In this tutorial, I will show you how to make a subsurface scattering map and opacity map for your foliage project.
Texture Preparation
This was a requested tutorial
The leaf image I am using is from Ambient CG
Even though this download comes with the transparent background, I will show you how to remove the background in GIMP in case you use another leaf texture
For this tutorial, we will only be using the left-side of the image
Select the Crop tool and drag a selection around the left-side of the image
When you hit “Enter” you will now have the image we need
Right-click on the layer and select “Add Alpha Channel”
Select the Fuzzy Select tool
Click on the black background
Go to Edit > Cut and remove the background
Deselect everything by going to Select > None
Opacity Map
Right-click on the layer and duplicate it – this will be our opacity map
Hide the original layer
Select the Fuzzy Select tool and under the options, turn on everything except “draw mask”
Select the entire leaf
Right-click on the layer and add a layer mask
Leave the option on “selection” and click on “add”
Create a new layer
Select the layer mask and use CTRL + C to copy it
Select the new layer and use CTRL + V to paste the layer mask onto the layer
Anchor the floating layer
Add a new layer below the opacity map layer
Use the bucket fill tool and fill the new layer with black
Make sure only these two layers are visible
Right-click on the layer and choose “merge visible layers”
Rename the layer to “opacity” and export it as a JPG
Subsurface Scattering Map
Hide all the layers except the original leaf layer
Duplicate the leaf and hide the original one
Add a new layer beneath the duplicate layer
Use the Color Picker tool and select a midtone green from the leaf
Use the Bucket Fill tool and fill the new background layer with this green color
Make sure only these two layers are visible
Right-click on the layer and choose “merge visible layers”
Select the merged layer and go to Colors > Desaturate > Desaturate
Change the mode to “average” and click OK
Go to Colors > Levels
Adjust the color stops to your liking
Click on OK
Rename the layer to “subsurface” and export it as a JPG