Light Linking using three point lighting:
My name is Larry Neuberger and I am a professor at Alfred State
College in Alfred NY. I created these handouts to use in my classes and most of
my students found them to be helpful. I now decided to submit them to be
published on the web hoping they can help others as well.
Light linking is the art
of using multiple lights to create the illusion of one. I normally start with a
three point lighting scheme (which I will cover later) and then add lights were
needed. Linking a light to an object or objects will allow you to control what
that light affects. This sounds complex but will make more sense as we get into
it later. For this example I will use two tires I created for a car I am
working on. (Fig. 1)
Fig 1.
NOTE: IT IS IMPORTANT TO NAME ALL LIGHT AND OBJECTS BEFORE YOU START
LIGHT LINKING. You can group objects and name them or name all individual
objects. But remember to name everything.
Like I stated earlier, I am going to start with a three
point lighting scheme. This is where we use three light to initially light the
scene (key light, fill light, back light). For more information on three point
lighting, go to http://www.3drender.com.
That is an excellent source for lighting information.
To start
I added one spotlight (key Light) which will be used as my main light source
(Fig 2 - 3). This light will be
the one to illuminate everything and cast the objects shadows. Then I
positioned the light to the angle I wanted. Once the light is positioned, you
can change where it points to by pressing the show manipulator button, or T on
your keyboard. This will give you a second manipulator, which acts like a
target. Just drag this manipulator where you want the light to point to.
Fig 2. Fig 3.
After the light is positioned I would adjust it’s attributes and turn on the shadows like explained
before. Then test render to see the results. (Fig 4.)
You could also play with the decay of the light. With no decay the light lasts
forever. By using the various decays (linear, quadratic, and cubic) the light
will die out faster but create a softer light. See fig. 5 to compare no decay
with a decay turned on.
Fig 4. Fig. 5
In comparing figures 4 and
5 you can see figure five is darker but a little bit softer. Figure 5 has a
linear decay turned on with an intensity of 10. Experiment to
see which lighting fits your needs best.
By looking at the initial
render (fig. 4), you can see the backs of the objects, which are facing the
viewer, are completely black. Now as in real life, nothing is completely black
on the dark side. So we now need to link extra lights to the different objects
to backlight them. So we will now create our fill light. The fill light comes
in from the opposite side of the object, at a lower intensity that the key
light, to lighten the other side of the objects. When using three point lighting, or light linking, the main light should have
the highest intensity and cast shadows. Every other light you use should have a
lower intensity and not cast shadows. This is what I was talking about when I
said we will use multiple lights to create the illusion of one.
Create a new light and position it so it is facing the dark part of the cylinder. (Fig. 6) Then adjust it so the light is somewhat dull; I used .25 for the intensity. We may or may not have to link this light so I would render it to see if it is needed. (Fig. 7)
Fig 6 Fig. 7
The render looked nice as is so we will not link any lights
yet. You can see in figure 7 that by adding the fill light, we brightened the
opposite side of the tires a bit so we can see more detail. Now we can add the
last light in the three point lighting scheme and start light linking. The last
light is the back light. This is a light coming from behind and above the
object/s. This is mainly used just for highlights. I will now add a directional
light above and behind the tires (fig. 8). Then I will test render to see if I
like it or want to link it. (fig. 9)
NOTE: I USE MY OWN PERSONAL
PREFERENCE FOR LIGHTS. IT IS UP TO YOU TO DECIDE WHAT LIGHTS YOU WANT. YOU DO
NOT HAVE TO USE SPOT LIGHTS AND DIRECTIONAL LIGHTS LIKE I DO,
I JUST FEEL I GET A BETTER RESULT THIS WAY.
Fig 8 Fig
9
Now the three point lighting is done and you can see the
effect it has. The directional light gives some mice highlights on the top of
the tires and rims, the fill light brightens the back parts just a little, and
the key light generates the overall brightness and shadows. Now we can start
light linking. Basically, light linking will allow you to add lights and have
them affect specific objects. So now we can go through the scene and see what
areas are too dark and lighten them up. We can look at figure 10 and see what
needs to be lit.
