Is this jump shot illegal?

depends

belmicah said:
Nice proof, but....
you have shown that it is possible for a ball to get over an impeding ball that is 1mm away yes, but it is IMPOSSIBLE for the cue ball to be struck only once, to move BACKWARDS (as seen in the screenshot), and then travel FORWARD without hitting the shaft or other part of the cue stick.
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I thtink you have to be careful drawing inferences from an encoded video. Lossy compressed video is not frame accurate and has all sorts of odd artifacts.

There is no "frame" in lossy compression. There are key frames and then the algorithm does magical things and encodes just changes (this can be done a few different ways depending on the particular codec).

The problem with no frame is that things do not move smoothly. If you own a tivo a good example of this is - pause it, go forward "frame" by "frame" then go in reverse, it will never just go back to the previous frame because it can't it has to skip all the way back to the last frame, so it jumps around.

This also means that sometimes one part of the frame (one object) may move while the rest stays static even if it is moving correctly.

When viewed at normal speed it seems fluid and physically correct, but when viewed "frame" by "frame" weird things happen.

I'm not saying that it does not hit the stick twice or move backwards, just that it is nearly impossible to tell from this video. Even if you had the original VHS tape it might not be so clear. That's why HSV is so important for analyzing these sorts of things...- then every frame is a single, clear picture.

I also don't think the cue moves backwards at all, that would seem to be impossible the cue stick is hitting the cue from behind, it would have to stick to the cue stick in some way to move backwards...

That goes back to the problem with mpeg type video, when you pause it and the ball and stick seem to overlap, it's really just an encoding artifact...

I also think that with the balls only 1mm apart that if the cue stick were staying in constant contact with the cue ball for even a very short time, it would push it into the object ball resulting in obvious object ball motion.

Anyone got an HSV camera to spare?:)
 
belmicah said:
Nice proof, but....
you have shown that it is possible for a ball to get over an impeding ball that is 1mm away yes, but it is IMPOSSIBLE for the cue ball to be struck only once, to move BACKWARDS (as seen in the screenshot), and then travel FORWARD without hitting the shaft or other part of the cue stick.
Click to expand...


I agree. This other video shows the same thing.

http://www.youtube.com/profile_videos?user=XtremeBilliard

Again, it's annoyingly difficult to freeze the frame right, but the trajectory shows the origin about a quarter inch or so away from the original cueball location.

Should we come up with a friendly wager on what the results of a highspeed camera will show? :D
 
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juggler314 said:
Definitely need high speed video, the guy that writes that column every month in one of the billiard mags has shown that even some masses that everyone would call routinely legal result in a double hit. I think that for reffing wise if you can't determine a double hit without HSV, it's good...unless it can be shown that it is impossible for the cue to move away from the ball fast enough...

-chris
Click to expand...
I could have sworn that AZBer Jorge Torres has this shot on high speed video/super slow motion.

Fred <~~~ I could be senile
 
I agree HSV would be nice, but I guarantee you will see that the cue ball spins backward violently, and then "rides" up the shaft until it is propelled forward.

Until further evidence, I am finished defending my argument and I encourage everyone to find proof of what is really happening here.

It just seems logical (and easily explainable) for me to conceptualize how much force is being exerted on the cueball and the vectors of these forces that combine into a forward moving parabola. The forces being exerted by shear contact with the cueball (throwing out rolling/sliding friction "spin") do not add up to produce the desired forward parabolic movement.

Imagine if you will, the cueball being frozen to a rail, and is struck with high follow with great force. Will the cue ball roll up the rail into the air? Undoubtedly. Why then is it so hard to imagine, that the cue ball being struck here with extreme draw (exactly opposite the high on the rail) will move in that particular direction (perpendicular to the angle of the cue)?
 
It's a leagal shot, I can do that shot with a regular jump cue. But if you just use the shaft it makes that shot alot easier.
 
This is a type of miscue and if an intentional miscue is a foul then this is a foul.

I would allow Larry to play the shot and I'm sure he would allow it for me by our rules... If I was in tournament play and the no intentional miscue rule is in effect, then I would want to object, but only because it's not my rules in a tournament. If you can't miscue on purpose then this is out, with the many other intentional miscue's that are taken out of the game.
 
