Pubo
Active member
wow, thank you so much for this!
Dr.Dave's 30 degree rule visualized
- Thread starter Pubo
- Start date
On an unrelated note I was unaware of how much I had been using light reflection on the object balls for aiming until I played under a set of square lights like Predators, the reflections are far different.
Pubo
Active member
Yeah the ring light makes circular square reflection on the ball instead of a single strip
That one is quite simple. If you shoot the cue ball through any spot on the front of the ball, it should drive through parallel to the line from the center of the object ball exiting through the aiming point. Note, you aim and shoot directly at the point. All carom exits are speed sensitive so start at rolling speed like in your 30 degree video.
Pubo
Active member
I think I know what you are saying now. So if you aim at some point in the front of OB and shoot the CB towards that point, then the final path of CB is parallel to the line connecting OB's center and the front point?
Yes to a degree. Like I said it's all speed sensitive. I can't find the book I first read it in nor do I remember the title/author - some green hard cover book on billiards and pool. Anyway if you use the method to make actual billiards, you need to change the aim spot to accommodate the displacement of the cue ball.
Another way to say it is:
- aim the OB in the direction you want the CB to go after contact, note that aimline's "exit" point on the OB's opposite side
- aim the CB through the OB at the OB's aimline "exit" point on its opposite side
- hit it with slow/medium follow
pj
chgo
Pubo
Active member
so this only works when your exit point is actually on the opposite side of OB, if your cut is thinner than half ball then the exit point doesn't exist?
Right - but you typically only use this technique when it doesn't matter where the OB goes, only where the CB caroms to (such as caroming to make a hanger or to get safe).
pj
chgo
I've thought about it; reasoning there's a way to extend the front of the ball sideways whether it be a straight line or some kind of triangle or arc - perhaps a circular orbit, but as you run out of ball, the tangent line starts to blend in and into its own strength as a viable aiming reference. And that's about as far as I got with it. I must say though, front of the ball aiming isn't as unpredictable as PJ would have you think. Repetition always works in areas requiring feel and judgement.
The video is excellent. I love the automatic ball-path tracking, and the protractor overlay is a nice touch. FYI, I’ve add the video at the bottom on the 30 degree rule resource page.
For those interested, more accurate equations, plots, and example ball-hit-fraction numbers, taking into account ball friction and inelasticity can be found here:
Yes my thoughts too.
Possible product trajectory: synchronous infrared / ultraviolet strobe light and camera with appropriate lens filter, to use bright spots to target accurate Hough circle transform and ball identification, in real time.
Oh about 40 or so.
This system works fairly well only for full hits. For more info, including a demonstration, see:
I was hoping one of you guys would add more detail. I think front of ball is correct though.
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From the shooter's perspective, the aim point is on the "back" side of the OB, on the side you can't see (behind the OB). Regardless, people have called this system "back of the ball aiming" for a long time.
The object ball moves forward, therefore the aiming point is on the front of the ball.
after you translate the link into English a pool player speaks
i believe it translate into
" a rolling-CB shot, over a wide range of cut angles, between a 1/4-ball hit (49 degree cut) and 3/4-ball hit (14 degree cut), the CB will deflect or carom off by very close to 30° (the “natural angle“) from its original direction after hitting the OB."
