# Three point light

Back Light set up

The "Three-point-light" set-up is a classical, very simple scheme to achieve a scene with softer lighting. Our Spot Light is the main, or Key, Light of the scene, the one casting shadow. We will add two more lights to fake diffusion.

The next light needed is called the Back Light. It is placed behind Cornelius, see (Back Light set up). This illuminates the hidden side of our character, and allows us to separate the foreground of our picture from the background, adding an overall sense of depth. Usually the Back Light is as strong as the Key Light, if not stronger. Here we used a Lamp Light with Energy of 1 (Key and Back Light).

Key and Back Light
Fill Light set up.

The result is already far better. Finally, the third light is the Fill Light. The Fill light's aim is to light up the shadows on the front of Cornelius. We will place the Fill Light exactly at the location of the camera, with an Energy lower than the Key and Back Lights, see (Fill Light set up).

All three lights

For this example an Energy of 0.75 has been chosen (All three lights). The Fill light lights visible parts of the model which were previously in darkness with just the Key and Back light only. Reducing the power of the lights keeps the total light energy in the scene around 2.0. That amount of light is appropriate for this sized scene with these materials. As you add lights, keep an overall total even to avoid over-lighting a scene.

## Color leakage

Floor Diffuse Light set up.

The "Three-point-light" set up can be further enhanced with the addition of a fourth light, especially when a bright coloured floor is present, as in this case. If there is a bright coloured floor our eye expects the floor to diffuse part of the light all around, and some of this light impinges on the model.

To fake this effect we place a second spot exactly specular/mirrored to the Key Light with respect to the floor. This means that -- if the floor is horizontal and a z=0 as it is in our example -- and the Key light is in point (x=-5, y=-5, z=10), then the floor diffuse light is to be placed in (x=-5, y=-5, z=-10), pointing upward, see (Floor Diffuse Light set up).

The energy for this light should be lower than that of the Key Light (here it is 0.8) and its colour should match the colour of the floor (here R=0.25, G=0.5, B=1.0).

The result is shown in (Four Light set up).

Four Light set up.

Please note that we used a Spot light and not a Lamp, so it would be completely blocked by the floor (shadowed) unless we set the Spot light shadeless by pressing the appropriate button.

Indeed we could have used a Lamp but if the floor is shiny the light it sheds is more reflected than diffused. Reflected light, physically is itself a cone coming from the specular source. You can further enhance the effect by making the Spot cast shadows and by setting its ClipStart value high enough so that the plane casts no shadow, or by making it affect only its layer and placing the floor on another layer.

# Three point light - Outdoor

Sun and Hemi light for outdoor set up.

By using a Spot light as a key light the previous method is bound to indoor settings or, at best, outdoor settings at night time. This is because the Key light is at a finite distance, its rays spread and the floor is not evenly illuminated.

If we were outdoor on a clear sunny day the entire floor would be evenly lit, and shadows would be cast. To have a uniform illumination all over the floor a Sun light is needed. And if we add a Hemi light for faking the light coming from all points of the sky, as in Hemi outdoor example, we can achieve a nice outdoor light, without shadows!

The setup for the Sun Key light is:

• R=1.0,
• G=0.95,
• B=0.9,
• Energy=1.0

and the Fill/Back Light (both represented by the Hemi are setup as:

• R=0.8,
• G=0.9,
• B=1.0,
• Energy=0.4

and is shown in (Sun and Hemi light for outdoor set up) and the relevant rendering in (Sun and Hemi light for outdoor rendering).

Sun and Hemi light for outdoor rendering.

The lack of shadow makes Cornelius appear as if he were floating in space. To produce a shadow we can place either a Spot coincident with the Sun Lamp and with the same direction or enabled shadows on the Sun Lamp. Let's make this spot a Shadow Only Spot (with the appropriate button).

If Energy is lowered to 0.9 and all other settings are kept at the values used in the previous example:

• BufSize=512,
• Samples=3,
• Soft=3,
• Bias=1,
• ClipSta=5,
• ClipEnd=21

the results of which is shown in (Outdoor rendering) (center).

Outdoor rendering.

The shadow is a bit blocky seeing that Cornelius has many fine details. The BufSize is too small, and the Samples value is too low to correctly take them into account. If BufSize is raised to 2560, Samples to 6 and Bias to 3.0, you end up with the result shown in (Outdoor rendering far right). A much smoother rendering.