In the Spine Presets I don't have any of the materials set and my project doesn't have the mentioned Straight materials.
Hmmm, that sounds weird. Could you tell us what version of Unity and spine-unity runtime you are using?
Unless I'm mistaken this is just to help automatically configure the materials and isn't strictly necessary?
Yes, the materials set in the
Auto-Import Settings in the
Spine section of
Preferences just set the materials that will be automatically assigned upon import, and can be manually modified to the correct settings. However, it is easy to make a mistake if you do this manually, so we basically advise users to modify the settings here depending on whether you are using PMA or Straights alpha textures.
In the documentation it says the if you use Linear Colour you must use Straight Alpha. Does that also mean that you need Liner Colour to use the Straight Alpha pipeline or is that optional?
Straight alpha textures can be used in both Gamma and Linear color space.