Generating view matrices for multiple glazing apertures in Radiance?

I want to generate view matrices for each of the 6 separate windows in a room with rfluxmtx. I wonder what is the best practice to do so?

Should I put the window I'm interested in in a "GlazingVmtx.rad" file, run someting like

rfluxmtx -v -I+ -ab 4 -ad 5000 -lw 0.0002 -n 16 -y 100 - objects/GlazingVmtx.rad -i octrees/room3ph.oct < points.txt > matrices/vmtx/v.mtx

, and include the information of other windows in the octree file?

Or, can I put the information of all the windows in one rad file (for example, GlazingVmtx.rad), but only set the window I am interested in as a glow type?

Thanks in advance.

101

JChen1234

asked 2021-01-04 18:46:13 -0500

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__AmirRoth__

updated 2021-04-05 10:46:12 -0500

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I found that Section 7.4 of Daylighting Simulations with Radiance using Matrix-based Methods gave a good example of what should be done. In general, the walls of the room are put in the octree file. The different windows are put into separate rad files to generate the view matrices separately.

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JChen1234

answered 2021-01-07 12:03:58 -0500

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While it is true that you can only have one sender object per rfluxmtx calculation, you can specify as many "receiver" objects as you like; in this case, all of the windows in a given room. The sender in this case is replaced by your selection of points, as is normal for a view matrix calculation. To include multiple receivers, you need to specify the output file ahead of each window's polygon using the

#@rfluxmtx o=output.mtx

variable as described in the man page https://radiance-online.org/learning/...

The view matrix calculation will also be more efficient if you can avoid running it separately for each window in this way.

While you did not ask, you do need to run rfluxmtx once per elevation (i.e., direction) to calculate the external "daylight" matrices connecting the building exterior to the sky, since the sky (+ground) is in this case the only receiver. Normally, this means running rfluxmtx once per window. A shortcut is possible when there are few nearby obstructions outside the building, and the windows all lie in a plane that you can assemble as a single "source" for that elevation, even though they may be physically separated by mullions or wall sections. Again, it will be more efficient to combine calculations in this way, but it is not required by the method.

The tutorial recommended by JChen remains the authoritative source.

Best, -Greg