So this is just a random thing that's bugged me for a while and I assume there's probably something I don't know that I should...
I generally try to avoid using Nulls, Solids, and Adjustment layers in favor of doing the same job with shape layers instead. As far as I can tell, shape layers can do everything these layers can do and more, plus they don't clutter up my bins with unnecessary assets. So I’m wondering why they need to exist at all? And if there’s any difference between the 3? An adjustment layer seems to just be a solid with the adjustment layer toggle on. And a null seems to just be a smaller solid with 0% opacity. I can see how this might save time instead of creating a solid and then making those small changes to get the same result, but why not just make them all from shape layers instead?
The odd time I do use nulls is generally when I'm using the generate nulls from paths script, which in a recent project generated 60 nulls. of which I replaced nulls 2-60 with null 1 and deleted the rest to keep my project tidy since there seems to be no need for individual nulls when you can just use the same one for everything.
Is there some useful property that sets these layers apart from shape layers? And a reason generating multiple nulls is necessary instead of just 1?
This is just a curiosity to me really but if anyone has an answer I’d love to hear it!?
Well, you have basically things backwards, no offense. Solids and Nulls have existed ever since the very beginnings, adjustment layers were introduced in the old AE 6.5, if I rember correctly, whereas shape layers only debuted in CS3. So you see, they have been there and had their purpose long before shape layers were ever dreamt of. That aside there are several technical reasons to have them and of course all sorts of backward compatibilty considerations. A few are:
accessibility with and from expressions
easy access to properties with the Shift+P|S|R shortcuts
customizable label colors
rendering order and behavior on regular layers vs. dynamically rasterized layers like shape layers
response to certain layer switches and combinations of stuff
click registration when selecting items in the comp window
See? There's a whole slew of reasons why these layer types exist and should exist. A character animator for instance might simply prefer direct access to keyframes on Null rather than drilling into endless shape layer groups. Also shape layers are just container always restricted to the size of the comp, so content gets clipped off. None of that happens with solids for instance and they can be many times larger than the comp even which is useful for e.g. replacing skies in a 3D-ish environment or otehr such stuff. Could some things be consolidated and improved? Sure, but at the same time nobody in their right mind would want to get rid of these alternate layer types as there are clear use cases for them.