Fig. 10
By looking at the figure above we can see the rotors and
insides of the tires are black. So we need to add a couple of lights to
brighten them a little to give it a more realistic look. I will start with the
rotor on the front tire. I will add a spot light and position it to face the
rotor (fig. 11).
Fig 11
Now we are ready to link that light to the rotor. You will
now see why naming objects is so important. To link lights we need to open the
relationship editor. Go to window >
relationship editor > light linking. You now have two options,
light-centric and object-centric. Light-centric is when you choose a light and
then select what objects it affects. Object-centric is when you select an
object and then choose what lights you want affecting it. They both do the same
thing and it is a matter of personal preference which you use. I prefer
light-centric so we can choose that (fig. 12 – 13).
Fig. 12 Fig. 13
Figure 13 illustrates the light linking window. On the left
is our lights; on the right is our objects. You can see now why naming all of
your objects is important. If all of this was not named it would be listed as
spotlight1, 2, and 3, then lofted surface 1, 2, 3, etc……. Now that everything
is named it will be easy to select everything and link our lights appropriately
in a fast efficient pace. To use the light linking window, select a light and
you will see everything it affects is highlighted on the right (fig. 14)
Fig. 14
We need to
link the rotor light to the rotor so it lights that and nothing else. So,
select the rotor light and you will see it highlights everything. The easiest
thing to do is to deselect all of the objects by clicking underneath everything
(fig 15) then select what it will be linked to (Fig. 16).
Fig. 15 Fig. 16
Now the
rotor light is linked to the rotor on the main tire and will light nothing but
that. Now we can test render to see how it looks. (Fig. 17) Now if we compare
it to the previous render (Fig. 18) we can see it adds just a little bit of
light to the bottom of the rotor.
Fig. 17 Fig. 18
Now to
illustrate light linking one more time I will add another light and link it to
the inside of the main tire. So I add a light and point it at the dark spot on
the inside of the main tire (Fig. 19), then link it to the object (Fig. 20).
Fig. 19 Fig. 20
Now we can
do a test render to see the result (fig. 21). Then compare it to before to see
the slight difference (Fig. 22).
Fig. 21 Fig. 22
You can
see that in figure 21 the inside of the tire is lit a little nicer and we
actually got an accidental reflected light on the back of the tire. Almost as
if the light is reflecting off the back tires rim.Sometimes
in Maya, the nicest results come about by accident, like in this case with the
back of the tire. It was not planned, it just happened. All I wanted was to
light the inside of the tire.
In figure
22 you can see how the back of the tire and the inside are extremely dark and
compared to figure 21 it does not look as nice.
I will
finish up with the back tire, doing the same as I did with the front, by adding
a light for the rotor and inside tire and linking them appropriately then
render it for the final product (fig. 23)
Fig. 23
Don’t be surprised
when you are done if you have a lot of lights. In my experiences you usually
will have anywhere between 3 – 5 lights for an object. In this scene I have 7
lights total of which 4 are linked to specific objects. Some people might ask
why is all this necessary? Well, if we compare the scene with linked lights and
without linked lights we can see (fig. 24 – 25)
Figure
24 has lights linked and compared to figure 25 it pops off the screen more
and looks more realistic. It shows a definitive light source and has nice
highlights and shadows. In
figure 25 there are only three lights; the key light, fill light, and back
light. Without linking lights the image looks flat and very dull. It does
not tend to pop as much as figure 24 and overall does not look as good.
Fig. 24
Fig. 25
In
conclusion, light linking is an excellent and necessary tool to use when
lighting. I would always start off with a three point lighting scheme, then add
and link lights where necessary. Remember to name everything. It is also important to be patient because this is
a very easy, but yet time consuming process. There is a lot of rendering and
tweaking involved, but if you spend the time to do this properly, the results
will be that much better.
As always,
if you have any questions, just ask.
Larry
Neuberger
607-587-4694