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Setting VMX versus DMX options

asked 2017-04-26 17:46:07 -0600

Determinant gravatar image

updated 2017-04-26 20:21:57 -0600

I thought I knew what the difference was when setting these parameters in OS/Radiance but when examining the Ruby code I got confused. What does VMX affect versus DMX? Generally, it seems when I want to set the ambient settings I adjust them in the DMX but I thought it would be the VMX. VTDS, right? So in general to improve simulation we up the daylight matrix?

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answered 2017-04-26 21:10:11 -0600

The view matrix is the result of the ray tracing from the calculation points to the emitter (window/skylight, usually), and the daylight matrix is the result of tracing rays from the back side of the emitting surface to the sky/sun. The ambient settings matter for both, but you are right that they tend to be more aggressive for the VMX than the DMX. Some of the code may not make this seem obvious, as I recall, WRT some of the variable names I used. Silly you, trying to make sense of how this thing works by actually reading my spaghetti code (although the comments are usually good for a laugh or two). If you want to be more specific about where the confusion lies, I can try to clarify.

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No Rob, it's entirely due to my newbie-ness, not your code. It's pretty well commented (with some laughs to boot). But it's good to hear that how you explain the matrices is in line with how I thought it worked...So when Zack/anyone say/s to up the ambient parameters, ya think he/they mean/s both daylight and view?

Determinant gravatar image Determinant  ( 2017-04-28 17:25:08 -0600 )edit

From Zack's perspective, he's mainly talking about the view matrix. But if the external environment is "busy" too, you need to do your due diligence on that side of the interface too. But generally speaking, "high" parameters for a DMX are not as aggressive as those for the VMX. You can see that in OpenStudio by looking at the presets for the low- and high-quality settings.

rpg777 gravatar image rpg777  ( 2017-04-28 21:20:48 -0600 )edit

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Asked: 2017-04-26 17:46:07 -0600

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Last updated: Apr 26 '17