Hue rotation

cyphyr · May 11, 2021, 09:57:56 AM

Can anyone figure out how to do a hue rotation in Terragen.

I figure it could be useful to create a driver for planetary level cloud animations from a single cloud map.

For example we could get Jupiter's spot to "boil and roil" if we converted it's colours to a vector displacement and rotated them.

WAS · May 13, 2021, 12:11:21 AM

What does hue rotation mean?

You can convert RGB to masks, and mask out things and rotate them with a transform input shader. You could also use the build HSV colour to change the colour of a image (hue tint) and then multiply the colours to get RGB masks of different tones too.

cyphyr · May 13, 2021, 03:57:56 AM

This is what I mean by hue rotation. Maybe hue shift is a better term

You can achieve the same result in photoshop by moving the hue slider back and forth in Image> Adjustments>Hue/Saturation.

I don't want to physically rotate an image but rather cycle through an images colour values.

WAS · May 13, 2021, 11:27:30 AM

That would be the HSV Colour Shader

Image to Main Input, and Scalar to Hue input, and that is your slider now. I think at least. That's what I was told long time go for a hue shift. Trying it seems to have a different result.

WAS · May 13, 2021, 11:57:19 AM

Like. It does change the hue, but of all the colours... So it's just painting it all a colour from hue slider.

WAS · May 13, 2021, 12:14:09 PM

I tried making one... but it's probably no good too. It just splits RGB up, and hue shifts each channel, and rebuilds it.

cyphyr · May 13, 2021, 12:28:29 PM

Thanks for looking into it, it should be simple. I thought I had it a few years ago but I can't find the file or remember how it was done.

WAS · May 13, 2021, 12:38:06 PM

What I did can change hues of each channel, but that is cumbersome for just a hue shift, as obviously same value for each hue shift will be a result of all the same colour again.

Also a issue I've noticed with RGB selection in TG is the resulting scalars, don't actually mask all of the appropriate colour when grabbing the different channels as masks, so there is slight colour loss/bleed at the edges of channel masks. In the final mix I don't notice it having a bad effect but is very noticeable in the single channels.

Update: This wiki may explain the HSL node better and how to get the best results from it. It is meant to be RGB colour attribute picker, so I think I was on the right track.

https://en.wikipedia.org/wiki/HSL_and_HSV