That picture of the rifle point up is a good description to show that projectile do not defy gravity. You simply point slightly up and then it starts to fall once it leaves the muzzle. That was one of the hardest things I had to overcome teaching soldiers marksmanship in the Army.
I do it the old fashioned way myself. I figure it's good shooting practice as well.
Sometimes I like to do it all on one sheet of paper and just move the paper to each target location. Gives me a better visual of what's going on, kinda like a diagram of the arc of the pellet path on paper with the pellet holes.
Nice tutorial for beginners. Main reason I prefer FFP scopes over SFP as I don't have to do even more extra calculations when ranging a target @ various magnifications.