RBG and Alpha channel edit workflow

[arb65912]

Hello,

This is my first post here and I hope I do not brake any rules etc.
I have searched forums but I could not really find the answer I was looking for (or I searched wrong)

I am developing aircraft for X-Plane simulator.
The newest version of it has ability to edit how metallic and shiny object is.

Without going into details, friend of mine told me that I need to paint in blue channel with colors from black through any shades of grey to white.
This different "grayness" will give in simulator different levels of surface looking like metal.

To make object more or less shiny( reflective), I am supposed to also make a map from black-any shade of grey-white color map and paste it into alpha channel.

My questions are:

1. How do I paint in blue channel?
Can I paint in different layer with different shades of grey and then just copy and paste it into blue channel?
Do R and G channels need to be visible while I m doing it?

2. How do I paint in alpha channel?
Do I also make my grey shades map in different layer and then paste it into alpha channel?

I am sure these are the basic, trivial questions but I am not even close to feel comfortable with Gimp except routine things I do all the time with UV maps.

Please explain it to me in the simplest way possible.

Thank you in advance.

Andrzej

[Ofnuts]

1) In the Channels dialog, you deselect Red and Green (but you can keep them visible), then only the B component of whatever you do will do something to the layer:

   

Above, brush stroke on a gray background using white, since only the Blue channel is selected, the Red and Green components are unchanged and the line is light blue: initially (128,128,128) painted over in (255,255,255), becomes (128,128,255).


2) You use a Layer Mask. The layer mask is just the Alpha Channel (or something which is composed with it).

[arb65912]

Thank you very much.

I will try 1 and study 2 before doing anything.

I am excited to see the results.

One question if you do not mind, where did the grey background came from?

[Blighty]

(12-08-2016, 12:36 PM)arb65912 Wrote: One question if you do not mind, where did the grey background came from?

ofnuts created a grey background to start with.
initially (128,128,128)

[arb65912]

OK, thanks!