Hello Seth!
For Vertex Streams you are only allowed to use from TEXCOORD0 to TEXCOORD3 and each TEXCOORD has 4 channels available, and in the
Custom Vertex Streams, your TEXCOORD1.xyzw would be the UV Set 2, which correspond to UV Sets 1 to 4, so TEXCOORD0 would be UV Set 1, TEXCOORD1 would be UV Set 2, and so on.
Do note that Unity, UI-wise, will warn you if you start using more than 4 Vertex Streams, so that you can re-arrange your
data to fit on those available. This is subject to being changed on Unity's side in the future.
To access this
data, you may use the
Vertex TexCoord node or the
Texture Coordinates, but we recommend that you use the Vertex TexCoord as it provides the texture coordinates directly from vertex
data without any further calculations.
You'll need to set the Coordinates Size and indicate the UV Channel to use according to the
Custom Vertex Stream
data you want to access. The Coordinates Size parameter allows you to read more packed
data from vertex coordinates, with sizes of Float2 to Float4, and the UV Channel, as explained above, accesses TEXCOORD0 to TEXCOORD3 as UV1 to UV4.
( Note: The Vertex TexCoord node currently display UV0 to UV3 but this is going to be changed for consistency purposes )Please let me know if this helps, thanks!