Hi Andy, hi list-subscribers,
I just came across this recent message about the usability of the bsdf
material type with patch-based models of the sky including direct sun
and complex fenestration. To avoid misunderstandings, I will try a short
summary for others to comment on available options for annual
simulations with complex glazing:
1) classic radiance tools (rpict, rtrace), complemented by mkillum to
relax ambient setting.
Advantages: low noise, validated.
Disadvantages: very slow for annual simulations, no support when
non-planar specular reflective surfaces are involved.
2) rtcontrib and patch-based model.
Advantages: faster for annual simulations.
Disadvantages: noise, nice images require high (slow) -ad and cannot be
optimized using mkillum, limitations about specular non-planar
3) rtcontrib and patch-based model, bsdf.
Advantages: support for non-planar reflectors, should be slightly faster
then 2) as the fenestration system does not have to be traces internally
- did anyone compare?
Disadvantages: still high -ad settings required leading to extended
rendering times and still no way to get mkillum in, tends to
underestimate direct sun (according Andy's message).
Advantages: very fast, can also be used with non-planar specular
reflectors as bsdf data is supported.
Disadvantages: requires quite a lot of set-up work, e.g. subdivisions to
reflect external obstructions. Patches visible in the results,
fenestration geometry is not visible.
Advantages: can be used with non-planar reflectors and multi-peak
Disadvantages: unknown status (any news?), not integrated with rtcontrib
(contributions would need to be rendered manually).
So if I need a way to generate images with visible fenestration
geometry, the only reliable option would be 2), which requires very
hight settings for -ad and thud will still be rather time-consuming, if
noise is to be controlled.
On Tue, 2012-06-12 at 08:43 -0700, Andrew McNeil wrote:
Though I've found that the BSDF material doesn't work well for
daylight coefficient based annual simulations (I'm assuming dds.bash
is a dynamic daylight simulation script). Putting the solar radiance
into skypatches relies on probabilistic sampling to find patches
containing the sun, and if you don't have much direct transmission
from the direction of the sun, you aren't likely to find the sun. Not
finding the sun causes big errors.