Community
Arnold General Rendering Forum
abbrechen
Suchergebnisse werden angezeigt für 
Anzeigen  nur  | Stattdessen suchen nach 
Meintest du: 

blackbody intensity

5 ANTWORTEN 5
GELÖST
Antworten
Nachricht 1 von 6
John_Smith6
541 Aufrufe, 5 Antworten

blackbody intensity

Hello,


I am currently doing some bb related math in vex and need to match (as most as possible) arnold's bb output, but cant figure out what multiplier is used to drive intensity. In my formula, once i get rgb from temp and spectrum , i do multiplication by BOLTZMANN_CONSTANT * T*T*T*T which produces huge ranges pretty quickly, but arnold outputs orders of magnitude lower values even at intensity=1 for the same temperatures. Could you elaborate on what intensity rescaler is used ?

Tags (1)
Beschriftungen (1)
5 ANTWORTEN 5
Nachricht 2 von 6
thiago.ize
als Antwort auf: John_Smith6

What if you multiply the result with (1e-6f / AI_PI)? That could explain your orders of magnitude difference?

Nachricht 3 von 6
maxtarpini
als Antwort auf: John_Smith6

IIRC,

once you get to rgb using Planck's energy distribution formula given the temperature of the emitter in degrees Kelvin (and the wavelength..)... you probably want to use the Stefan-Boltzmann constant times the fourth power of the temperature (as per Stefan's law).


Nachricht 4 von 6
John_Smith6
als Antwort auf: thiago.ize

thanks, this reduced the difference down to roughly x1.2 (in case if i normalize rgb and then multiply by all constants, and x2 if unnormalized). Does it has some physical meaning ?

Nachricht 5 von 6
John_Smith6
als Antwort auf: maxtarpini

Initially, i did exactly that -- multiply by BOLTZMANN_CONSTANT * T*T*T*T , but quickly went to millions while the arnold's output is about few hundreds (i am generating temperatures up to 13000 K)

Nachricht 6 von 6
thiago.ize
als Antwort auf: John_Smith6

The division by PI is required in order to get radiance. As for the 1e-6, I don't know why that was done. It wouldn't surprise me if there's no physical meaning and it's just what happens to give pretty results with commonly used arnold settings.

Sie finden nicht, was Sie suchen? Fragen Sie die Community oder teilen Sie Ihr Wissen mit anderen.

In Foren veröffentlichen  

Autodesk Design & Make Report