[Arelius]

Sure, if you can render at so 120 hz, or more and composite the 4 frames together into your single frame you will get a single improved frame. but even at 4 renders a frame you'll still get artifacts, I imagine you'd need at least double to make it worthwhile, But even that only gives you ~8ms to time step and render the entire scene. Minus composting and any other full-frame post effects. And hitting the ~16ms required for a 60fps is already pretty difficult.

Now, in video games we do have methods to help simulate inter-frame motionblur. The most commonly used is to build a buffer of inter-frame motion vectors, this is often generated with game state, but can also be re derived by analysis of current and previous frames to some affect. Then you do a per-pixel blur based on the direction and magnitude of the motion vectors. Which often works to good effect.

[KayEss]

You wouldn't need to render the whole frames. You'd get even better results from randomly sampling over a number of frames to contribute to nearby pixels. In effect you're trading less work for more noise, and noise is kind of what you want here (so long as it accurately reflects what is happening).

So, you could render 16 samples, but only do 1/4 of the pixels on each so you'd get better motion blur for only a small increase in work over doing 4 temporal samples. The extra work corresponds to a bit of bookkeeping and the tweening of 16 frames instead of 4 and you'd still be rendering the same number of samples overall.