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ceznov
Inspiring
July 31, 2026
Question

Inconsistent CPU usage during render

  • July 31, 2026
  • 2 replies
  • 14 views

Hi, 

I animate motion graphics in AE, based on imported Illustrator files. I’m trying to figure out why some of my comps are rendering with very low CPU usage while others peak to 90%. What is strange it looks like more complex comps are rendered super slow (5% CPU usage) while others that has much less layers and effects can use much more. But still even through those lite comps the CPU can jump from 5% to 90% for no reason - meaning nothing really changes in the comp exept some layer movements… how can it be?

I render into PNG sequences inside AE.

Sometimes I use BG Renderer MAX that forces AE to use as much CPU as possible, but this plugin often crashes or misses some PNG files so I’d rather use built in AE renderer. But it is inconceivable to me that 3rd party plugin can make use of the whole CPU, while native AE can’t :/

    2 replies

    ceznov
    ceznovAuthor
    Inspiring
    July 31, 2026

    BTW. one thing helps for some time, but I really don’t understand why. If I restart AE and start render ing immediately after, it runs very fast for a while, doesn’t matter what comp is rendered. But I don’t get it - does AE get clogged during normal usage so it need to be restart before every render? I always clean all the cache and memory before render, thought it should be enough...

    Community Manager
    July 31, 2026

    Hi there, ceznov,

    Thanks for the message. CPU utilization during rendering can vary quite a bit depending on what's happening in a given frame. After Effects isn't designed to keep all CPU cores saturated at all times. Some operations are highly parallelized, while others are limited by a single thread, disk I/O, or waiting on the GPU, so it's normal to see CPU usage fluctuate during a render.


    A few questions that may help narrow this down:

    • Which version of After Effects are you using?

    • What are your system specs (CPU, GPU, RAM, and OS)?

    • Do the slow renders contain any third-party effects, expressions, or motion blur?

    • Are the Illustrator files linked or embedded, and are they particularly large or complex?


    Regarding the improvement after restarting AE, that isn't generally expected behavior. If it consistently renders much faster immediately after launching the application, it would be useful to determine whether this happens in a brand-new project with a simple test composition as well, or only in this specific project.

    The answers to the questions above should help determine whether you're running into a project-specific bottleneck or something that may warrant further investigation.


    Thanks,
    Kevin