I've noticed there's a lack of Pinback songs so here's a tab I found on Youtube.

This is the verse of the song, both bass and electric guitar plays this at the same time in the beginning.

G |———7———7———7———7—|———5———5———5—————|—————————————————|—————————————————|
D |—————————————————|—7———7———7———7——5|—————————————————|—————————————————|
A |—5———5———5———5———|—————————————————|—————————————————|—————————————————|
E |—————————————————|—————————————————|—————————————————|—————————————————|
    1 & 2 & 3 & 4 &   1 & 2 & 3 & 4 &   1 & 2 & 3 & 4 &   1 & 2 & 3 & 4 &

This is the chorus.

G |—————————————————|——————————————————|
D |—————————————————|——————————————————|
A |—55—55—5—88—88——8|——————————————————|
E |———————————————————|66—66—6—33—33—3—|
    1 & 2 & 3 & 4 &   1 & 2 & 3 & 4 &   
This is the second verse.
G |—————————————————|—————————————————|
D |—————————————————|—————————————————|
A |—5—55—55—————————|————7————————————|
E |—————————5—55—5——|——8——————————————|
    1 & 2 & 3 & 4 &   1 & 2 & 3 & 4 &   
If this was confusing for you, it sure was for me.
This is my guesstimation of how the song is constructed.
Verse 1 x16 (or stop whenever the song changes to the chorus)
Chorus x4
Verse 2 x9
Verse 1 x9 
Chorus  x6
Chorus (but one note of each fret) x2—3 
You end on the 5th note of the A string.
My apologies if there was an extra note missing or it doesn't make sense, but at least you know how to play the three riffs which you can formulate the song yourself with.

This was all learned on a Youtube video, so I could be wrong. If you want the direct reference, the video name is Pinback — Fortress — How to play — Simple Bass Lesson by SimpleBassLessons (Fortress SimpleBassLessons)