The 4-tile spritesheet for sectopods or reapers is divided into:
4 tile-sprites (obviously), top, bottom, left and right (think user-wise, not unit-wise)
- each having 8 facings
- each having 5 animation frames (including stationary)
for a total 4*8*5 = 160 frames in the sprite sheet
The sprite sheet starts with all the facings for the stationary sprite (0-7 for top tile-sprite, 8-15 for the right, 16-23 for the left, 24-32 for bottom), then it starts over with 32-47 being animation for facing 1 (NE, as with the soldier sprite), 4 frames for the top tile-sprite, then 4 for the right, left and bottom each, for a total of 16. This pattern repeats with all the 7 remaining facings.
For easy reference, take a look at my ripped and reworked Triscene spritesheet (under Sprites/TRD_6 in the Piratez mod), they didn't give a damn about occlusion so it's much easier to understand than studying Sectopod or Reaper spritesheets. Just don't look at the original TFTD Triscene if you have it, TFTD uses a different frame order.
