Particle Strip based trail has holes/discontinuities for no clear reason.

Hi,

I'm trying to utilize VFX Graph to create a simple trail following an object, as a part of an effect.

For current test purposes, I have an extremely simple setup, with some coloring added for debug visualization.


For the most part, it works as expected, with a trail of evenly spaced quads being produced. However, there are discontinuities appearing in the trail, in a stably reproducible manner. The trail is connected to a on object that flies through a game world driven by a simple rigidbody with given starting velocity and the result can be seen on this screenshot:


So the mesh looks pretty clean and the color is as expected, but there is a gap of what looks like two quads of size and I struggle to find an explanation, not to mention a solution, for this issue.

My main work environment is Unity 2020.3.12 with VFX Graph 10.5.1, though I tested it also with 2021.1.13 + 11.0.0 with the same result. I'm using the URP, if it's of any relevance to this problem.

I tried to uncheck "Fixed Delta Time" on the effect, to no visible change.

I would appreciate any info about what I'm doing wrong here and what would be the direction to fix it.

 

Hi Julien,

thank you for the quick reply.

I figured that since the issue is caused by more than one particle spawning in the same place, I can try to space them out retroactively. I ended up with a solution that seems to do the job:


What baffles me here is that I expected an index needed in this context to either be spawnIndex (Source) or spawnIndexInStrip (Current), but using either of those resulted in the trail breaking in a different way. Meanwhile, using spawnIndex (Current) seems to do the trick. Can you perhaps give me a bit of context for how those attributes behave and differ from each other? Because unfortunately the documentation seems to be of little help on the subject.

 

wow that's super clean solution, and works in versions of vfx graph that don't have clamp to 1