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Raydirect User Manual
How to use the Raydirect Plug-In
Raydirect applies its functionality to rectangular polygons within
the object file it is assigned to. Typically, those polygons will be
positioned near the glass surface in a window, with a small distance
to the glass, accounting for the physical thickness of the system.
The surface normal must
point to the inside of the building, and the polygons should
not intersect with any other elements. Geometry other than
rectangular polygons in the same object file will get passed
through without change, or may cause an error in some cases.
When using Raydirect in a simulation, it is important to apply
the following changes to the Rayfront simulation parameters
:
Switch the dialog to "Extended Options" mode using the button
near the bottom of the dialog.
Set the Direct Sampling Ratio parameter (-ds) to a value above
zero. In most cases, a value of 1 will give reasonable results. If there
are geometry elements very close to the polygon treated by Raydirect,
then a value higher than 1 may be necessary, if the polygon has a
large distance to all surfaces illuminated by it then a value below
1 will be good enough.
The purpose of this parameter is to subdivide the virtual light source
when illuminating surfaces located very closely to it, in order to better
approximate the fact that we're trying to simulate an area light source.
Set the Direct Jittering parameter (-dj) to a high value,
close to 1. In some cases, you will find warnings in the
simulation log about "aiming failures" after doing so. If there are
many such warnings, then reduce the parameter value again,
until there are only occasional warnings. Those warnings will
not have any negative influence on the results of Raydirect itself,
but may cause a slight underestimation of the contribution of the
sun (and some other light sources) to the rest of the simulation.
The purpose of this setting is to distribute the rays sent
to the virtual light source over the full surface of its
area, which will give more realistic results.
Set the Pixel Sampling parameter (-ps) to a small value,
ideally to zero. The direct jittering parameter above doesn't
play well with pixel sampling. Pixel sampling works best in scenes
where there are no small small features of varying brighness, and
no speckled areas due to random sampling. Direct jittering does apply
such random sampling, wher the final result must be interpolated
between several fully computed pixels. In contrast to that, pixel
sampling interpolates values in place of computing them, which is
a conflicting concept. A pixel sampling value greater than two
together with direct jittering will result in visual artifacts in
the picture, such as horizontal stripes.
At first, the light emitted from the redirection system will cause
a speckled appearance of the surfaces it illuminates. To remove this
effect, it is necessary to run the simulation with high quality settings
(or possibly medium). This will render a raw image two or three times
larger than the target size, which is then filtered down. The filtering
process will eliminate the speckles through interpolation.
Please also check the information about
Caveats and Pitfalls,
in order to avoid misunderstandings that might invalidate your results.
Precompute Object Surfaces as Light Redirection Elements
This option in the object properties dialog will activate
the Raydirect plug-in for Rayfront, and is only available when
that module is installed.
Redirection Element Type:
Select the system type here. Each product found in the
installed data files will have an
entry in this list.
Redirection Element:
If the selected element type can be installed in different
positions, or is moveable, then you can select the element
with the right position here. Usually, this means that the
profiles can be rotated around their lenght axis. In that
case, each position will be speficied with an angle, where
zero means a horizontal position, a positive value means
a rotation towards the outside, and a negative value means a
rotation towards the room.
Generate # Output Patches:
When set to a number higher than one, then this option
will generate several ouput surfaces for the virtual
light sources created by Raydirect. This may be useful for
very tall panes, but shouldn't normally be necessary.
The direction of the subdivision is determined by the sequence
of the vertices of the polygon. It will be split in parallel
to the edge between the first and the second vertex.
Rotate Profiles from Horizontal:
Most systems will get installed in a position so that the
profile direction is horizontal. In some cases, however, especially
for roof windows, it is necessary to rotate the arrangement of the
profile orientation within the plane of the window. This parameter
configures the rotation angle away from the horizontal direction, and
is given in degrees looking from the room. When the window itself is
exactly horizontal, then the zero position is so that the profiles are
alligned with the positive X axis.
Scale Visible Profiles by:
Besides the virtual light source responsible for the distribution
of the light coming from the redirection system, Rayfront also inserts
geometry visually representing the system in the visualization.
If you want that representation to be more or less visible than
it would normally appear, then you can scale it by entering
a value other than 1.0 for this parameter,
Compute Direct Component
When this option is selected, then Raydirect will take the
direct sunlight into account for the simulation.
The procedure that determines the light received by the
system from the sun checks whether it actually sees
the sun, and how much of that light is filtered
by transparent elements such as window panes. This visibility
calculation operates from the center of the polygon.
Compute Diffuse Component
When this option is selected, then Raydirect will take the
diffuse light from the sky into account for the simulation.
The procedure that determines the light transmitted by the
system from the diffuse sky determines the actually visible
portions of the sky, taking into account all obstructing
elements between the window and the sky. This visibility
calculation operates from the center of the polygon.
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