use Alpha channel for specular mapping


I’m using an alpha channel in photoshop for my specular map. I’ve got a uvw-map that contains metal and wood, so I want the metal to have a lot of specular and the wood none.
As a PSD file this works perfectly in Unity, but I want to create an asset to share with other people and am not sure if a PSD file is appreciated… I can’t get the file to be saved including the alpha channel as a PNG from photoshop…
Does anyone know how to do this or if it is no problem to just leave it as a PSD file for other users?

Use .png. The alpha will not be taken from the Alpha Channel, but from the Alpha in your layers.
png uses lossless compression, i think it may be the best format for unity if you don’t require editability.
Or use .tga. The alpha of the tga will be taken from what you have in the alpha channel in the psd files.

I would guess it’s normal not to put your psd files in the unity project since they will make it heavy.
Also .psd files may produce some bugs when getting read by unity.

Thanks! The TGA file worked
When you save as .tga it needed to be 32 bit though, but this probably makes sense (I’m not very technical guy)
I still need to figure out the PNG version… I tried to flatted my whole psd file to 1 layer, then add another layer underneath this one with my specular picture, but that didnt work. I only know how to use it in a way that black is 0% shiny and white 100% shiny, so maybe I need to make black transparent or something?

Anyway I’ve got a solution, so thanks again Broheim!

You can use the SuperPng plugin to save a custom alpha channel.
In Photoshop, you first create a new channel, which is called Alpha 1 by default. The data in this channel will determine the specularity (black for no specularity, white for full specularity).
The plugin adds SuperPng as a save format, which makes an extra window pop-up when saving. In this window you can select the Alpha 1 channel.

It will then save the image as a regular png file, but with the alpha channel not set as the default transparency but with the custom alpha channel you created.

If you save it as a PNG, all the transparent areas in your PS canvas will automatically form the alpha channel. As far as I know, it’s not possible to add custom alpha channels for PNG in PS (maybe there is a plugin for it?) so it doesn’t solve your problem in the case of creating specular maps. 32bit TGA is the best solution in my opinion.

thanks for the SuperPng tip! In my case, the tga´s with Alpha (1k) have 4 MB, the png´s created wirh SuperPng (1k) about 600k - and size matters…