Circle To Square in Material

I followed the next video to make a circle with nice particle effects around a capturable platform by my characters :

In some cases i have square shaped platforms and i would like to create the same effect with a square instead of a circle. How could I do that?

you just need to change the mask used for the opacity to one thats square. you can make one in any basic image editor. or you could attempt to create it though nodes as done in the video but im not sure how to make a square doing that.

Something like this should work.

That’s solve my issue! Thx a lot!!!

This also works, it’s much simpler, readable and probably has a better performance. The downside is that you need to use an external program.