Alireza - Five great questions.
Rob - Five great responses.
I've done these simulations with and without spacing. There are probably
examples I've produced of both ways floating around. So I'll try to explain
why you'd want to do it one way or the other.
The basic idea is to make sure that you account for the window thickness
and edge condition once and only once in your simulation. The genBSDF
tutorial touches on the difference between a system specific BSDF, which
includes edge conditions, and an infinite layer BSDF, which has no edge
conditions. If your BSDF does not include the edge condition, then you want
your sending and receiving surfaces to be coincident, so that the edge
condition is accounted for in the view and daylight matrices. If your BSDF
does include the edge conditions, then you want a space between your
sending and receiving surfaces so that the edge condition is not duplicated
in the view and daylight matrix.
So how do you know whether you have an infinite layer BSDF or a BSDF with
edge conditions?
If your BSDF is generated by Window then it is an infinite layer, without
edge conditions.
If your BSDF is generated by genBSDF then it contains edge conditions,
unless you took care to minimize sampling of edges (see genBSDF tutorial).
If you're using proxied geometry, than your sender and receiver geometry
needs to be spaced (the thickness of the geometry) so you should make sure
that your BSDFs contain the edge effects.
For the 5-phase method, your strategy starts with what you want to do for
the direct sun coefficient matrix.
If you want to use proxied geometry than the sender and receiver must be
spaced apart and the BSDF should include edge effects specific to your
model.
If you want to use a tensor tree BSDF, then it depends on what you did to
create the BSDF. If it is a typical genBSDF tensor tree run, then edge
conditions are included in the BSDF and you should include a space between
your sending and receiving surfaces. If however you took care to create an
infinite layer BSDF (tensor tree) with genBSDF then your sender and
receiver surfaces can be coincident.
Hopefully this gives a little bit of backgroud to the whole space or no
space between sending and receiving surfaces.
Best,
Andy
···
On Sun, Jan 31, 2016 at 8:40 AM, Rob Guglielmetti < rob.guglielmetti@gmail.com> wrote:
Lots of questions, I think I can answer some of them…
>
> 1- In the tutorial, a single polygon (relative to the outline of the
glazing surface) is modeled in the scene at the exterior side of the
window. This polygon is referenced to generate the daylight matrix. A
second polygon is modeled in the scene on the interior side of the window
and it is referenced to calculate the view matrix.
>
> I was wondering if I could generate two identical co-planar polygons
where the normal vector of one polygon is looking at the interior side and
the normal vector of the other polygon looks at the exterior side to be
referenced, respectively, for the view matrix and daylight matrix
calculations? if so, would it still be necessary to model the thickness of
the walls hosting fenestration systems in the simulation scene?You could do that, just make sure that your octrees for the view and
daylight matrices only contain one the other polygon. If you have a
coincident pair of polys in the same octree, it’s up to chance which one is
hit by each ray traced. It’s already critical that every ray be counted
toward something meaningful (this is the reason for the phases in the first
place, with complex fenestration systems).> 2- What is the "proxy geometry" in the five-phase method? is the "proxy
geometry" exclusively a reference to the polygon at the interior side of
the window system that is assigned a BSDF material?
> or is the "proxy geometry" a reference to the 3D geometry of the
venetian blinds (or any other type of shading layer of the fenestration
system) in the scene?It’s the latter. That geometry serves to block the direct light, in that
phase of the workflow.>
> 3- what is the "thickness" as the first parameter in the Radiance BSDF
material type referring to? is it measured as the distance between the
daylight matrix polygon on the exterior side of the window and the view
matrix polygon at the interior side?Yes.
>
> or does "thickness" refer to the depth of the entire fenestration system
including the glazing panes and any shading layers?
>
> 4- If I model the mullions defining the edge condition of any individual
glazing pane in 3D scene, what would be the difference between using LBNL's
Window to generate a BSDF file and using genBSDF?Hmm, I don’t think there would be a difference in terms of the Radiance
BSDF and calculations.>
> 5- What would be the difference between using a BSDF file based on
Klem's division scheme with higher resolution (where each Klem's patch is
subdivided to 4 new patches) and using a tensor tree BSDF?The difference would be higher accuracy in the case of the tensor tree
BSDFs, at the expense of longer stimulation times, much larger files (both
the input and output), and longer BSDF generation times.- Rob
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