Good Day,

I'd like to make a case for adding Kelvin Colour Temperature to all lights in Houdini.

Since all incandescent light falls within the Kelvin colour temperature scale, and since most light sources are incandescent, it stands to reason that this extremely useful and valuable ability would be present in the Houdini lighting/shading system, especially as it is working toward physically based rendering.

I'd say easily 75% of the lighting I do could benefit from Kelvin CT as a colour selection method in Houdini. Currently, in order to find a Kelvin CT, I have my crew:

-Open Maya and add a VRay light
-Set the VRay light colour mode to Kelvin
-Enter the desired kelvin CT
-Switch the colour mode back to ‘colour"
-record the RGB and/or HSV values
-go back to Houdini and enter the rgb or hsv values for the desired CT.

Maya/VRay is quite an expensive and cumbersome Houdini plug-in just to find kelvin CT.

I have asked for this several times over the years. Not sure why such an obvious gap in the toolset has not yet been filled. Certainly most of the other relevant rendering tools have a Kelvin CT option.

If you would also like to see Kelvin CT added as a light colour option in Houdini, please add your +1 and let’s see if we can convince SideFX to throw some dev time there.

Nick

+1

Sounds reasonable to have, Arnold in Maya has Kelvin CT too. Sadly they never implemented it in Softimage for whatever reason.

Andy

What about using Light Shader?

There are also some resources how to convert KCT to XYZ or RGB (also fast conversion with some approximation)
http://www.tannerhelland.com/4435/convert-temperature-rgb-algorithm-code/ [tannerhelland.com]

(just choose the temperature and pick the values, no need for Maya/Vray)
http://academo.org/demos/colour-temperature-relationship/ [academo.org]

Well sure, there are always work-arounds. The point is workflow. It's an obvious, much needed, valuable parameter that any modern renderer claiming to be physically-based should have and that, when absent, slows a lighting TD down.

Nick

+1 but really it should be wavelengths for PBR ya

Hah. Wavelengths for physicists. Kelvin CT for artists.

MartybNz
+1 but really it should be wavelengths for PBR ya

Hopefully, someday for everything - full spectral! RGB is so 20th century.