dr_dave

01-01-2005, 11:03 AM

This question was originally posted at:

original question thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&Board=ccb&Number=172110&page =0&view=collapsed&sb=5&o=&vc=1). I am answering it here so others can see it and comment on it more easily.

<blockquote><font class="small">Quote dave9ball:</font><hr> I think the articles and web site are outstanding. My engineering is a little rusty, but I think the principles are great!

Your recent article discussed difficulty related to distance. I have used the following estimation for years. I am curious if it is close to valid. I take an object ball 1 diamond from the pocket and the cue ball 1 diamond from the OB to be a difficulty of 1. I multiply the Cue to OB distance by the OB to pocket distance to get a relative number. A shot with OB 2 diamonds from pocket and cue 3 diamonds from OB is difficulty 6 ( 6 times more difficult than a 1). It can be useful in shot selection as well as speed. I consider angle difficulty to be a function of the cosine of the shot angle. I think I got this from an old Bob Jewett article. <hr /></blockquote>

My November '04 through Fanuary '05 articles posted online (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html) show the results of all of my analyses, so you might be able to compare your method or any other method to my results by looking at the plots in the articles. Shot difficulty, assuming a center ball hit, is a complex function of distance from the OB to the pocket, angle of the OB to the pocket, distance between the CB and OB, cut angle, and shot speed. I take all of these factors into consideration in my articles and analyses (TP 3.4 through 3.8) (http://www.engr.colostate.edu/~dga/pool/technical_proofs/index.html). For a non center ball hit, the effects of English (deflection/squirt, curve/swerve, and throw) would also need to be considered in a thorough analysis.

As I explain in my articles, I don't think a totally analytical approach is very practical at the table. I think knowing and having an intuitive feel for the principles derived from the analysis results is what is important. I summarize all of the useful principles in my articles.

Concerning your cosine of the angle approach, straight-on shots are the least diffcult, and 90 degree cut angle shots are near impossible, and the difficulty does incease significantly as the cut angle increases (faster than a cosine function), but if the cosine understanding helps you in your game, that's all that matters.

original question thread (http://www.billiardsdigest.com/ccboard/showthreaded.php?Cat=&Board=ccb&Number=172110&page =0&view=collapsed&sb=5&o=&vc=1). I am answering it here so others can see it and comment on it more easily.

<blockquote><font class="small">Quote dave9ball:</font><hr> I think the articles and web site are outstanding. My engineering is a little rusty, but I think the principles are great!

Your recent article discussed difficulty related to distance. I have used the following estimation for years. I am curious if it is close to valid. I take an object ball 1 diamond from the pocket and the cue ball 1 diamond from the OB to be a difficulty of 1. I multiply the Cue to OB distance by the OB to pocket distance to get a relative number. A shot with OB 2 diamonds from pocket and cue 3 diamonds from OB is difficulty 6 ( 6 times more difficult than a 1). It can be useful in shot selection as well as speed. I consider angle difficulty to be a function of the cosine of the shot angle. I think I got this from an old Bob Jewett article. <hr /></blockquote>

My November '04 through Fanuary '05 articles posted online (http://www.engr.colostate.edu/~dga/pool/bd_articles/index.html) show the results of all of my analyses, so you might be able to compare your method or any other method to my results by looking at the plots in the articles. Shot difficulty, assuming a center ball hit, is a complex function of distance from the OB to the pocket, angle of the OB to the pocket, distance between the CB and OB, cut angle, and shot speed. I take all of these factors into consideration in my articles and analyses (TP 3.4 through 3.8) (http://www.engr.colostate.edu/~dga/pool/technical_proofs/index.html). For a non center ball hit, the effects of English (deflection/squirt, curve/swerve, and throw) would also need to be considered in a thorough analysis.

As I explain in my articles, I don't think a totally analytical approach is very practical at the table. I think knowing and having an intuitive feel for the principles derived from the analysis results is what is important. I summarize all of the useful principles in my articles.

Concerning your cosine of the angle approach, straight-on shots are the least diffcult, and 90 degree cut angle shots are near impossible, and the difficulty does incease significantly as the cut angle increases (faster than a cosine function), but if the cosine understanding helps you in your game, that's all that matters.