Channel Packing Issue

[Roboko]

Hello,

In game development it is typical to 'channel pack' material data into all four channels (Red, Green, Blue, Alpha) of an image to save disk space.

Using the Spare Channels feature, I am able to control the Red/Green/Blue channels without problem, but Alpha seems to be a problem.

Whenever I use a spare channel on Alpha, it seems to also affect the data on Red/Green/Blue channels, specifically on a scale of 0-255 on each channel, every RGB value gets reset to 0 for any pixel that is fully transparent, losing the data that has been encoded into the channel.

Is there some way to prevent Affinity Photo from deleting RGB data when Loading a spare channel to Pixel Channel Alpha?

[walt.farrell]

Alpha is always transparency in the Affinity applications. I'm sure there are Feature Requests to enhance that.

[Lee_T]

Hi Roboko,

RMA (roughness/metalness/ambient occlusion), the most common channel packing method, is possible using the RGB channels but not using the alpha channel.

I've dug out one of our old videos that may help you out with your workflow:  https://player.vimeo.com/video/205028961/

Hope this helps, 

Lee

[Roboko]

In my particular case, I need to be able to encode data into the alpha channel for three textures due to the engine that I am working with

Specifically the engine uses Diffuse RGB + Emission on Alpha, Normal RGB + Glossiness on Alpha.

I guess I can't use Affinity for my projects then shame

[Old Bruce]

17 minutes ago, Roboko said:

I need to be able to encode data into the alpha channel for three textures

Three sets of information in one channel, neat trick. How is it achieved?

[Lisbon]

Hi Roboko,

7 hours ago, Roboko said:

Whenever I use a spare channel on Alpha, it seems to also affect the data on Red/Green/Blue channels, specifically on a scale of 0-255 on each channel, every RGB value gets reset to 0 for any pixel that is fully transparent, losing the data that has been encoded into the channel.

In other words, the problem only occurs in the areas where the alpha channel is fully black.

The image you will use to replace the alpha channel is it a grayscale image?
Is it ok to replace black (RGB: 0 0 0) for almost black (RGB: 1 1 1)?
This will result on an alpha of 1 (scale 0-255). Not ideal, but at the same time almost impossible to detect.

If its a grayscale and its okay to replace 0-0-0 with 1-1-1, you can try a procedural texture.
While in the layers tab, apply this procedural texture: var a=step(R,0); a/255 + (1-a)*R