point lighting, there is often a misconception that this means only 3 lights in the scene. Nothing could be farther from the truth! 3 points refers to 3 bulletin points. It's not the light itself that is important, but the concept that the bulletin point is trying to execute. A better way to think of the three points of lighting is like this:
- Set up lights for your main source(s) of light
- Set up lights to diffuse the light from your key lights across the surface of your models
- Set up back lights that help break up the model from the background and give them added depth
So even though it's called 3-point lighting, it's very rare that we ever use only 3 lights. In this tutorial, as we go, we will have other light sources from a background image that isn't accounted for in the lighting of the render that we will have to emulate. There will be a bounce light from a floor that isn't there, so we will have to add it ourselves. So these are all lights I will add after my 3-point lighting (though, depending on the scene, they could just as easily be part of the 3-point lighting too. Really, any light you add tends to add to one of the points!).
I remade this scene with an old, ugly head that looked similar in shape to the head I was comparing when I made this tutorial, and I remade the pedestal. The background is an image plane attached to the camera. Whilst not the prettiest thing, it's enough to catch light well enough to demonstrate the process.
When I light a scene, I usually start with a white Lambert on everything. The reason for this is because I want to see exactly what the light is doing, how it's casting shadows, etc. I use white so I can see what areas get washed out easily. If I have textures on, they can confuse me as to what is shadow and what is texture. You can throw on a bump map or displacement map if you want to get that detail, but I usually wait till later when I do, because they add render time. You can easily get through this tutorial before needing to add bump or displacement, and at the end of this tutorial I would still continue to tweak my lighting as I work.(Fig.01)
First, I will use a spot light, and then soften up the fall off on it. I use the manipulator tool to easily set up its placement and direction.(Fig.02)
I then hit that little blue dial button by the light two times until I get to this tool, which lets me adjust the Cone Angle and then click it once again to adjust the Penumbra Angle of the light ( I could do this from the attribute editor too, but I prefer the visual method). I believe the first one is where the light fall off ends from the center of the light and the second is where that solid center of light ends and starts to fall off. ( Fig.03)
Next I open up the attribute editor for the light and go to the Shadows tab. I turn on Use Ray Trace Shadows and set the light radius to 10, and both shadow rays and depth limit to 3.
Really, in this case, I probably don't need depth limit because we don't have anything transparent. Depth limit is how many times a ray will pass though a transparent object and refract. Something like glass, it could theoretically bounce 100s if not thousands of times, so we limit it to just three bounces before it stops. Shadow rays if I recall correctly is how many samples Mental Ray takes. A lower shadow ray setting will be grainy and a higher shadow ray limit will be softer and smoother. For now, keep it low while you're testing but for your final render you may need to turn it up. Keep in mind that the higher the setting the longer the render time.(Fig.04)
We're going to use final gather to render this. The difference in ray tracing from final gather is that ray tracing the rays come from the camera and go to the object. Final Gather the rays come from the light and go to the camera. Actually, here's what the help menu describes it at, which explains it better than I probably will:
With Final Gather, rays are first cast from the light (rather than from the camera, as with simple ray tracing). When a ray strikes an object, a series of secondary rays are diverted at random angles to calculate the light energy contribution from surrounding objects, which is then evaluated during the ray tracing process to add the effect of the bounced light. This basically turns every object into a light source so each object in a scene influences the color of its surroundings as in the real world.
So next, we'll go turn on our render settings to use Mental Ray rather than Maya software. I'm going to set it to Preview and Final gather. This will give us a quick render time to see how our lighting is going. Remember this part later, because come your final render, you will want to change this at least to Production quality. (Fig.05)