Pre-composing – Instruction resources

[Andrew Kramer]

Pre-composing,
One way to think about precomposing is to “temporarily flatten” a group of layers. By flattening this group you now can apply effects to these layer as one. Another way to think about it is like rendering out a sequence with a group of layers then importing this back in, the benifit of pre-composing is you can make changes dynamically.

Another important aspect is the continuous rasterazion button or the “collaps transformations” switch. If you have text for example, by switching on the continous rasterazing switch you can scale up the precomp and the text wont get blurry. antoher thing that happens is the effect parameters re-render around the parameters of the precomp in the new composition. (like if the scale is larger, a glow wont get bigger but instead be as large as it was in the previous comp)Also global settering must be set inside the pre-comp like motion blur and layer switches to be rendered insed of a new comp when set to continously rasterize.

Important things to note:
1. In the preferences you can shut off “synchronize time of all related items” and this each precomp can have it own time indicator, instead of dynamically changing, I prefer it to dynamically change for most things, but the option is nice.

2. Keyframe interpolation for effects inside a comp. For example if I use trapcodes, particular and I have some smoke rising, If I pre-compose this and then slow it down to 200 percent with the continuous rasterize switch on, the plug-in with render intermediate frames, sometimes this is the only way to achieve certain effects.

3. 3d layers can be pre-composed and then moved in 3d space from another comp. Example: say I create a box out of 6 layers then precompose this box (with the 3d layer switch on) I can add a new camera to the apparent frozen 3d element, but then turn on the continuous rasterization, and now you camera can move around the box, and by changeing the position you move it in 3d space as well instead just a “flattend box” you can also turn on the 3d switch and then move the layer around better in 3d space. the cool thing about this is for somet things it makes managein many layer easier when using repiticious elements.

4. Preserving transfer modes when pre-composing, Exapmle, when you use transfer modes to interact with layers below a pre-comp will disrupt this synergy, by continuously rasterizing the transfer mode will now interact with layer below.

5. Certain effects need to be pre-comped inorder to add other effects like masking. When using and effects that sources the actual original clip instead of the order it sits in the effects controls window. This method of rendering for the effect is essential in some cases but limiting as well. for example, If I have a clip and then I apply an instance of “levels” to color correct and then I add a revisionfx fielsdkit deinterlacer, this plu-in samples from the original source and disregards the levels adjustment, the solution here would be to apply the levels after the deinterlacer but this doesn’t solve every solution, If you have ever tried to apply a mask to a layer with one of these original source sampling effects you know what I mean. the mask will apply itself but nothing will happen. In this case it’s best to add the effect, then pre-compose then add you mask.

6. Do not over pre-compose, use it when necessary, don’t just pre-comp a pre-comp and another pre-comp, be wise. It can waste a lot more cpu power if overused. Optimize the need.

7. The leave attributes option is handy, just think about what your doing and this method will come in handy

8. “alt” + double clicking on a pre-comp name will open that pre-comp, you can also click on the layer itself but you may rist accidently shifting layers,

9. Understand that a pre-comp isn’t always the best solution, sometimes it might be better to render out the layers then re-import, after effects render out the pre-comps then you secondary effects so you might waste valuable processes.

10. Pre-comps can also be necessary for effects that sample layers image data, For example, If I’m using a compound blur and I want it to use a black to white gradient, First i need to make a new layer, add a ramp effects and then tell the compound blur to use that layer as it’s “blur layer”, however the effect will only sample the layer itself, I need to pre-compose the effects so the compound blur sees, A “flattend Layer”.

There is more to this important technique perhaps other can add to this list.

good luck
Andrew Kramer

[Joeythedog]

Gee Andrew Thanks You didn’t need go to such trouble. I appreciate it.

I was just wondering if there was an article or tutorial.

Thanks

[Kathlyn Lindeboom]

[JoeyTheDog] “I was just wondering if there was an article or tutorial.”

We have several tutorials in the library about precomposing. Just click on the After Effects COW banner above.

Kathlyn Lindeboom
The Mistress of Mmmooooo!