2008

because each final gather averages over many values of indirect illumination,
lower accuracy is sufficient.
In film production work, final gathering increasingly replaces photon mapping,
except for caustics. Without multiple-bounce effects, which are performed by
photons by default and by final gathering only if the shaders adjusts the trace
depth, tends to have far less impact on the final image than the first bounce
that final gathering supports by default. Although physical correctness is lost,
this is often sufficient for film production, and final gathering is easier to
control than photons emanating from distant light sources. However, for
accurate indoor illumination simulations and other CAD-related applications,
photon mapping is still the method of choice.
Procedures
To use an environment map as a final gather light source:
Illumination from which final gathering is derived can be provided by an
actual light source, of course, but it can also be provided by an object to which
a self-illuminated material is applied, or even an environment map. In the
latter case, follow this procedure:
1 Add a
skylight on page 4940 to the scene.
2 Do either of the following:
■ On the Skylight Parameters rollout, make sure Sky Color (the default)
is chosen, click the map button (“None”) to open the Material/Map
Browser dialog and then choose a map.
■ On the Skylight Parameters rollout, choose Use Scene Environment.
Use the Environment panel on page 6486 controls to assign an
environment map.
Thereafter, rendering with final gather enabled take the skylight map
into account when calculating final gather illumination.
TIP For extra realism, use an HDR image on page 7126 as a Bitmap map
image
on page 5633 .
Interface
Following are descriptions of all of the final gather parameters. For a helpful
tutorial that illustrates and further explains the most important of these, see
ms-its:3dsmax_t.chm::/WS73099cc142f4875514c01ac112a7acef16-7f05.htmInterior
Architecture Rendering Tutorial .
6106 | Chapter 18 Rendering