Difference between CC Force Motion Blur and Pixel Motion Blur?

[Finomnom]

As the title says, what's the difference between CC Force Motion Blur and Pixel Motion Blur? 

[Mylenium]

You could just try yourself? CC Force Motionblur generates actual sub-samples by slicing a frame into sub-frames whereas pixel motion blur determines the motion vector of a set of pixels to "smear" them and give the illusion of a motion blur trail.

Mylenium

[Rick Gerard · Accepted solution]

CC Force Motion Blur renders faster than Pixel Motion Blur because PMB calculates motion vectors. It does a fair job but you need to adjust the number of samples based on the motion of the layer. The more samples you take the slower the render. If you are trying to precisely match the motion blur of something on the footage then Pixel Motion Blur is probably your best option.  The first thing that you have to do though is to match the number of Shutter Samples with the number in your Comp composition settings. The default for Pixel Motion Blur is 5 and CC Force Motion Blur is 8. I prefer at least 16 samples in the comp settings. 

When you have matched the number of samples, check the result of Force Motion Blur against the rest of the comp. If it looks good on a frame, preview the motion. If you think you need a little better match then try Pixel Motion Blur. If the motion is fast, you are going to have to adjust the Vector Detail to get things to look right. There will be slight differences. The yellow layer in this screenshot is the one with Pixel Motion Blur and a little tweaking gave me a curved edge to the rotating pointers. The curved edge is a little more realistic but the render time is about 3 times longer. You have to decide if it is worth it.

The difference in render time is significant if the samples and Vector Detail go up so be ready for longer renders.