Edit RGB channels seperatly

[eyeEmotion]

Hi,

I'm currently creating a game and for textures and such, I go into Photo and make them. I also recently discovered a technique for getting 4 maps (specular, gloss, ... , transparancy) into a single image file, by using the RGBA channels, since these maps only use the greyscale data. But I'm not able to get this done in Affinity Photo. At the moment I manage to get this is work on the complete image and on every color I use it can only be in red, green or bleu so it doesn't appear in the other channels. And only able to getting it grey in that particular channel by changing the tint in the main. This is doable with flat colors, but if a textures is complex (for example a wood-texture), this isn't that easy.
So how do I edit in my channels without affecting the others and have the same tools and adjustments at hand for working only in that channel? In Photoshop, you could do level adjustments and such, on a single channel without affecting the other channels. Your color tools would automaticly change to greyscale. But how do you do it in Affinity Photo?

Cheers

[GarryP]

I’m not sure if it’s what you want but you can use the Channels Panel to ‘switch off’ the colours you don’t want to edit.
My video shows how you can switch the Green, Blue and Alpha channels ‘off’ to erase just what’s on the Red channel.
Or you can do whatever you want to the channel, not just erase.

[eyeEmotion]

Hi,

thnx for the quick reply. I'm actually already kinda doing it that way. The problem isn't getting on the channel, it is creating something on that channel that is not effecting the other channels. Photoshop lets you draw on your channels without first having to create something and also allows for pasting an image (in greyscale) on a single channel.
When I convert shapes to pixel layers, I can draw on it with a paintbrush in that channel without affecting it. But when I create an empty new pixel layer, I can't paint in it on a specific channel, if there is nothing there. So I first have to paint something on a pixel layer with all channels on, then go to a specific channel and draw again on it, being confined to that shape.

Now I'm beginning to notice that the problems stem from that Affinity treats as much as possible as non-destructable items and that some big usability problems I've seen on here before and I'm stumbling on myself regularly come from that approach. This is where Affinity's non-destructive approach on everything is a real pain in the ***. I highly recommend them to better cater to things that require a "destructive" environment.

I'm currently getting there with what I want, but with very much frustration too much time spend on it and way too limiting in what I need to do with it.

PS: btw, how is that toolbar in the video done that way?

[GarryP]

I’m afraid I’ve reached my limit as far as channels are concerned – I generally don’t use them individually, although I should probably learn more about using them. However, someone else will probably be able to help you if they spot this thread.

As for the Toolbar, just use menu “View → Customise Tools” and then drag out the icons. I only did this as I keep forgetting what tools are available when they are concealed within drop-downs. (Too much functionality for my poor brain to keep up with.)

[Murfee]

Hi @eyeEmotion,

This video by James Ritson may help with your texture maps. https://player.vimeo.com/video/205028961/ it is a legacy tutorial that MEB hosts. 

There is no direct way to alter levels on a single channel that I am aware of, there is a roundabout long winded way though. 

Duplicate your completed texture map layer (I tend to keep the original layer and turn visibility off), add a Channel Mixer adjustment layer and make it a child layer, duplicate the layer with it's child twice. On the top layer's child channel mixer, isolate the red by turning off the green & blue channel info, do the same for the second layer but isolate the green, repeat for the third layer but isolate the blue.

Change the blend mode of the top 2 to add, this now displays the 3 layers the same as the original.

You can now add a levels or any other adjustment as a child to the isolated channel. When you are happy you can merge these 3 layers back together and you should have the result you need.

 

Yes I know its long winded and not ideal but until we get better channel editing it might help.

Edit : There is also a quicker way by adding a levels adjustment to the original layer and changing from Master to R,G or B, this can be merged. (I forgot about this one 😀)

I suppose it depends on how accurate you need to be and what your desired result is, I use channels a lot but not always in the same way.

[Murfee]

20 hours ago, eyeEmotion said:

I can't paint in it on a specific channel, if there is nothing there

If you go to the new pixel layer alpha channel and right click, now choose fill, you can now isolate each channel and paint freely.

[joosh]

Duplicate the pixel layer three times. Select one of these layers and click the little hourglass icon at the bottom of the layers window.
Scroll down and choose "Procedural Texture." A little window will pop up.

Hit the little plus icon under the "Equations" field in the window, it'll add an equation with a value of 0. Next to this equation are R, G, B and A as helpful little buttons.
Mess around with them until you get the channel you want for this layer. This can be kinda finicky, but here's some helpful formulae; R+G=B, R+B=G, and G+B=R.

Apply this methodology to all of your layers and set the blend mode of the top two channels to "Add" for the Alpha mixdown. Should be able to do something
pretty interesting with it.

Sorry it took two years for a proper answer.