Advanced Light and Materials Properties and Effects ◾ 375
Now, in Figure 15.8, we have changed the light color to a gray. We get the render seen
in Figure 15.9. is is a better balance, as we can now more easily see the variations in the
color of the horses; they have a deeper 3D appearance.
en we change the Distance to 100 and get the render in Figure 15.10. is is probably
the best render yet, as it draws out the more shadowed parts of the horses while maintain-
ing the overall contrast.
So, what have we done?
First, we probably want a gray light, so we don’t get a stark, washed out look.
What about the Distance attribute? It controls how far the eects of ambient occlusion
spread from a given point. A larger number makes things darker and a smaller number
makes them brighter. Why? Because as we increase the Distance, we are increasing the
distance over which we limit the movement of ambient light.
Just to point out the importance of choosing a color for the light in the scene, in Figure
15.11, we have replaced the Ambient Light Color by clicking on the small checkerboard at
the right of the slider and then choosing the checkerboard texture in the Hypershade. So,
parts of the ambient light have been turned to black, while others are as bright as the horses
in Figure 15.7.
GLOBAL ILLUMINATION AND FINAL GATHERING
We have looked at depth map versus raytraced shadows as well. We will review Global
Illumination and Global Illumination and Final Gathering and then introduce a couple of
new things: Caustics and Irradiance. Our goal is to consider a few dierent ways of adding
light eects to a scene. We will be using the mental ray renderer.
As a reminder, Final Gathering, which is an option you can set in the mental ray ren-
derer, adds some extra computations to the raytracer, and in doing so, lls in small dark
FIGURE 15.7 Render of AO and white light.