Particle trace report
The PopcornFX editor has a few tools to help debug particle systems.
One of these tools is the trace report. It allows you, at any time, to inspect the properties of individual particles, using mouse-picking or rectangular selection in the realtime viewport. It can be a powerful help when used in conjunction with the particle history, allowing you to trace and inspect previous frames, in case you spotted a glitch and want to make out the cause.
(you can also see the trace report video tutorial)
To use the tool, you just need to pause the effect (Hit F2 in the viewport), and left-click on the particle you wish to inspect, in the realtime viewport. The values of all its fields will appear in the "TraceReport" panel, located on the middle bottom panel of the default layout, under the second tab of the attributes panel:
The trace report panel provides various tools and buttons:
The picked particle will have red outlines rendered (matching its billboard's triangles). However, unless the particle system is very sparse, there most likely won't be a single particle picked. All particles hit by the picking ray will be highlighted with light white outlines.
You can cycle through all traced particles by repeatingly left-clicking on the same spot. If you move the mouse between two clicks, a whole new trace will be cast, and cycling will start over.
The ray used for picking is also rendered as a bright red line, due to projection on the screen plane, it appears as a single red pixel, but you can visualize it better by moving the camera around:
You can also use a rectangular selection by left-clicking and dragging the mouse in the viewport for a more precise picking. The rectangular selection will only consider the particle centers.
Picking is affected by layer visibility. This can be useful if you wish to isolate a specific layer out of a big mess.
In the example below (the Blast.pkfx, coming in the default FX sample package), we trace the 11 different layers (8 main layers + 3 sub-layers that are trail spawners in the 'Debris_Smoking' layer).
The result is pretty horrifying, and it can be tedious to isolate a specific particle. Here, you can see the ray picked 64 particles:
If we hide the layers we're not interested in, we can pick only the smoke trails layer, and the result is much easier to work with. Only 9 particles were picked: