I am trying to achieve a fireball that fades out. I have found multiple particle emitters that create the fireball. So far no issues.
The problem that I can't seem to solve is that I would like the fireball to grow in size as it fades out (i.e. increase scale as opacity is reduced).
However, the particle emitters don't have a scale option. Most of them have a size but the size is not recorded on key frames so setting it on any key frame changes it for the whole project.
I even tried making the emitter attached to a dummy parent which I scale up. Typically that causes attached objects to also scale, but the emitter didn't.
Any suggestions on how I can achieve my goal?

"We often compare ourselves to the U.S. and often they come out the best, but they only have the right to bear arms while we have the right to bare breasts"
Bowser and Blue, Busting The Breast

ANY suggestions?  Or just those that relate to particle emitters?

I'd use a billboard with footage, free, from here: http://productioncrate.com/

They have some great explosions, including some very nice fireballs (that do fade out).  And you could scale the billboard as you wanted.

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Alienware Aurora R12, Win 10, i9-119000KF, 3.5GHz CPU, 128GB RAM, RTX 3090 (24GB), Samsung 960 Pro 4TB M-2 SSD, TB+ Disk space
Mike "ex-genius" Kelley

Actually You can't scale the emitter. You have only 4 keyframes to scale the particles thru the life (frame).
About Particles , this is the only update feature now (before mirror) I expected for Iclone. All what I need for
my pipeline will be in the 7.1 

It looks like particle emitters also ignore other objects. I posted on this elsewhere but I tried to confine the particles to a mesh by placing the particle emitter inside the mesh...no go. Then I tried to have them at least shifted by an object mesh so I placed the emitter under an object...again no go. The particles seem to go through any object they encounter as if it was not there.

"We often compare ourselves to the U.S. and often they come out the best, but they only have the right to bear arms while we have the right to bare breasts"
Bowser and Blue, Busting The Breast

Yes that's thrue Lord. There's no collision detection on this particle system.
What we need for the next particle system is:
Point
Cube
Sphere
Mesh
For the shape of the emitter.

Beam
Trail
Point

Collision detection
Sprite atlas as texture

Shape over speed
Vectorfield

Etc...

I did find a way to somewhat do what I wanted...
I found out that if you turn an emitter off, it stops emitting but any particles already emitted remain until their life cycle ends.
As such, I gave the particles an extended life and a larger volume and then turned the emitter on briefly and then turned it off.
This generated a lot of initial particles which slowly died out which caused the appearance that I was going for.

"We often compare ourselves to the U.S. and often they come out the best, but they only have the right to bear arms while we have the right to bare breasts"
Bowser and Blue, Busting The Breast