Autodesk LIGHTSCAPE, Manual

Page: 190 / 362

Radiosity Processing 11
182
Lightscape
Double-Sided Surfaces Are Converted
Double-sided surfaces are converted to two separate
surfaces, oriented in opposite directions—each
corresponding to one side of the original surface.
The system stores the illumination in a radiosity
mesh attached to the surface itself. Because double-
sided surfaces are overlapping, they are automati-
cally set to be nonreflecting. Therefore, you should
use double-sided surfaces only where strictly
necessary.
Surfaces Are Grouped
The resulting surfaces are grouped into larger
surfaces. To be part of the same larger surface, input
surfaces must be on the same layer, share the same
material and surface properties, be coplanar, and
form a connected surface.
A surface is considered to lie in a given plane if all of
its corners are within Length Tolerance distance
from the plane. For more information, see “Length
and Initialization Minimum Area” on page 178.
Lightscape eliminates T-vertices in the surfaces
being grouped. A T-vertex occurs when the vertex
from one surface meets an edge from an adjacent
surface. This situation can lead to a discontinuity in
the radiosity solution, so Lightscape adds a vertex to
the edge at the point of intersection.
Radiosity Mesh Is Created
The system creates an initial radiosity mesh that has
an illumination value of 0 for each resulting surface.
It connects the vertices of the input surfaces to form
triangular and convex quadrilateral mesh elements.
Elongated Elements Are Split
Long, thin elements may be split into smaller
elements. Meshes made of well-shaped elements,
such as an equilateral triangle or a square, are more
efficient and less likely to produce visual artifacts.
To limit the number of mesh elements, you can use
the Initialization Minimum Area parameter on the
Process Parameters dialog. This prevents the initia-
tion process from splitting mesh elements with an
area smaller than the specified value. For more
information, see “Length and Initialization
Minimum Area” on page 178.
Processing the Radiosity
Solution
Once the model is initiated, process the solution to
compute the direct and indirect lighting in the
model.
To process a radiosity solution:
1.
Set the processing parameters. For information,
see “Setting the Processing Parameters” on page 172.
2.
Set the surface processing parameters. For infor-
mation, see “Setting the Surface Processing Parame-
ters” on page 179.
3.
Initiate the model. For information, see “Initiat-
ing the Model” on page 181.
4.
Choose Process | Go or click the Go button .
Note: To calculate a solution with only direct
lighting contributions (and no reflected light),
choose Process | Direct Only instead.
Surfaces before initiation Surfaces after initiation
T-vertex