How is real-time rendering different in blender from game engines?

Question

Real-time rendering is the key feature of game engines like Unity and Unreal. Although advanced rendering by Cycles should take a while, I think Eevee should be able to deliver real-time rendering.

I created a simple SoftBody simulation (the official example) with all default settings. By the game real-time rendering standard, this simple animation should be as fast as 30 FPS.

The first playback with Eevee was as slow as 1-2 FPS (GPU was not used). Full rendering by Cycles was as slow as 0.1 FPS (utilising two GPUs).

I have 16/32 cores/threads and two 1080Ti.

Do I miss something? Can we get real-time rendering (30 FPS) with blender?

Answer 1

Well, Blender isn't a game engine, and it's not designed to perform final animation renders in real-time the way a game engine does. The design goal of the EEVEE renderer is to provide real-time or near-real-time previews and fast (but not real-time!) high-quality final renders. As mentioned on the development page, it uses gaming rasterizer techniques to render quickly, but it is not a gaming renderer itself, and it targets high quality final renders that aren't subject to a fixed frame rate.

So, for the soft-body example above, you should be able to easily achieve a 30 FPS render in preview mode (with full PBR-like materials and lightning, even without baking the physics, since the physics aren't very complicated), demonstrating that EEVEE can, in fact, render animations in real-time by cutting various corners, but the final render with default settings will be higher quality and quite a bit slower (1-2 FPS seems about right). I don't think Blender exposes a sufficient number of settings that would allow you to perform the final render at the same speed as the preview.

You could request such a feature (basically a checkbox to reduce the final render quality to the preview-level quality), but I don't think there would be much interest, because most Blender users aren't looking for real-time final renders; they just want fast previews. That's because they're either using Blender to develop assets for true real-time game engines (and so just need a fast preview to see what they're doing and have no intention of using Blender for the final render), or they're planning to render a high-quality still image or fixed animation and want to prioritize render quality over render speed.

Answer 2

Eevee is not that much evolved yet, also blender has made it for previewing final and much more realistic results than game engine which focuses on making you visualise things and approximates much more than eevee for a faster playback also the thing you should check is that you have already baked the animation in blender so that it is not calculating everything while playback as most of the game engines try to calculate as much feedback as possible and keep that in the memory because of which they even require high amount of memory compared to eevee and don't have to calculate many things while playback is going on.