How do I create Alpha Maps from Base Color Maps?

Table of content

1. How to create Alpha maps in Adobe Photoshop
2. How to create Alpha maps in Substance Designer

1. How to create Alpha maps in Adobe Photoshop

You can generate an Alpha map using a Base Color Map created with a ‘Generate PBR maps’ feature in Adobe Photoshop. Similar features can also be found in other software programs, allowing you to substitute them and achieve the same results.

1. When the Base Color Map has a separate background and brightness

a. To make it grayscale, select Layer -> New Adjustment Layer -> Hue/Saturation Layer and change the saturation to -100.

       (A base color map for creating an Alpha map)                  (It looks like a grayscale, but you can see the                                                                                                                                          colors when you zoom in)

b. Click Layer -> New Adjustment Layer -> Level layer to adjust the detailed contrast of the alpha map to finish it off. (Using a Curve & Brightness/Contrast Layer doesn't make much difference to the result)

                              (Before adjusting Level)                                                       (After adjusting Level)

2. When the Base Color Map has a separate background and color
a. Click Select -> Color Range to launch the Color Range window, then use the dropper to extract the background from the image. Fuzziness is an important parameter that determines the selection range. Please try multiple times to find the right value so that you can select the background well.

(You can check the selected areas in the preview window)

b. Once you've made your selections, add a Layer and fill the Layer with black. Then Select Invert (Shift + Ctrl + I) to fill the Layer with white, and you have your Alpha map.

     (Base Color Map used for creating an Alpha Map)             (Alpha map created by filling blk&wht by selection)

Summary: In Adobe Photoshop, you can create Alpha maps by adjusting the brightness and color of the base color map. It's a simple process, which is accessible to individuals of all skill levels. Please note that if your image is small or has low contrast between brightness and color, achieving an accurate Alpha map might be more challenging.

2. How to create Alpha maps in Substance Designer

You can generate an Alpha map using a Base Color Map created with a ‘Generate PBR maps’ feature in Substance Designer. Similar features can also be found in other software programs, allowing you to substitute them and achieve the same results.

1. When the Base Color Map has a separate background and brightness
a. Create a grayscale map via the Grayscale Conversion node, connect it to the Levels node, and adjust the parameters to match the detailed contrast of the Alpha map.

(Imported Base Color map → Grayscale Conversion node → Levels node)

b. You can replace the Levels node with a Curve / Histogram Scan node instead.

(You can see the same result even if you used Curve / Histogram Scan node rather than Levels node.)

2. When the Base Color Map has a separate background and color
a. Use the Color to Mask node to choose a background color and then adjust the Mask Range and Mask Softness.

(This creates a grayscale map with the background selected in white and the opposite in black)

(Color to Mask node’s options)

b. The selected background is white, so we’ll simply link it to an Invert Grayscale node to invert it.

(By inverting the black and white areas, you can create an Alpha map that will make the selected background transparent.)

Summary: In Substance Designer, you can create Alpha maps by using basic nodes. It’s a simple process which is accessible to individuals of all skill levels. Please note that if your image is too small or has low contrast between brightness and color, achieving an accurate Alpha map might be more challenging.