I am working on the math of this shot. I am trying to figure out if it will spin backwards first, or if it actually just jumps over the impeding ball at an angle.

The hard part is that I don't know how much force is being exerted by the cue stick and how far from center he is hitting (looking from top down).

I think I can work this out if you guys bear with me.
 
From what I am seeing, Ppooler's shot looks like a bad hit, because the cue ball spins backward and is then propelled forward by the shaft.

But, Larry Nevel's shot looks like he used the rail a little to assist him in redirecting the cue ball forward, thus allowing him to get the cuestick out of the way like stated previously, by X breaker I believe, hitting it at 5:30 or so.

Two different shots here fellas.

One good hit, one bad...both amazing.

I have worked out all the math, and it comes down to be dependent on the frictional force in the -x direction. If that force is too big, the cue ball will spin backwards. If, however, the frictional force is small compared to the rebound force of the table on the ball, it CAN POSSIBLY clear an impeding ball that is not touching the cue ball.
 
belmicah, thanks for the compliment. I explained how I do it on page 3 of this thread. It's a below and off center hit so the shaft gets out of the way fast enough, and you're elevated at 90+, about 98 degrees (98.6? hehe). I'll see if I can film the shot this weekend in high quality and post a link. If this thread dies and I forget, remind me. lol
-yow!
 
I'm only commenting on the first video in this thread, and I didn't read the whole thread, but the shot Larry takes, is A. Perfectly legal, B. not any type of misscue (totally the opposite in fact), C. Not that difficult.

This shot can be done with a shaft quite easily, the "amazing" part is that it is done with an instrument longer and heavier than a shaft.

As for the angle, Larry is shooting this with a pretty much vertical stroke, but the cue is angled slightly towards the object ball, not away. This shot will not work if the cue is angled away from the object ball. It is this angle which produces the forward momentum.

Juggler314 is kind of on track regarding the video, but wrong in some ways as well. First of all, all 'video' is encoded. Most all video is also compressed, but not all. Video does have true frames. Key frames are used to mark events in video tracks, like start of scene, end of chapter, etc. AND used for interpolation by the codec. A high quality video codec is a quite a complex little bit of math. Some video codecs do a pixel by pixle comparison of each frame to aid in interlacing and de-interlacing. This can take quite a bit of computer horsepower, so most codecs aren't that accurate. The reason it is difficult to do frame by frame analysis, is that the "Frame Advance" control on most consumer electronics and software is not very sophisticated, and actually skips over several frames. There are 29 frames per second on high bitrate NTSC video, and going frame by frame would take too much time for most ordinary people, so the frame skip function on most devices cheats a little. Compression does cause weird artifacts on video, but also, YouTube is not truly video, it's Flash, and the conversion to Flash can cause even more artifacts, but neither are the prime cause of the way the video looks.

What causes the video to be difficult to decipher, is interlacing and de-interlacing. Non-HD NTSC video is interlaced. It means exactly what it sounds like, but here is a brief explanation.

To conserve bandwidth (bitrate), a single frame of video is only half of the picture. It is literally every other scan line of the video frame. Normal NTSC video has 525 scan lines, of which either 480 or 240 are used. These are the horizontal line across your TV set. For this video, the original was probably 240 scan lines. Each true frame only shows 120 of the lines. The next “frame” shows the alternate 120 lines. At 30 frames per second, your brain puts the two halves of each frame together. There are only 15 actual full frames per second in this video. HDTV by contrast has up to 1080 scan lines of resolution (currently), and can display them in interlaced or non-interlaced (progressive scan), format. Those $5000 1080P TVs that are so hot right now can display 1080 lines of horizontal video resolution at up to 60 full frames per second.

For an example of how interlacing can affect video quality, go see the thread by Eydie Romano about the stolen Cognoscenti cue. The pictures of the cue were obviously taken from a screen capture of a video, and are therefore interlaced. The pictures are two interlaced frames of the video, combined to form one non-interlaced (but interpolated), picture. The de-interlacing mechanism of the capture software used to take that picture, is not very high quality, so the interpolated "picture" still have plenty of evidence of the interlacing; i.e. the jaggies on the sides of the picture.

