OpenGL Causing Quality Loss?

[Darby Edelen]

The answer is: never use OpenGL for final renders. Even if all OpenGL features are supported, that feature set is not as complete nor functionally equivalent to the CPU based renderer.

Darby Edelen

[Richard Christy]

I see. I wasn’t aware that OpenGL wasn’t intended for final renders. I knew you could balance it between more preview length and quality, but I would have never guessed not to use it for final rendering.

If I need to use it in a pinch to save time, what kind of quality loss can I expect? It is the equivalent to applying a standard codec?

[Tudor “ted” jelescu]

The advice from Adobe is to keep OpenGL off. Most folks on this site will tell you to do that as well. My advice is get more RAM (at least 16GB total- with 4GB you can use one core only) to take advantage of multiprocessing and thus faster renders.

Tudor “Ted” Jelescu
Senior VFX Artist

[Walter Soyka]

Adobe warns against using OpenGL for final renders in the documentation, but I do agree that the warning should be in the application as well. From Render with OpenGL [link]:

Important: Because not all features of a composition can be rendered with OpenGL—and because some features that can be rendered with OpenGL are rendered with different results—you may only want to use OpenGL rendering to accelerate previews and to provide faster rendering for non-final results.

[Richard Christy] “I knew you could balance it between more preview length and quality, but I would have never guessed not to use it for final rendering.”

I think you are thinking of AE CS4’s memory settings, where you could adjust between faster and longer previews. AE’s OpenGL renderer does not have any quality adjustments.

[Richard Christy] “If I need to use it in a pinch to save time, what kind of quality loss can I expect? It is the equivalent to applying a standard codec?”

Not really — the AE OpenGL renderer won’t degrade your image in the same way that lossy compression would.

The OpenGL renderer is not just a lower-quality, but faster version of the CPU renderer. The main problem with the OpenGL renderer is that it doesn’t support all the features that the CPU renderer supports, and that different graphics cards may produce different results from the same scene.

In other words, results from the OpenGL renderer are dependent on both the scene and the graphics card rendering it, and they may or may not resemble results from the CPU renderer for the same scene.

If you were to use the OpenGL renderer to get a client approval for something, you might be surprised to see that your scene looks totally different when using the CPU renderer. If you really want to use the OpenGL renderer, I would rely on it for position and movement only; the overall look could render very differently on the CPU.

Instead, I’d note that 4 GB is a very small amount of RAM for AE work. AE performance more or less scales with hardware, so a fast machine with multiple cores and a 2-4 GB of RAM per core will let you use multiprocessing [link] for faster, high-quality renders.

If you’re looking for better performance from AE, I’d suggest you read through the Improve performance [link] page, which is full of suggestions for tuning your computer, After Effects itself, and your workflow for the best performance.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
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