2D Motion Blur?

Foxstep Posts: 2
edited March 2017 in Post-production techniques


I setup an animation in another program that is mostly vector imagery and definitely all 2D. It's essentially motion graphics. There's spinning and fast movement, and it's in need of motion blur to make it easier on the eyes.  I came across the suggestion of Hitfilm and it looks like it could help me out.

With the exported video, I tried to play with Motion Blur. However, I notice I end up with a sort of "jitter" or off streak here and there. I've been playing with the settings in both edit and composite mode, and putting it on Custom and maxing out Samples seems to be the best I get. Those annoying things happen a lot less frequently and things look pretty good, but I wonder if I can do better still.

The user guide doesn't really talk much about how to use Motion Blur or the Optical Flow options. I feel I might be pretty close, but maybe some extra input would help me get the rest of the way. (Or maybe this is as good as it gets and I need to figure out how to edit out the off spots.)

I am using Hitfilm 4 Express, if that is important. Any pointers in the right direction would be appreciated. Even explanations on the meanings of the different options within Motion Blur and Optical Flow would be of help.


  • Foxstep
    Foxstep Posts: 2
    edited March 2017

    I guess I can more clearly ask for elaboration on Motion Blur and Optical Flow. Maybe someone can at least help me with that?

    Motion Blur

    Here in the user guide: https://hitfilm.com/reference/hitfilm-4-express/index.html


    • Off
    • Comp Settings
    • Custom

    From what I can see, Comp Settings means that Shutter Angle, Shutter Phase, and Samples are pre-determined?

    The user guide talks about Shutter Angle and Shutter Phase. It says, "For realistic motion blur this is best kept to half the value of the shutter angle." I notice Shutter Angle goes from 0 to 720 while Shutter Phase can have negative numbers. What is "half" then? And what exactly is "realistic"? (For any scenario, or more for 3D?)

    The user guide talks about user adaptive samples and max number of samples. However, Hitfilm 4 Express just has "Samples". What exactly does that stand for then?

    Optical Flow

    • Window Size
    • Sigma
    • Interactions
    • Downsamples
    • Start Downsample

    What exactly are these?

    Looking in the user guide, I can find that Window Size and Sigma help with rolling shutter: https://hitfilm.com/reference/hitfilm-4-express/index.html?text_layers.htm

    Any input is appreciated.

  • Triem23
    Triem23 Posts: 20,610 Ambassador

    41:37 in this video answers half your questions--Shutter Angle/Phase and (Adaptive) Samples, as well as showing you how to set master Motion Blur settings for the Composite Shot (Comp Settings). 

    Optical Flow breaks up the frame into rectangular patches for analysis. Window size is the size of each patch. Larger is bigger. 

    For the rest of your questions, there are eight or nine different mathematical solutions for optical flow. It would depend on exactly which equations the devs are using. It also depends on how good your ability to understand higher-order differential equations is.