Interlacing and de-interlacing, which in video is done by a codec of varying quality, is the primary cause of this video being so difficult to freeze and see what is actually occurring.

If this video were shot with ultra high speed FILM (like 200FPS+), you would clearly see that there is no contact with the cueball and shaft, no backwards movement of the cueball, no contact with the cue ball and object ball, no miscue, no rail contact, and no tricks. I am very confident that this video is a legitimate and legal shot under the prevailing rules of the sport, and I am even more confident you will not be able to prove it either way with this as the source video. This video has gone through at least two compressions, and two interlace/de-interlace actions, and will never be accurate.
 
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SphinxnihpS said:
I'm only commenting on the first video in this thread, and I didn't read the whole thread, but the shot Larry takes, is A. Perfectly legal, B. not any type of misscue (totally the opposite in fact), C. Not that difficult.

If this video were shot with ultra high speed FILM (like 200FPS+), you would clearly see that there is no contact with the cueball and shaft, no backwards movement of the cueball, no contact with the cue ball and object ball, no miscue, no rail contact, and no tricks. I am very confident that this video is a legitimate and legal shot under the prevailing rules of the sport, and I am even more confident you will not be able to prove it either way with this as the source video. This video has gone through at least two compressions, and two interlace/de-interlace actions, and will never be accurate.
Click to expand...

Thanks for the lesson in video technology (not that we needed it), but look at the other video. It is a bad hit. I do agree that Nevel's is probably good though.

If this is so easy to do, and you are a master at video...then do it yourself and post a few frames from the HSV so you can prove it.
 
Jump Shot

Hey guys I was reading and thought I would chime in.

I frequently jump form anywhere from about 8mm down to my best at 3mm.

The shot is possible without being a foul.

Yow is correct when he say you shoot backwards to make it jump that close.

If you do that and hit it in the "sweet spot" it will compress the felt back from the origiinal resting position of the ball.

This allows the cue to jump from say........2-3mm away from the ball as a starting point. At the speed the cue is shot to be able to get a ball to jump that high that quick, the cue is thrown away from the ball.

My money is that it is legal.

You better freeze him to a ball if you wanna hook him.

Jason "The Michigan Kid" Lynch
 
belmicah said:
Thanks for the lesson in video technology (not that we needed it), but look at the other video. It is a bad hit. I do agree that Nevel's is probably good though.

If this is so easy to do, and you are a master at video...then do it yourself and post a few frames from the HSV so you can prove it.
Click to expand...

I would consider myself a student of video, not even close to a master. I don't even own a video camera outside the one in my cell phone. A high speed film camera is quite expensive. An HD video camera starts somewhere around a million bucks. Why don't you just take the shaft off of your cue, and practice the shot a few time. You could probably do it from within an inch of the object ball within your first several tries. You litterally throw the shaft at the edge of the ball, like a dart. These shots are all about stroke speed. Like I said, I didn't even watch the "other" video.
 
Sphinx,

Thanks for the video education. I suspected that relying on frame to frame images, from a YouTube video, to interpret events would be problematic.


Luxury,

I accidently found that pooler video while poking around at YouTube. He has three in the series. Be sure to see them all. Just realize, he may have used enough film to do Gone With the Wind, twice! These shots don't go down on the first try very often. Not knocking him at all. I thought his production was really entertaining. Many other observers seem to agree.
 
belmicah said:
From what I am seeing, Ppooler's shot looks like a bad hit, because the cue ball spins backward and is then propelled forward by the shaft.

But, Larry Nevel's shot looks like he used the rail a little to assist him in redirecting the cue ball forward, thus allowing him to get the cuestick out of the way like stated previously, by X breaker I believe, hitting it at 5:30 or so.

Two different shots here fellas.

One good hit, one bad...both amazing.
Click to expand...

Well, after another duel with the pause button I've gotten it right for Nevel's shot. So this has me agreeing with belmicah, one good hit, one bad. Hats off to Larry Nevel

Looks like a good hit to me. The cue ball appears to be travelling right along the appropriate parabola to get over that ball without a double hit.
 
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