Separate the questions
Lifetime controls when a particle expires. Start speed controls its initial motion. Drag changes how velocity develops over time. Emission controls how many new particles enter the effect. Raising one because another looks wrong often produces a fragile preset that only works from one camera position.
Smoke usually benefits from a visible expanding tail, while sparks often need a quick bright onset and a sparse finish. This does not mean every smoke particle should be slow or every spark should be short-lived. Start from the visual role in the game, then choose a controlled comparison.
| Symptom | First thing to inspect |
|---|---|
| Effect ends too soon | Start Lifetime and the alpha curve |
| Particles travel too far | Start Speed, forces and drag |
| Cloud becomes opaque | Size, emission and overlap |
| Tail looks flat | Variation in lifetime and size, not only more particles |
Run a one-variable experiment
In a Unity test scene, use one material, one seed and one camera. Compare a two-second lifetime with a 0.4-second lifetime while keeping the initial speed equal. Then return to the baseline and compare drag 0 with drag 1. These values are an illustrative test, not calibrated physical units or an assertion about exact cross-engine matching.
Keep Multiply Drag by Particle Size and Multiply Drag by Particle Velocity disabled during the first drag comparison. Otherwise, a change to size or speed also changes the amount of drag and you are no longer isolating one factor. Once you understand the basic result, enable those multipliers deliberately.
- Save the baseline.
- Change only lifetime and record the duration and travel distance.
- Restore the baseline, then change only drag.
- Inspect the result at equal timestamps rather than comparing unrelated screenshots.
A velocity cap is not the same as drag
Limit Velocity over Lifetime contains both a limit and drag-related controls. Dampen reduces speed when particles exceed the configured limit. Drag can act as a continuous velocity influence. They are grouped in one Unity module but answer different artistic questions.
A very low speed limit can make fast sparks look abruptly constrained. Raising drag may produce a different deceleration profile. Compare the trajectory rather than judging a single final position.
Use the browser for the supported preview subset
2VFX exposes random ranges and curves along with portable Unity module fields. Labels distinguish the browser-previewed subset from Unity-export-only behaviour. Trails, Shape and collision-dependent events must be judged after import in the engine.
XYZ groups use a shared curve mode because Unity requires compatible modes within the group. You can still use different values and curve shapes per axis. Do not interpret this synchronization as all three axes having to be numerically equal.
Check the loop, overlap and moving emitter
Play the effect continuously, then move its source. Local and world-space simulations can produce different trails behind a vehicle or prop. Check both dense overlaps and isolated particles to avoid fixing a texture problem with emission settings.
Finally, export and open a saved .2vfx variation again. Keep the model, atlas layout, seed and target pipeline with the example. A readable comparison is more useful than an unexplained list of supposedly universal smoke values.