DOPs Order of Evaluation Misunderstanding (Solved)

[DeeLan]

I'm currently following along with Rohan Dalvi's Motion Graphics tutorial, and I've run into two issues with the particles from the outer ring that I thought would have simple solutions, but so far have completely stumped me.

The first thing I've found is that each point would spawn two particles, resulting in two lines very close together, and I want to get only one particle/line for each spawn.

I've figured out the reason for this happen is that in my POP network I do two separate replicates, each on a different particle stream/group (so that I can have differing life lengths), and the replicate POP passes through the original particles (even those no being replicated) so after merging the replicates back together, I end up with two separate sets of the original spawner particles. Now the solution I came up with was to remove the points I didn't want to replicate, do the replicate for each group, then merge them back together (exactly like I would if I had this issue in SOPs). Problem is though that didn't work at all. I tried both Kill POPs and POP Wrangles, and a few different setups but nothing worked. I've included some notes with the scene file to give better explanations.

 

Secondly, when the spawner particle collides with the tube, the replicator keeps replicating it, so we end up with a bunch of points stacked on top of each other, which I don't want.

My idea to fix was to have a node placed straight after the replicate that removes any particles in the "hitparticle" group from the "stream_General_Spawner" group. That way, on the next frame, all the collided particles won't be replicate again.

But this didn't entirely work either. "Combine Groups" on the Group POP almost did the trick, but in addition to removing the particles from the spawner group, it also removed them from the hitparticle group, which I don't want because I have a wrangle that does stuff with that group.

 

Does anyone know why these issues exist? I'm guess that I'm missing some sort of foundational knowledge on how POPs work? Any recommendations for tutorials or articles to go along with the documentation to help with this?

POPs_problem.hipnc

Edited October 13, 2017 by DeeLan
Clarification of Question

[DeeLan]

So I think my issue may be with how streams work (still figuring it out). I've been trying to read and write the value of the stream attribute using @group_streamname but it won't allow me to do that. I understand not being able to modify the attribute, but why wouldn't it let me read it?

[DeeLan]

So it turns out that the issue was I didn't realise that DOPs actually shares data between different paths of execution (not sure what the actual name was), and that merges share the data left to right. because of that the spawner particles were completely gone by the second frame which gave me the messed up results. Its all fixed now though.

POPs_stream_problem_FIXED.hipnc