Crooked Pro Pool Strokes in Video

[asbani]

Flawed understanding of putting a 2D line on top of a 3D image.

I agree with this completely, I even mentioned it in my previous post, it was so clear to me, perspective view understanding is clear to some, and not clear to others, it is one thing that you cannot learn.

I got a friend of mine who finds it difficult to draw a cube with its inside lines, some people are just not cut for this even though it's very easy.

 

[dr_dave]

For those interested, here are some additional comments from a Facebook discussion concerning NV J.36 – Crooked Pro Pool Strokes in Video:

Another issue at play is: Because of the low camera angle with Samm's shot, the projected length of the cue is very short so any small error (sideways motion of the tip) might seem exaggerated (in comparison to the small projected length of the cue).

We can sometimes resolve perspective issues through other visual "cues." For example, it is easy to see the Fedor jump-shot aim as straight because we can see his body and stance, much of the table, his entire cue, his bridge hand position, etc. This a lot of visual information that helps us see his 3D aim in the 2D picture. However, with the overhead view of Corey's jump shot, we can't see his body or stance or the entire cue (to judge the smaller projected length due to the elevation), so there are no visual "cues" to indicate his cue elevation or alignment. Our brains are clueless to figure out the 3D aim from such limited 2D image information.

Thanks to everybody who contributed to the discussion (here and on YouTube and Facebook),
Dave

 

[Hits 'em Hard]

I don't think I said Samm's stroke was straight. If I did, I was mistaken. It definitely was not straight with that particular shot. My point was that it is not as crooked as it might look in the video.

Here are the pertinent NOTEs from the YouTube video descriptions:

from NV J.33 – Top 10 Secrets of a Good Draw/Backspin/Screw-Back Shot:
When I watched this shot in person, I was standing right behind the camera and I don't remember her stroke being that crooked. I think I would have noticed if it was, and I would have asked her to shoot again with a straighter stroke. I think it looks crooked in the video partly due to perspective issues with the camera angle and pendulum swing. I have seen this effect is other videos also. Samm's aim might have been slightly off and she might have hit the CB slightly off center, but her stroke was not as crooked as it might have appeared in the video. Again camera perspective can create optical illusions since the vertical angle of the cue (up and down) is changing during the pendulum stroke.

from NV J.34 – Is this Stroke Crooked … or is it Parallax?:
NOTE: Samm's stroke looks more crooked than mine in the video for three reasons:
1.) The camera angle was slightly different (at a larger angle) with her shot.
2.) As I pointed out in the video, her arm is shorter, which increases the up and down motion of the cue with the pendulum stroke for a given stroke length. This increases the perspective/parallax effect.
3.) Her stroke was definitely not straight, but not by as much as the video suggests. The "apparent" crookedness is exaggerated by the perspective/parallax effect.

Further explanation of the perspective/parallax effect:
When the camera is not straight inline with the shot, the perceived direction the cue is pointing varies with cue elevation, as clearly demonstrated with the examples in the video. If one uses a pendulum stroke, with a fixed shoulder and elbow, the cue elevation changes during the stroke. Therefore, the perceived direction of the cue changes during the stroke. I can assure you the strokes in this video were straighter than they look (albeit, Samm's stroke was definitely not straight).


Actually, it is very possible to draw straight back with a crooked stroke (especially if the crookedness is after the hit, during the follow through). It is also possible to draw back crooked with a perfectly straight stroke (aimed in the wrong direction).

I actually took a drafting course in college many years ago. It was the last year it was taught before we switched over to computer drafting and modeling software. I learned a lot about perspective projections in that course. I drew many 3D-to-2D projections by hand. I really enjoyed that part of the course. So I probably know more about perspective and 3D-to-2D projections than many (if not most) people.

Regards,
Dave

A stroke doesn’t need to be crooked more than a couple millimeter or so to produce these effects you’re seeing. Simply put, a cue from the proper perspective could look entirely straight with no taper to it. Cues, from a near to far perspective behave in the exact opposite manner than typical object does strictly due to its taper. You are simply not allowing yourself to be wrong. On a straight in shot, the cue ball needs to come straight back or we can assume the shot was never lined up straight. So if Samm’s stroke is straight, then she was lined up crooked. And all this crap doesn’t matter.

 

[dr_dave]

On a straight in shot, the cue ball needs to come straight back or we can assume the shot was never lined up straight.

... or the stroke into the CB was crooked ... or the table is not level.

Regards,
Dave

 

[MitchDAZB]

Thanks for the link. That was an interesting read. However, many of the illusions I describe in my video are not due to this stuff. Instead they are due to perspective projection effects resulting from viewing the 3D world via 2D image images.

Regards,
Dave

Keep digging!

 

[Hits 'em Hard]

... or the stroke into the CB was crooked ... or the table is not level.

Regards,
Dave

Now you’re making excuses. In that shot Samm played, that is the whole point of this controversy. You’re telling me, her stroke didn’t look crooked in person. That she was lined up correctly, and that you’re table is level. Which one of those three things do you suspect went wrong? My money is on Samm not being lined up straight as we see a clear, and direct movement of the cue ball to the side.

You’ve argued yourself into a hole here. Please stop, allow yourself the humility of being wrong. It’s not camera wizardry that has people questioning things anymore. It’s us wondering why you are trying so hard to justify something that is plainly not the problem at work.

 

[dr_dave]

On a straight in shot, the cue ball needs to come straight back or we can assume the shot was never lined up straight.

... or the stroke into the CB was crooked ... or the table is not level.

Now you’re making excuses.

I wasn't making excuses. I was just providing additional possible causes for a straight draw shot not coming straight back. Aligning and hitting the CB off-center is another possible cause. Cheating the pocket is another possible cause.

In that shot Samm played, that is the whole point of this controversy. You’re telling me, her stroke didn’t look crooked in person.

What I said was: It looked much more crooked in video than I remembered it looking in person. If it had looked that crooked when I was filming, I definitely would have demanded that she do the shot over again.

That she was lined up correctly, and that you’re table is level. Which one of those three things do you suspect went wrong?

Based on the video, it is obvious that her stroke was not straight, but I suspect her aim was slightly off, and the cue tip was slightly off-center. My table also has slight roll-off on that side of the table toward the long rail. All of this, in addition to the perspective/parallax effects, contributed to making the stroke and result look as bad as it did in video.

Regards,
Dave

 

[Hits 'em Hard]

I wasn't making excuses. I was just providing additional possible causes for a straight draw shot not coming straight back. Aligning and hitting the CB off-center is another possible cause.

What I said was: It looked much more crooked in video than I remembered it looking in person. If it had looked that crooked when I was filming, I definitely would have demanded that she do the shot over again.

Based on the video, it is obvious that her stroke was not straight, but I suspect her aim was slightly off, and the cue tip was slightly off-center. My table also has slight roll-off on that side of the table toward the long rail. All of this, in addition to the perspective/parallax effects, contributed to making the stroke and result look as bad as it did in video.

Regards,
Dave

Not buying it. You screwed up, and rather than fixing the video with a reshoot you’ve decided to argue to over a month now. Instead now you’ve opened up a whole new can of worms. Now that you’re retired, are you going to take the time to fix your years of mistakes in your videos? Or you just going to keep arguing with bs statements and evidence? Because here’s the deal, if you’re table is off that bad. Then that shot of Samm’s wouldn’t be the other shot that’s performed that would roll off. Six inches to the side and six inches back? Excuses. Fix your methodology so this shit doesn’t happen again.