How to edit to show path of a moving ball?

mjremijan

Does anyone know if VideoPad can be used to edit a video to show the path of a moving object, such as the ball in this video? https://vimeo.com/44572572

borate

'Persistence tracking' - not identical but somewhat akin to the trail in your clip - is possible but tedious. It involves creating a series of still frames of the transparent png overlay along the motion trajectory and stacking them at appropriate locations on the timeline.

Ball_track.mp4

mjremijan

ya ok that makes sense. It is a bit tedious but I tried it on a small scale and it will work ok. As long as the camera stays still 🙂

borate

The overlay can track the plotted motion. Much depends on your level of persistence and patience. ^_

And if a more caterpillar-like motion is desired just repeatedly overlay and offset the insert animation track - no stills needed.

Ball_track1.mp4

[deleted]

There is another way... This uses one ball image and Position keyframes so only uses a single track instead of multiple overlays. So it shows only movement and not a series of images but its simple and perhaps worth looking at.

Place the background image/clip on Video Track 1
Create the ball. In this example it is a simple image of a red circle on a coloured background, dropped onto Video Track 2; Green screened to remove the background and Scaled down to size to suite the underlying image/clip. This is then Positioned to be in the starting position, using the sequence preview to monitor the position. A snapshot is then taken of the Clip image (the positioned red ball) Video track 2 is cleared and then the snapshot placed on Video Track 2 The ball is now in its starting position when the Sequence preview is checked..
Now we add a Position effect to Video Track 2 (the ball in the starting position) Set the first keyframe.
Move the effect cursor line along the clip.
Reposition the ball and set a second keyframe
Repeat the procedure to the end of the clip.

That's the basics and it's is fairly straightforward. But it is MUCH EASIER THAN THIS.....

So.......How DO we set the complete ball movement? With the ball in the starting position we have created a keyframe and the display looks a bit like this.......Note the position lines are horizontal....
Now we move the effects cursor line to the the end of the clip (right)
Re-position the ball in/over the basket. and set a second keyframe. The display looks a bit like this now....
The vertical position may have changed but that is not important since the basket is at a different height to the starting position
Now grab the green Position Vertical line somewhere in between the two keyframes and drag it downwards. It will form a smooth curve Its not setting a new keyframe but the line now represents the movement (position) of the ball in the vertical plane between the start position (keyframe 1 - the thrower's hand) and the end position (keyframe 2 - the basket) It's not a technically correct parabola but it's close enough.....

Playing the clip will show the ball leaving the players hand, arcing up and descending to hit the basket.

The lower the curve is dragged the higher the ball moves so you can control the height of the ball. By dragging the yellow marker left/right you can control the trajectory and the position of maximum height. The start and end positions remain unaltered as they are controlled by the keyframes. Here are some stills from the suggested setup...

If you want to only show a part of the movement (and set up questions regarding the result) you can split Video Track 2 before the ball reaches the basket (or not) and delete the section to the right of the split. The ball will then travel towards the target but disappear before it reaches it This means you could setup several trajectories (A;B;C;D etc.,) some where the ball misses in front of the basket and some where it overshoots...even some where the ball bounces off the basket edge! ..It also means that you can CHEAT!! B)

Nat

[deleted]

Here is a refinement on Borate's method which may be a bit quicker.....

Having created your single image animated ball as I described above, Export it to a folder on your PC as an Image Sequence....Don't forget to set the export format to PNG with Transparency. This will give you a file of quickly made png images each showing the successive positions of the ball, that you can use as Borate describes.

The number of images you end up with depends on the duration of the animation image. Which can be set in Options.

Reopen VP and set the Still Image Duration to 0.5 seconds. (its up to you)
Load all the png ball position images to the clip bin. They will be nicely numbered.
Drop them one at a time onto successive tracks lining the start each one up with then end of the previous one. If you ended up with a lot then use every other one...or every 5th one etc. A one second animated clip duration will give about 15 images. (and use around 17 tracks)
To finish, drag the ends out to make all the tracks the same length

The sequence should then play and the ball will appear every 0.5 seconds and remain in place until the clip ends.

Nat

borate

Nice. One further refinement, when overlaying the png transparent images onto the sequence use <ctrl-shift-page up>. Speedy.