genBSDF with blinds only?

Let's say I want to make a BSDF for a venetian blind, that I could attach to a polygon that is *not* a window, but rather a proxy surface (because I do).

genBSDF still needs a uniform polygon to sample from, right? But I want this polygon to be completely invisible to the simulation, it's just representing an area from which to sample. Could I use antimatter in this case? In other words my input geometry would just be the blind slats (all in the -z), with a single polygon to represent the interface, which would serve as the area for the sampling origins as well. It is this polygon that would be made of antimatter. The point is to make a BSDF that just represents the scatter of light passing through the blinds. It seems that in all the examples I see out there, the input geometry describes an entire window system, with glazing and frames and everything. My goal is to make a general BSDF for the blinds only, which could be inserted into any model (either as a BSDF material, or as a T matrix), applying it to a proxy polygon just inboard of the window/IGU.

Help.

Rob.

Hi Rob,

The trick is to use the "-dim" option of genBSDF to sample an interior region of the blinds, thus avoiding the edge condition and creating a BSDF that you can apply generically. Andy McNeil has an example of this in the genBSDF tutorial he is writing. I will send you a draft of it off-list, as he's not quite done editing it.

In general, genBSDF always creates a virtual surface for sampling, and when you apply it to a surface for rendering, it behaves as a proxy for the actual geometry. You can of course include real geometry if you like by giving the BSDF primitive a thickness, and this is described in my presentation from a few workshops back:

  http://www.radiance-online.org/community/workshops/2011-berkeley-ca/presentations/day1/GW2_New_BSDF.pdf

Cheers,
-Greg

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From: "Guglielmetti, Robert" <[email protected]>
Subject: [Radiance-general] genBSDF with blinds only?
Date: July 10, 2015 9:37:58 AM PDT

Let's say I want to make a BSDF for a venetian blind, that I could attach to a polygon that is *not* a window, but rather a proxy surface (because I do).

genBSDF still needs a uniform polygon to sample from, right? But I want this polygon to be completely invisible to the simulation, it's just representing an area from which to sample. Could I use antimatter in this case? In other words my input geometry would just be the blind slats (all in the -z), with a single polygon to represent the interface, which would serve as the area for the sampling origins as well. It is this polygon that would be made of antimatter. The point is to make a BSDF that just represents the scatter of light passing through the blinds. It seems that in all the examples I see out there, the input geometry describes an entire window system, with glazing and frames and everything. My goal is to make a general BSDF for the blinds only, which could be inserted into any model (either as a BSDF material, or as a T matrix), applying it to a proxy polygon just inboard of the window/IGU.

Help.

Rob.