[TUTORIAL] How I add white streaks to hair

A repost of an answer to an ask on Tumblr. 

This can be used to make different colored strands of hair for other purposes, like having one ombre strand of hair or something. 

Please note that due to how some hairs are mapped, using this method particularly for white streaks may not work. For example, most long BG hairs have multiple parts mapped to the same place in the texture, and if I try to make a single white strand, I turn half the hair white. 

However, most short hairs, and most hairs from later packs, work with this method.

but basically I export the mesh and open it up in Blender

Then I go and remove doubles because S4S exports everything full of holes and vertices being in the same place.

Then I switch to Face Select in the toolbar in the bottom:

And then I just click anywhere in the front, where I want the white lock to be, and press Ctrl + L, which selects faces linked to the one I previously selected. In the menu on the left you can choose how Blender determines which faces to select. I select “UVs” which selects linked faces based on the UV map.

Usually when you open an S4S mesh in Blender, the interface is split in two windows: the UV map on the left, and the main window on the right. When you first select a part of the mesh, the UV map looks like this, and will export in a square image and proportioned wrong.

To fix that, find the little image icon, click it, and select any of the textures present in the list. usually the first one is the hair texture, so select that, and the UV map will be shown on top of it, proportioned right.

Next you edit your selection by putting the mouse pointer in the 3D viewport (on the right) and pressing C. which activates the lasso selection tool, and by holding the left mouse button to select, or holding down the mouse wheel to deselect faces.

Once you’re happy with the selection, you can save it to a file by going to the UVs menu in the UV map window, and selecting “Export UV layout”. This will save a PNG file with the same name as the Blender file in the same folder. You can pick a different name for your file if you want.

The next part is kind of Photoshop-specific, but if your editor supports clipping masks \ layer masks \ whatever else they may be called, you’re good to go.

I opened up the texture I exported from S4S, and opened up the UV map I exported earlier, and copypasted it onto the texture. This particular hair is a bit finicky so I had to make a separate layer and color the parts I wanted to be a different color.

Then I placed a copy of the white texture over the layer, and pressed Ctrl + G to clip the texture to the layer, creating areas of white hair. 

Aaaand that’s about it.