(VERY) Basic speedlines question

[creative_vision]

Hey

I'm new on here and new to video editing and have a very basic question.

My 5 year old son is currently obsessed with Sonic and everything fast. So I'd like to make a video of him runnng and then add 'speed lines' behind him to make it look like he's going really fast.

Ideally something a bit like on this advert for this game (which he also now has asked for, in the expectation that it will allow him to run exactly like that .... yes with the lines showing up behind him )

https://www.youtube.com/watch?v=GXBZslg5IP4 (the speed line trails start at around 20 seconds or so)

I've got a MacBook Pro and iMovie and Affinity Photo but not much else. Happy to get more if reasonable.

Any help or pointers much appreciated!

Thanks

Amer

[Cornucopia]

One way to do it:
Shoot with a locked down camera. Shoot the area first without the subject (called the clean plate) then with the subject.
Create a travelling difference mask using the clean plate as the difference background.
This will give you a video of the subject only with no background, like a transparency.
Make "ghost" images by copying this image as top layer, then making more subsequent weaker-opacity copies each shifted later in time, in the layers underneath. You could also colorize them on a single color to give this similar illusion to the example.

Normally you would do something like this in AfterEffects, but that is probably too expensive. You could do it in avisynth (I've done something very similar to that using it), but that is windows only. On mac, the nearest equiv to AE is Motion, also $$.
You might be able find some canned effect that can do this that works on mac, but I don't know what that would be. Sorry.

Scott

[johnmeyer]

You might be able to adapt the "motion blur" available in some NLEs (like Vegas) to do what you want.

https://www.youtube.com/results?search_query=sony+vegas+motion+blur+effect

[Cornucopia]

You may want to look up one of our past threads - do a search on "ghost trails" and it should come up. Has similar features. Much of this stuff is not what I would call basic, though.

Scott