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pixelweave
11-08-2007, 03:06 PM
Does anyone know where the BRDF values for the mia_materials are obtained? There are numerous references in the documentation for these values. I'm guessing it might be from a table of measurements that were made in a lab. Any clues where this data comes from? Are these just guesses?

MasterZap
11-08-2007, 04:13 PM
Does anyone know where the BRDF values for the mia_materials are obtained? There are numerous references in the documentation for these values. I'm guessing it might be from a table of measurements that were made in a lab. Any clues where this data comes from? Are these just guesses?

The ones in the manual? It's mostly guesstimates for look, not terribly "scientific". You could use more "scientific" values, but when I wrote it it was just rule-of-thumb level accuracy.

/Z

JayHoo
11-28-2007, 10:06 AM
The ones in the manual? It's mostly guesstimates for look, not terribly "scientific". You could use more "scientific" values, but when I wrote it it was just rule-of-thumb level accuracy.

/Z

I am very interested in a terrible scientific table of the values. :wip:

pixelweave
11-28-2007, 04:11 PM
I've looked at this URL (http://www.graphics.cornell.edu/online/measurements/reflectance/index.html), but I haven't had time to interpret the data (if possible). The BRDF value depends on how the empirical measurement is obtained (equipment/techniques vary), and then to what mathematical function the data is fitted to. I'm not sure what this function is in mental ray? Maybe you can only eyebal it. I started wondering about this after trying out Maxwell. Since it's main claim is to be a physically accurate renderer, I assumed that this data was somehow obtainable.

JayHoo
11-28-2007, 04:53 PM
I think it will be very hard to figure out which value is appropriate to measurements.

pixelweave
11-28-2007, 06:11 PM
Good article here as well - http://web.cs.wpi.edu/~emmanuel/courses/cs563/write_ups/zackw_measurement.html (http://web.cs.wpi.edu/%7Eemmanuel/courses/cs563/write_ups/zackw_measurement.html)

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