Aiming Failures and Geometry

radiance-general
1

Dear Group

I have a question concerning an issue that I am encountering with illum objects that were created with mkillum and the type of polygon that is used in conjunction with it. I perform quite a bit of my modeling with 3D Studio VIZ. This is more or less a "lite" version od 3D Studio Max. As many of you may already know, virtually all of the geometry no matter whether it's a sphere, cylinder, plane, etc. is composed of a multitude of triangles. To create my windows, I generally model them as a plane. When I export the scene to RADIANCE (using ConRad), all of the planes are converted to individual triangles. I have no problem using mkillum to create the illum modifiers for these polygons. The problem comes when using rpict. Once rendering of the scene begins, a bunch of "Aiming failure" error messages are generated for all of my window polygons. It doesn't matter what value for -dj I use, this error message still occurs. As an experiment, I decided to create the windows in AutoCAD. Using Desktop RADIANCE's conversion, the windows planes were translated to Radiance as four sided polygons (as opposed to three when modeled in 3D Studio). The polygons were modified as illums with mkillum and when rendering with rpict I had no "Aiming failure" error messages. My question is does anyone <coughGreg> know if Radiance has any preferences for a polygon type when the polygon is modified by an illum primative?

Thanks

Marcus

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2

Hi Marcus,

Illum's, like all light sources in Radiance, are preferred as rectangles or (at least) 4 or more sided convex shapes. Since Radiance samples a rectangle with equivalent area to the source shape, triangles are a particularly poor choice. I recommend replacing any windows you plan to use as illum's with rectangles for that reason.

-Greg

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From: "Marcus Jacobs" <[email protected]>
Date: Tue Sep 30, 2003 8:26:53 AM US/Pacific

I have a question concerning an issue that I am encountering with illum objects that were created with mkillum and the type of polygon that is used in conjunction with it. I perform quite a bit of my modeling with 3D Studio VIZ. This is more or less a "lite" version od 3D Studio Max. As many of you may already know, virtually all of the geometry no matter whether it's a sphere, cylinder, plane, etc. is composed of a multitude of triangles. To create my windows, I generally model them as a plane. When I export the scene to RADIANCE (using ConRad), all of the planes are converted to individual triangles. I have no problem using mkillum to create the illum modifiers for these polygons. The problem comes when using rpict. Once rendering of the scene begins, a bunch of "Aiming failure" error messages are generated for all of my window polygons. It doesn't matter what value for -dj I use, this error message still occurs. As an experiment, I decided to create the windows in AutoCAD. Using Desktop RADIANCE's conversion, the windows planes were translated to Radiance as four sided polygons (as opposed to three when modeled in 3D Studio). The polygons were modified as illums with mkillum and when rendering with rpict I had no "Aiming failure" error messages. My question is does anyone <coughGreg> know if Radiance has any preferences for a polygon type when the polygon is modified by an illum primative?

Thanks
Marcus

3

I perform quite a bit of my modeling
with 3D Studio VIZ.

I might be able to help you out. I model everything
with AutoDesk Revit, and then export to AutoCAD &
use RADOUT to generate my Radiance files.

(Once Revit gets better export control for 3D or
an API I'll just export from Revit directly).

I use AutoCAD to 'clean-up' my model and set things
on more specific layers, which in turn translate those
items into separately named .rad files.

Once
rendering of the scene begins, a bunch of "Aiming failure"
error messages
are generated for all of my window polygons.

I too get this error sometimes, but not with the windows
(because my windows are rectangles), I get it with the
light fixtures, because the luminescent bit of the light
fixture isn't a radiance object, but rather a bunch of
triangles or polygons exported from CAD, which cause
problems as light sources. (it makes since why when
you read the documentation on it).

What I've found to be the best way around this is to
make the luminescent part of the light fixtures into
a 'place holder' object, that I then go in and replace
with a radiance object within the .rad files.

For example, I might have a bulb within a light fixture.
Within CAD, I'll just have a point or a single triangle
marking the location of that point in space. Then, once
the model is exported to .rad files, I go in, and replace
those 'placeholders' with Radiance spheres, and then I
don't have any problems with aiming failures when that
part of the light fixture is made into a light source
for my render.

But I'm just using Radiance for rendering, not for
light analysis, so I would think that this isn't a
terribly accurate approach if you're trying to
model a fixture for testing.

Jeffrey