Full Version: KT to TMI?
I'm used to being able to easily dial in a color temperature in Kelvins in C4D, but I don't see a way to do that in Houdini. I can take a Kelvin temperature and read the TMI values in C4D, but TMI values are far from intuitive. The current situation is that I've got a set of planes set to various Kelvins that I'm trying to set up as lights in the Stage, with a single material for the emission. As I've already discovered, I can't just use a geomprop VOP to grab the Kelvin from the @name and plug that into emissive color, because it needs to be translated. I pulled a table of Kelvin to RGB values from here [andi-siess.de], saved that as a CSV and imported it with a Table Import SOP, and I've been TRYING to create a dictionary with K as the key and the RGB vector as the value, but I haven't worked out a way to pull that off. Does anyone have any insight into how I could pull this off? Or am I better just grabbing the RGB values straight from the chart and manually applying them according to Kelvin temperature?
If you'd like to use just kelvins without luminance, you can apply them using Color Picker.
If you have Kelvins + Luminance Chart [physicallybased.info], you can make a VEX wrangle to convert Temperature + Luminance to XYZ universal color space and then to linear sRGB;
If you have Kelvins + Luminance Chart [physicallybased.info], you can make a VEX wrangle to convert Temperature + Luminance to XYZ universal color space and then to linear sRGB;
int temperature = chi("Temperature"); int luminance = chi("luminance"); vector blackbody = blackbody(temperature, luminance); vector rgb = xyztorgb(blackbody); @Cd = rgb;
Have you tried MtlX Blackbody? [www.sidefx.com]
Thanks for the suggestions, and I'm sure they'll come in handy later. What I ended up doing was naming the various objects the RGB values, then converting those names to Cd values (and dividing by 255, because I forgot that EVERYTHING is normalized in Houdini), then plugging Cd as a geompropvalue into emission color.