Painting Channels

[bnienburg]

Clearly I'm just missing some simple setting here.  In PS, I can freely paint on any individual color channel.  When i do this in photo however, the paint tool just seems inactive, or tied to the existing 'mask'.  So I'm unable to paint white, anywhere that doesn't already have color information (or presumably an active alpha info).

 

This is no good, as I'm using each separate channel for different uses in game shaders (including alpha) so i need to be able to manipulate the red channel, for example, independent of alpha (which will also be used).  Is there some 'ignore alpha mask'
If I fill the alpha completely white, and put the image data I need on a 'spare channel' this technically acts in the way I need... but production pipeline wise, as I'm editing hundreds of these at a time, duplicating the channel, filling it with white, and then later loading the spare channel back to the alpha, so I can save and test, is a real hassle, and costing a good deal of time.

[GarryP]

I’m not an expert in this area so I can’t give much of an explanation but I notice that, in your first example, your canvas is black while the thumbnail of the pixel layer just shows the Layers Panel background colour. That might have something to do with what’s happening.
Also, we can’t see all of your Context Toolbar. If you have the Blend Mode of the Brush (not the layer) set to – for example – Darken, then painting in white on a black background probably won’t do anything, in this case.
I’ll let the experts come in with better advice but I thought I would point these things out in case they helped.

[carl123]

12 hours ago, bnienburg said:

Is there some 'ignore alpha mask'

Try Protect Alpha on the context toolbar for the brush, which you cant see as your screen is not wide enough