I answered in your duplicate post. But if you did it like vince suggested then the folding is done in xLights. I prefer to do the folding in the controller.
Ok I got home and set the matrix model vertical 12, 100 nodes, 4 strands per and left the controller with 12 outputs no zigzag and the output is still garbage.
Next set the model to vertical 12, 100, 1 stand per and put 4 zigzags in the controller (F16V2) and the output is still garbage.
Created a simple animation with bars going up, then left, right, etc so it would be very simple to see what was happening and when it is going left it looks mostly normal but when it goes to vertical it gets all funky.
I know this is something simple I'm missing. Thanks for any help!!!