How do I check for LOS to object hitbox?

I like that kind of problem.

One idea is a rough LOS check. Basically repeatedly pick a random point inside the collision poly a do a LOS with that. Would fail more with smaller loops if the object is obstructed but it may give a true eventually. Could be a useful approximation of vision. Anyways the main sub problem to solve would be to get a random point in a polygon.

A second idea is to utilize raycasts. Either a uniform spread of rays in roughly the direction of the object or use a bit of random. If any of the rays hit, there is LOS. I think this one is the most doable. Not sure if the ray cast feature in c3 can be used for this but making a ray cast with events would work.

Another idea if to calculate the view polygon from one point and check to see if that view poly overlaps an objects collision poly. May be tricky to calculate though. One approach would be to do what shadow casting does and clip away from the collision poly the shadow bits. This would give an absolute is in in Los or not check.

Anyways just some ideas, each with their own set of sub problems to solve. Maybe some are useful.

I've done something similar before. The solution I settled with was to set imagepoints at every corner of a los blocker, the cast rays immediately before and after every corner in range. Then see if any rays collide with the object in question. The key is that you're casting rays at the obstacle corners, not the target object directly.

Depending on the sizes (and distance) of the origin and target objects, you can further cull the rays cast by only checking the corners in a certain direction, within a set range of angles from the angle between origin and target.

It ended up much more accurate and higher resolution with less rays cast than trying to cast rays every x degrees in all directions, and more reliable than casting rays at the object.

An alternate solution could be to cast a fan of rays towards the target object, wide enough to envelop the object. If the target is a fairly square or round shape you could set the bounds of the fan based on the distance and width/height of the target, then cast x amount of rays based on the desired resolution (or by distance, since you probably want higher resolution the farther away the target is).

Edit 3: For further (significant) optimization, first check to see if the target origin is in los directly before casting any additional rays at all.