The TRIANGULATOR 5000
Well, not really that fancy.
To use: Input 3 note names with their octaves (C4 for middle C, etc.) I’ve only tested it with the fields going from lowest to highest note, but you’re welcome to see what happens if other things are done. Click on “Show Chord Things” and two lines will rotate to form a triangle. There’s still line bits that come out the ends and I’m sure this won’t work for everything, and it’s limited to 3 voices, but not too bad given my rustiness with trig and continued brainfog.
Enjoy!