FFMpeg Transitions -- Part 4

The past few posts have been focusing on dynamic filter transition effects.  This post will bookend this series.  Let's finish up.

Circular Transitions

Let's dust off our high school geometry notes; we can calculate the distance from position (x,y) from the center of the image (W/2, H/2) using the following:

If we compare this distance to a linearly increasing range, based on time we can apply a increasing/decreasing circular boundary.  In this case, we are utilizing max(W,H) to ensure the circular geometry finalizes with the dimensions of the video (width and/or height);

$ ffmpeg -i image02.mp4 -i image01.mp4 -filter_complex "[0:v][1:v]blend=all_expr='if(gte(sqrt((X-W/2)*(X-W/2)+(H/2-Y)*(H/2-Y)),(T/1*max(W,H))),A,B)'" circleOpen.mp4

$ ffmpeg -i image01.mp4 -i image02.mp4 -filter_complex "[0:v][1:v]blend=all_expr='if(lte(sqrt((X-W/2)*(X-W/2)+(H/2-Y)*(H/2-Y)),(max(W,H)-(T/1*max(W,H)))),A,B)'" circleClose.mp4

Expanding Rectangular Window

Compounding on the horizontal and vertical opening effects we can get an expanding window effect;

$ ffmpeg -i image02.mp4 -i image01.mp4 -filter_complex "[0:v][1:v]blend=all_expr='if(between(X,(W/2-T/1*W/2),(W/2+T/1*W/2))*between(Y,(H/2-T/1*H/2),(H/2+T/1*H/2)),B,A)'" expandingWindow.mp4

While there are countless other possible effects, this is a decent crack at a representative sampling of such effects.

Whelp, that's it; the knowledge bank is empty.  Hope you found this series of posts of some value, perhaps just a momentary read from your palace of solitude.

Cheers.