Direct Calculation Parameters
The parameters in this section specify the simulation behaviour
for light that is transmitted directly between a light source
and the current surface. In most cases, this will change
how shadows casted by other objects between this
source and surface will appear in images.
Set the secondary source presampling density to
D. This is the number of samples per steradian
that will be used to determine ahead of time
whether or not it is worth following shadow rays
through all the reflections and/or transmissions
associated with a secondary source path. A
value of 0 means that the full secondary source
path will always be tested for shadows if it is
tested at all.
A light
source will be subdivided until the width of
each sample area divided by the distance to the
illuminated point is below this ratio. This
assures accuracy in regions close to large area
sources at a slight computational expense. A
value of zero turns source subdivision off,
sending at most one shadow ray to each light
source.
A value of
zero samples each source at specific sample
points (see the
Direct Sampling [-ds]
option below), giving a
smoother but somewhat less accurate rendering.
A positive value causes rays to be distributed
over each source sample according to its size,
resulting in more accurate penumbras. This
option should never be greater than 1, and may
even cause problems (such as speckle) when the
value is smaller. A warning about aiming
failure will issued if frac is too large. It is
usually wise to turn off image sampling when
using direct jitter by setting
Pixel Sampling [-ps]
to 1.
Shadow testing will stop when the potential contribution of
at least the next and at most all remaining
light source samples is less than this fraction
of the accumulated value. (See the
Direct Certainty [-dc]
option below.) The remaining light source
contributions are approximated statistically.
A value of zero means that all light source samples will
be tested for shadow.
Set the number of relays for secondary sources
to this value. A value of 0 means that secondary sources
will be ignored. A value of 1 means that
sources will be made into first generation sec
ondary sources; a value of 2 means that first
generation secondary sources will also be made
into second generation secondary sources, and so on.
A value of one guarantees that the absolute accuracy of the
direct calculation will be equal to or better
than that given in the
Direct Threshold [-dt]
specification.
A value of zero only insures that all shadow lines
resulting in a contrast change greater than the
Direct Threshold [-dt]
specification will be calculated.
Navigation:
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Back to Preprocess Parameter Settings
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