Very old topic, but had the same question myself today and didn’t find an answer online. After a big of messing about though, managed to get it working by repurposing a static mesh to act as the volume - thought I’d leave the steps here in case like me, this post was top of the list.
- Copy a basic static mesh (Basic 1x1 cube for me)
- Adjust the mesh settings etc so that it’s not visible, collision to OverlapAll, size/scale and all of that (although you can probably set this to be more dynamic / align with something like a river as mentioned in the initial post in the next step)
- In the blueprint with your spline, in the construction script, just add this new mesh along the spline as you would any static mesh, spawning it at every distance x
- Add in your ‘OnActorBeginOverlap’ etc events or whatever it is into the blueprint event graph, and it should work nicely
Note that I had performance issues when making adjustments to the construction script (at least after it had been placed in a level), might be worth having a parameter in there somewhere that you can switch collision on/off in the world outliner or something like that, or only enable the collision once everything’s been set up, your spline is in your level and you’re not likely to it move again.
Hope that helps anyone with the same question.