Autodesk LIGHTSCAPE, Руководство пользователя

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Radiosity Processing 11
170
Lightscape
You can also photometrically analyze the results of
simulations. For more information, see Chapter 12,
“Lighting Analysis.”
The lighting simulation software used in Lightscape
is based on a technology called
radiosity . Radiosity
computes the illumination of a surface from both the
light shining from a source directly toward the
surface and the indirect light reaching the surface
after being reflected (one or more times) from other
surfaces in the environment.
The radiosity processing steps include:
• Meshing
• Refinement.
Meshing
To represent variations of illumination across a
surface, Lightscape automatically breaks down the
surface into smaller pieces, called
elements . The
simulation then computes the illumination from a
light source to each corner, or
vertex, of each
element. The set of all the elements and vertices of a
surface is a
mesh .
Rather than trying to store the illumination at every
possible location on a surface, Lightscape computes
and stores the illumination only at selected sample
points—the mesh vertices. It then computes the illu-
mination across any given mesh element by
interpolating the illumination values stored at the
vertices of the element.
The number of mesh elements needed to capture the
illumination across a surface depends on the
complexity of the illumination. Small patches of
light, shadow boundaries, penumbrae, and any
other area across which the illumination changes
quickly all add to the complexity of the illumination.
The greater the amount of detail, the greater the
number of mesh vertices and elements needed to
capture it accurately.
Adaptive Meshing
To maintain as efficient a solution as possible, the
system begins processing with a coarse mesh (that is,
few elements) and automatically refines the mesh
locally where high illumination gradients are
detected. This process, called
adaptive meshing, is
controlled by a number of parameters you can vary
to provide the optimal balance between computa-
tion time, storage use, and simulation accuracy.
Components of a Radiosity Mesh
Vertex Patch Elements