MASH orient node up vector problem

[Anonymous]

I'm hoping to use the the flight node in MASH to simulate fish shoaling using instances but right now I'm running into a problem keeping my fish upright because the orient node doesn't seem to offer world space Up vector control. The attribute labelled "Up vector" in the orient node is actually an aim axis vector. So, for example, if I try to get the fish to swim around in a circle they flip upside down in some orientations and then flip back upright again as they continue around the circle.

Is there any way to add up vector control to the instances in conjunction with the orient node?

An alternative approach I've explored is to avoid using flight at all but instead use the curve node with an aim curve to control the up vectors then adding a noise node to break up the motion of the shoal. The drawback of this approach is that there's no collision detection between the instances.

Cheers for any help,

[Anonymous · Accepted solution]

So the solution to the orient on velocity problem is simply to align the master fish vertically so that its belly faces along the world z-axis. I guess I got confused because usually in Maya you have to align the master object along the world x-axis when instancing to particles. There's also this line in the docs for the Flight node : "Objects will face down in the Z-axis if you add an orient node." which is correct but could be explained more clearly I guess.

Note that it's still possible for the intances to flip with this alignment when they are travelling up or down.