" An optional vector that sets the hemisphere that the BSDF material faces. For materials that are symmetrical about the HBSrf plane (like non-angled venitian blinds), this can be any vector that is not perfectly normal to the HBSrf. For asymmetrical materials like angled veneitan blinds, this variable should be coordinated with the direction the HBSrfs are facing. The default is set to (0.01, 0.01, 1.00), which should hopefully not be perpendicular to any typical HBSrf."
a question come to mind:
For asymmetrical materials how excatly should the up-vector be “coordinated” with the direction of the HBsrf?
The description in HB[+] docstrings is somewhat misleading. The direction of the up-vector relates to the window-opening (aperture) to which the BSDF is mapped. With regards to your example for angled venetian blinds, as long as the up-vector is not parallel to the direction of the aperture, it should be fine. A similar question had come up on the Radiance forum a few months ago: https://discourse.radiance-online.org/t/modified-three-phase-odd-radiation-levels/4751/7
It seems that window aligns with the BSDF up-vector in one case and in one case it (obviously) doesn’t. Because you are getting almost the same value of radiation in the room as the ground plane. It’s hard to tell more without looking at the files.
[quote=“sarith, post:5, topic:4894”]
It seems that window aligns with the BSDF up-vector in one case and in one case it (obviously) doesn’t.
[/quote] The normal of window surface is parallel to Y axis while the input up-vector is either X or Z axis (not perpendicular to the window surface)
How could be aligned with together?
Thanks @sarith . Sorry for the late response.
I do not know why the skies were different in the files, but I revised them and again got very different results. The revised versions are attached hereunder:
Your calculation parameters for illuminance appear to be quite low. -aa 0.25 -ab 2 -ad 512 -ar 16 -as 128 -dc 0.25 -dj 0.0 -dp 64 -ds 0.5 -dr 0 -dt 0.5 -e error.txt -h -I -lr 4 -lw 0.05 -ss 0.0 -st 0.85
I think something like… -aa 0.05 -ab 5 -ad 2048 -ar 1024 -as 1024 -dc 0.25 -dj 0.0 -dp 64 -ds 0.5 -dr 0 -dt 0.5 -e error.txt -h -I -lr 4 -lw 0.05 -ss 0.0 -st 0.85
will likely bring both cases to convergence. If that is still not the case, I would suggest reporting this on the Radiance discourse forum. By the way, why are you focusing on the up-vector orientation specifically?