How to create alpha/opacity maps in Photoshop?
What is an alpha/opacity texture, and what does it do?
An alpha/opacity map tells the renderer of a computer program (such as Blender, Unreal Engine, Unity, etc.) which parts of an image should be fully opaque (visible), partially transparent, or completely transparent (invisible). Let’s consider a scenario where we want a cloth on our character with ripped parts and holes. Instead of modeling the object with these features directly, which would waste polygon count, we model the object without holes/ripped parts and create a mask using an opacity/alpha map. This opacity map instructs the engine’s shader about which parts of the cloth should be completely invisible.
Tutorial
1. Open your desired image/texture in Photoshop.
2. Create a new layer and ensure that the newly created layer is on top of the image with which you want to create an opacity map.
3. Go to ‘Edit > Fill’. Ensure that your background color is set to white and the foreground color is set to black.
4. Fill the newly created layer with black color:
5. Move the black layer to the bottom.
6. Set the image’s mode to ‘Grayscale’.
7. Select the ‘Don’t Merge’ option from the upcoming menu.
Now your workflow should be looking like so:
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8. Go to ‘Adjustments > Levels’.
9. Slide the black output pin all the way to the left side.
10. Save your image.
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