Join Todd Kopriva for an in-depth discussion in this video Prerendering and using proxies in After Effects, part of After Effects and Premiere Pro: Optimizing Performance (2011).
One way to save a lot of processing power and optimize performance, is to not force After Effects to rerender things over and over again, that it has either already rendered once, and can be done with, or that it doesn't need to render at all just yet. If you have a large movie, such as a red digital cinema sized movie, you can replace it temporarily with a proxy, a lower resolution movie. Or, if you have a bunch of items that you're already done with in your composition, you can pre-render them and replace them with a finished movie. Let's look at proxies first.
In this composition, I have a layer that's based on a red digital cinema movie, and I have four layers, that are solid layers, with the fractal noise effect applied. If I press the spacebar to do a standard preview, you can see that each frame takes rather a long time to render. So, let's speed that up a little bit. First, let's Purge the contents of the RAM cache, so that we can see the results.
Choose Edit, Purge, Image caches. Now, about that proxy. Here we have our red layer. Let's choose Reveal Layer Source in Project, and here it is running from explosion, and we see that its a red cinema file, with this selected Right-click, and choose Create Proxy.
We can either create a Still Image item, or a Low Resolution movie to replace it. Let's go with the Still Item. That adds a Render item to the Render queue. And so if we press Render Now, this will create a single PSD file, a single PhotoShop image file, that will replace the red footage item temporarily as a Proxy item. Clicking Render, yeah, It almost immediately finishes because it's only creating a single still image file. And now, we see for running from explosion, the Photoshop icon, and a filled white box. The white box means that a proxy item is associated with this footage item, and the filled part means that the proxy is in use. If we Click and clear the fill, we see that now the Photoshop item is not used, but the red cinema item is.
If we expand the project panel a little bit, we can actually see that we have both the original footage item and its proxy listed. So now if we Click to fill again, we see that the proxy item is in use. It has the bold heading, as opposed to the unused item, which is not in bold. Let's narrow the project panel back, and now if we go back to our composition, and press the Spacebar to do a Standard Preview, we notice that it goes quite a lot faster, and also the image is not updated.
Let's go back to the beginning of the composition, and notice when I press Spacebar this time, the image does not update in the Composition panel. That's because, this is now a Still Image. When we add this composition to the Render Queue composition, Add to render queue, notice that, under Render Settings, we can choose whether to use the proxy or not. The best settings don't use the proxy.
But if we wanted to use the proxy, we could choose to do so here. In general, you don't want to use your proxies for final output, unless you're just doing a quick preview. So Cancel out of this, and go back to the composition. So, even though our footage layer is playing back pretty quickly, it's still taking quite a long time to update these 4 solid layers, with their fractal noise effects applied. Let's go back to the beginning, and Purge the RAM cache again. And let's say that we're already done with these noise layers, we don't intend to modify them anymore, they look the way that we want. Instead of having layers with effects applied that have to be rendered each time we move to another frame, we can replace the entire set of four layers with a single layer, that is actually a movie that is already rendered. So instead of having to render an H frame, Aftereffects can simply look at the already-rendered movie frame.
Let's see how this works, Select one of the layers, Shift-click to select the rest of them. And now press the keyboard shortcut for Recompose, which is Ctrl+Shift+C, Cmd+ Shift+C on Mac OS. Click OK. Now these four layers have been replaced by a single pre-composition layer. If we Right-click and choose Reveal Layer Source in Project, we see that what is revealed is a pre-composition or a composition.
The difference between a pre-composition and a composition is simply that a pre-composition has been pre-composed from various layers, and is usually nestled within another composition. Let's rename this Four Noise Layers, (audio playing) And then, see that, that name has been updated on the Timeline panel. If we Double-click, and Open the composition, we see that the 4 noise layers are still there, press the keyboard shortcut Shift+Escape, to go back to the containing composition, and we're not done yet, because all that we've done is put the 4 layers inside of their own composition. They're not rendered yet, so now we need to, Prerender this composition. With the Composition selected, choose Prerender.
Now let's remove the render item that we had in here from before, when we were looking at the render settings for proxies. And now we're left with the rendered item, that we just added, to create our pre-rendered layer. I'll accept the defaults which are AVI at best settings, which includes an Alpha Channel. Click Render, and when the render is complete, the pre-composition layer will be replaced by a layer based on the movie, the .ADI file.
Let's go back to the composition and there we are, this layer is now based on the API file. So now if we press the Spacebar to do a Standard Preview, things go very quickly. In general, you tend to Prerender, only after you're done working on something. But you always could go back, and take the composition, and drag it back down in here, and Delete the movie file. If you wanted to go back in and make some changes, I'm going to press Ctrl+Z twice to undo that. Similarly, with a proxy, you don't usually want to have the proxy included in your final output.
So, before you Render for Final Export, you could either make sure that your render settings don't specify to use proxies, or you could just go and Disable the proxy, either way. You might want to do a quick Preview before you send something for Final Export. So I would probably Disable the proxy and just do a quick scrub through, before I sent things out for final output.
- Planning your work, updating, and auto-saving
- Learning and customizing keyboard shortcuts
- Optimizing hard disks and CPUs
- GPU: CUDA and OpenGL
- Using "Render Multiple Frames Simultaneously" multiprocessing
- Pre-rendering and proxies in After Effects
- Lowering resolution for previews