Ive created a Particle System which creates a central flare, a burst ring, sparks, and a plume of fire.
In order to get the fire to plume out in the specified direction, I used a velocity/life module.
No matter what settings I apply, the plume in the preview window is always delayed by 0.5 seconds.
I found the time of the plume’s errant delay by delaying the other modules, via the ‘Required’ module, to match when the plume occurred.
When the delays are set to: 0.0 for the plume, and 0.5 for everything else, the effect plays correctly.
However, the plume’s Velocity/Life delay does not occur in PIE.
In the preview, first the ring and flares play out:
Then the plume 0.5 seconds later:
As you can see the ring and flares are long gone by that point.
Yet when testing in PIE, the system plays without the errant delay:
As I am working with 4.8.3, I am unsure if this issue is resolved already in more recent versions and I apologize if this is the case.
One possibility is that you are not running at EPIC in your Engine Scalability settings which can be found under the Settings icon at the top next to the Blueprints Icon. This is the most likely cause if the FX works in PIE but not in the Cascade Preview Window.
Alternatively, I would set up your Flame Plume to use Local Space (in teh Required module) and use just Velocity to control its movement as I want along the X axis, then if it is using Local Space, where ever I spawn the Particle and however I rotate it, the Forward Facing Emitter Arrow will dictate the direction that the Plume expands; it is locked to the specific local axis you see in the Cascade window.
My editor is already running at epic in all categories.
It apparently has been since install since I wasn’t even aware of that settings window, and everything was already set to epic when I checked. lol
Checking ‘Use Local Space’ on and off had no effect on the delay in the preview window.
One odd thing I noticed:
I switched to the ‘Initial Velocity’ module(I didn’t know what you meant by “just Velocity” since there is only initial, cone, inherit, and over life velocity modules ) And that caused the particles to start offset from center, equal to the set velocity, such that they would travel to and reach the center point at exactly the same delay regardless of what velocity I input.
My apologies about the Velocity confusion, I did mean Initial Velocity. Are you using Initial Velocity and Velocity/Life? For what you are wanting to do you can just use Initial Velocity and with Local Space set to true, your particles will not wiggle as your character moves around.
You can see the difference in wiggel from the two placed assets in the level by rotating them or you can Play in Editor and Press K and see how the Local Space Module works attached to the Characters Bone.
Local Space is currently set to true.
Im using Velocity/Life but not Initial Velocity.
In the Velocity/Life module Absolute is set to true, and is using a Vector Uniform Curve to directly set the velocity at specified life times.
If I add Initial Velocity to that the particles start offset behind the emitter equal to the set velocity, then travel to and then pass the center point ~0.5 seconds later. They pass the center point at the ~0.5 second delay regardless of the value I put in for Initial Velocity and the resulting offset.(they just travel faster to get to center)
While I appreciate the example test, This particular particle system is not intended to ever move. It is meant to be spawned at a location and play out at that location. (it is not attached to the hand seen in the image, it is a quick burst that remains stationary and floats at that point)
So “wiggle while moving” is not the problem Im having.
The particle system actually runs correctly while in PIE anyway.
The deviation occurs only in the Cascade Preview Window and is creating difficulty in setting up new particle effects, as I have to load up PIE every time I want to see the end result.
My apologies again. I was attempting to give you a workaround to avoid having to use Velocity Over Life at all.
The offset from center is related to the spawn/tick order of operations. With high velocities, small variations in frame rate during spawning make a huge difference. The biggest issue is that, with framerate variations, the initial spawn location can vary substantially because we update particles immediately after spawning - so the first time the emitter runs, it’ll spawn from the initial location that has already been updated by the velocity, which is large, which is going to offset the initial particle substantially from the origin.
The Spawn Tick Order of Operations is a backlogged feature request listed as UE-4523. I have added your information to the request.
