[Radiance-general] replmarks and mirroring

[Lars O. Grobe]

Hi!

On may way using replmarks and instances to split down a large model, I 
found a problem that makes the use of the replmark tool quite hard. I 
use this to build the model from lots of small files, which are 
exported from CAD. The markerfiles are generated by replacing the 
external references with triangles. Works really fine.

The replmarks manpage says: "The longest side is the hypoteneuse, the 
second longest side is the x’-axis, and the third longest side 
indicates the direction of the y’-axis. Any additional sides will be 
ignored (ie. a quadrilateral may be used instead of a triangle if the 
extra side is small). The z’-axis is determined by the cross product of 
the x’ and y’ axes, and the origin is the common vertex between x’ and 
y’." This just brings one limitation - I cannot define mirroring with 
this kind of markers. In my CAD, the mirrored References give mirrored 
triangles, fine, but radiance won't mirror the instance geometry, but 
(z' as cross product of x' and y') will rotate it, so that it is upside 
down in the radiance scene.

Is there any way to circumvent this problem? It is quite bad to be 
unable to use mirroring in CAD, and makes the use of markerfiles 
difficult. I wonder why z' is not determined from the surface normal. 
Is there a reason not to use it, is it just to avoid further confusion 
(surface normals are usually where they shouldn't go;-) ?

TIA+CU Lars.
--
Lars O. Grobe
grobe at gmx.net