Color coding three parameters in one RGB image

[PabloMack]

I have seen other software packages encoding three different parameters in one color map. One is coded in Red, one in Green and one in Blue (and possibly a fouth in Alpha). As far as I can tell, Terragen does not do this but, instead, encodes only one value in the monochrome signal which is more wasteful with memory. I have been looking through the node types and am not finding the functions you would need to make use of three-or-four-channel maps. The method I am describing could be implemented if there were four nodes that might be called:

Get Red
Get Green
Get Blue
Get Alpha

What each would do is to extract the appropriate channel and return the value as a luminance value. I see there is a "Get Final Alpha" and I suppose that it might behave as I expect if working directly off a color map. I don't really understand the part about atmospheric influence on that node as described in the documentation. But the three nodes extracting their respective color channels appear to be absent.

[jo]

Hi,

In Function > Convert you can find the Red to scalar, Green to scalar and Blue to scalar nodes. They take the colour from the input and output the appropriate colour channel value as a scalar. I guess there isn't an Alpha to scalar node because TG colours don't carry alpha information with them.

Regards,

Jo

[PabloMack]

Fantastic. I wasn't looking in the right place. I guess that the alpha that is in a color map is filtered before the point at which the function can grab its value. Now I'll have to start thinking about how I can manipulate color channels in images.

Thanks Jo.

[Dune]

I use that method all the time, very handy. It would be handy to have a convert alpha to scalar as well, that would extend the use of an RGB file. But I don't really know if the file would be larger with an alpha channel than without. If I need 4 masks, I just use an extra grayscale file or even bitmap.
Making them is easy. What I usually do is make a (base) layered PS file (map on bottom, all necessary masking on top of that), then copy the layers into the appropriate channels of the final RGB masking file(s).

[PabloMack]

So far all I have used is "PhotoShop Elements" for editing stills. My understanding is that the professional version has color channel access which Elements lacks. I have an aversion to Adobe (for several reasons) so I have resisted paying the expensive price for it. I recently downloaded Gimp and am hoping that it will gain me access to color channels. I am certain that an alpha channel normally requires as much storage as any one of the three color channels, increasing storage by 1/3 in color image files. Because alpha is a property of the substrate but color is the property of the light itself, I can understand why its value does not persist as Jo pointed out.

Dune, you're a mountain of knowledge. Your technical background is serving you well.

[j meyer]

As far as I can remember there are some "Actions" available (some even free)
to make up for certain lacks of PS elements,amongst them something with/for
color channels.
I for example use one for masking layers,works really well and is legal.
Just search the web and you should find something.