Autodesk LIGHTSCAPE, Manual

Page: 186 / 362

Radiosity Processing 11
178
Lightscape
interior accuracy. In this situation, it is important
that the walls and roof between the inside and the
outside are modeled with thickness to avoid light
leaks from the sun. For more information, see
Chapter 10, “Daylight.”
Note: Since the dynamic range of an exterior
scene is much greater than that of an interior
scene, you may need to adjust the brightness and
contrast setting of an interior/exterior solution,
depending on your view of the scene.
Setting Tolerance Parameters
Use the parameters in this group box to control the
tolerances used in various computations. These
computations allow a certain level of imprecision in
the input data and the numerical approximations
required to implement arithmetic operations on real
quantities.
Length and Initialization Minimum Area
The Length and Initialization Minimum Area
parameters are used when initiating the Preparation
model for the lighting simulation. Use the Length
parameter to specify the allowable inaccuracies
(noise) in the input data.
Note: The Length parameter is also used during
the computation of light transfer between sources
and receivers. The value appropriate for initiating
the model usually works for this task as well.
Use the Initialization Minimum Area parameter to
limit the number of initial mesh elements. This
prevents the initiation process from subdividing
mesh elements with an area smaller than the speci-
fied value. For more information, see “Elongated
Elements Are Split” on page 182.
Ray Offset
Use the Ray Offset parameter to prevent numerical
approximations from affecting the accuracy of the
shadowing computations.
Because of these approximations, the ray cast from a
surface to a source sometimes intersects an adjacent
surface very close to the origin of the ray. The Ray
Offset parameter specifies the minimum distance
from the origin of the ray before the system
considers an intersection valid.
The value of this parameter is usually slightly greater
than that of the Length parameter. Setting the value
to 0 may result in shadow artifacts. For more infor-
mation, see “Shadow Grid Size” on page 176.
Using the Process Parameters Wizard
You can use the Process Parameters wizard as an
alternative to setting the process parameters manu-
ally. The wizard considers specific aspects of your
model when setting the parameters, such as the size
of the model. For this reason, the parameters for one
model may differ from those set for another model.
Note: You can click the Back button in the Process
Parameters wizard to move to previous pages and
readjust the settings, if necessary.
To set processing parameters using the wizard:
1.
Choose Process | Parameters.
The Process Parameters dialog appears.
2.
Click the Wizard button.