Select all 3 explosion layers.
We are going to nest these layers into another composition by pre-composing them. Again you have two options! You can either right click and select 'Pre-Compose' from the context menu or go to the main menu and select Layer-> Pre-compose...
I am going to call this new composition 'Explosion Group Comp'.
Note that we are given two options.
Note that our 3 explosion layers have been replaced by a single layer called 'Explosion Group Comp'.
This is our newly created composition and it contains our 3 explosion layers. If you go to the Project Window you will also see the newly created 'Explosion Group Comp' composition in there.
You can open the composition by double clicking on it, either in the project window or in the timeline. You will see the 3 explosion layers we pre-composed inside of it. Note that they are still at the same positions and timing as when we originally set them up.
If we now return to our original composition and scrub through the effect, we will see our 3 explosions appear like before. However, they have regained their ugly black boxes! This happened because the new composition we created is set to Normal blend mode.
We can fix this by setting the blend mode back to Add.
Now this might look exactly like it did with our 3 separate explosion layers, but this setup allows us to assign the Glow effect to the explosion Group Comp layer and it will apply to all of our explosions. Again, increase the Glow Radius and Glow Intensity and lower the Glow Threshold so you can see the effect clearly.
We have used the composition to group together our explosions and we can now treat them like a single layer.Besides pre-composing to nest compositions, you can also drag one composition into another, given that you are not creating a circular reference.
Go back to the project window and drag another copy of the Explosion Group Comp into your composition. This will add another 3 explosions into your scene!
Set the blend mode for this new layer to Add to get rid of the black boxes again. I am also going to flip this layer horizontally so the explosions don't line up exactly.
Offset this second explosions group by a little bit so we end up with 6 consecutive explosions all happening at different times and in different spots in the scene.
Scrub through your footage and a barrage of explosions should appear! Note that if we disable the visibility a single Explosion Group Comp layer, we hide all elements inside of it. By hiding a single pre-composed layer, we are hiding all 3 explosion layers inside of it.
Have you noticed that only the explosions from our first Explosion Group Comp have the glow effect applied to it? Again if we wanted the Glow effect to be applied to all 6 explosions we will have to copy it across from the first layer onto the second one.But again that would not be a smart thing to do. Instead, we can pre-compose our layers. Note that we can pre-compose any type of layer, whether it is footage, text, solids, shapes or other compositions.
Before we do this though, first delete the Glow effect from the Explosion Group Comp layer.Now select both Explosion Group Comp layers and go to Layer -> PreCompose.
I am going to call this new composition '6 Explosions' and hit 'OK'.
Set the blend mode back to Add on the new composition. This layer now contains two Explosion Group Comp layers which contain 3 explosion layers each.
Since I'm getting bored of the Glow, let's instead add a Tint effect to the 6 Explosions layer. You can find the Tint effect in your Effects & Presets browser.
Change the Map White To property to a funky colour like blue.
All 6 explosions in your scene are now... um... strange blue puffs! They look like ghost explosions
Not particularly pretty, but I just wanted to show you that you are free to pre-compose any elements that you want.