Graphics Programs Reference
In-Depth Information
Two important functions that mental
ray brings to the Maya table are caustics
and global illumination (GI).
Caustics
is
the scattering of light reflections off and
through semitransparent objects, such as
the light that shines on the ceiling of an
indoor pool or the sunshine at the bottom
of an outdoor pool.
Global illumination
is
the effect of light reflected from one object
to another. For example, if you place col-
ored spheres inside a gray box and shine
a light into the box, the walls and floor of
that box pick up the color of the spheres.
The light from the spheres reflects onto
the walls and tints them with the spheres'
color. Furthermore, the light from the floor of the box bounces and helps illuminate the
underside of the balls.
For example, Figure 10.37 shows a scene file that has a dozen or so glass spheres inside
an enclosed box. The box has four holes in the top, and two spotlights with shadows
turned on are positioned outside the box,
shining in through the holes. Figure 10.37
shows a typical software render. The
spheres under the holes are visible, and the
rest of the box is in shadow.
However, when rendering through men-
tal ray for Maya (see Figure 10.38), the light
that enters the box bounces around the
scene and illuminates the other spheres.
The color of the spheres also colors the
area immediately around them due to GI.
Additionally, the light shines through the
semitransparent spheres and casts caustic
highlights on the floor. (You can see the
full effect in the color section of this topic.)
Figure 10.37
The Maya Software
render of the box of
spheres scene
Figure 10.38
The mental ray
for Maya render
of the scene in
Figure 10.37
Global Illumination: A downloadable PDF Exercise
Global illumination and caustics are both advanced lighting effects and won't be cov-
ered in this topic. However, a short GI exercise from a previous version of this topic is
