CGTalk Quantity of waves over a dist calculated by Dist+Vol, negating Speed? Kill me..
 01-09-2013, 07:07 PM #16 Duncan Expert   Duncan Brinsmead Principal Scientist Autodesk Canada   Join Date: Jun 2002 Posts: 2,975 Actually I think I get what he is after, and it is a little interesting. As wave moves the wave length must change in exact proportion to speed so if the waves slow down (for example due to entering shallow water) then the wave length will be proportionately shorter. The result is that number of waves that pass by a fixed point during a time interval stays constant, which is not intuitive(but mathematically quite trivial). If the waves slow down 2X the wavelength is 1/2 what it was and thus the waves/sec is constant. Duncan share quote
01-09-2013, 10:35 PM   #17
cojam
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 Originally Posted by dudeman38 I'm only trying to debate the basic maths here, Forget all the dynamics of waves here, we're talking the basic maths, nothing more.

dudeman, the ACTUAL maths, she not so simple. You really need to understand partial differential equations and assumptions made and the extensions made and whats integrable, search for ... "water waves partial differential equations",

http://en.wikipedia.org/wiki/Kortew..._Vries_equation
http://en.wikipedia.org/wiki/Boussi...8water_waves%29
http://en.wikipedia.org/wiki/Nonlin...dinger_equation

gives you a taste. Hope it helps.

Last edited by cojam : 01-09-2013 at 11:04 PM.

01-09-2013, 11:15 PM   #18
Kanga
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Quote:
 Originally Posted by playmesumch00ns Is this the most stupid thread ever on here? This guy has to be trolling.

And yet:
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01-09-2013, 11:34 PM   #19
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 Originally Posted by Kanga

My VFX person used to tell me a cloth sim could do anything....
But I didn't expect that.
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01-09-2013, 11:51 PM   #20
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Quote:
 Originally Posted by CGIPadawan But I didn't expect that.

Yeah those are the sexiest waves I have ever seen, at least artificial ones that is.
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01-09-2013, 11:58 PM   #21
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 Originally Posted by cojam dudeman, the ACTUAL maths, she not so simple. You really need to understand partial differential equations and assumptions made and the extensions made and whats integrable, search for ... "water waves partial differential equations", http://en.wikipedia.org/wiki/Kortew..._Vries_equation http://en.wikipedia.org/wiki/Boussi...8water_waves%29 http://en.wikipedia.org/wiki/Nonlin...dinger_equation gives you a taste. Hope it helps.

For this problem, you only need the formula that Martin posted:

wavelength X frequency = speed

As Duncan said, if the speed is halved and the wavelength is also halved, then the frequency remains the same.

Think of people marching in single file onto a slow moving sidewalk. When one person steps on, the person behind is still moving at the original speed and starts to catch up. By the time the second person steps onto the sidewalk, they are closer together but also both moving proportionally more slowly. When the first person steps off the other end, he speeds up until by the time the second person steps off, they're back at the original distance apart and moving at the original speed. The number of people passing any point per second is the same before and after the sidewalk, right at the start and end of the sidewalk, and therefore also all along the sidewalk -- you can't have it any other way without people appearing or disappearing.

01-10-2013, 12:19 AM   #22
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 Think of people marching in single file onto a slow moving sidewalk...

Another example is a slow moving line of cars... if they reach a point at which they can then speed up they will spread out, such that the number of cars passing an observer each min. remains constant. It definitely seems counter intuitive that you don't have more cars moving by when they are able to speed up.

If during a day 1000 cars travel between two cities, then if you are positioned somewhere on the road you will see 1000 cars go by in the interval of a day, regardless of if you are at a slow bottleneck on the road or the autobahn.

 01-10-2013, 02:10 AM #23 dudeman38 Awesome portfolio Dudeman 3D Generalist/VFX Artist Australia   Join Date: Sep 2010 Posts: 159 Thank you Duncan and grahamef, this is exactly what I'm talking about!! =) The other repliers were driving me insane! The truth of this aspect of the problem is actually just this simple, and unaffected by the other dynamics they're trying to bring into the conversation, that was so irritating lol. Thanks for replying guys, it's made my day to finally get responses from people who see logic =) Your responses should be enough to help my client see the reality of his request here. One more thing, as my friend will likely believe his theory has not been debunked, can you also just write to confirm for him that increasing the volume of the waves at set points instead of the speed will not decrease or increase the wavelength without the speed being a part of that equation? I can't believe he thinks that the waves can be moving at a constant speed yet still become further apart or closer together.. but he does lol =/ Last edited by dudeman38 : 01-10-2013 at 03:06 AM. share quote
 01-10-2013, 02:28 AM #24 Artbot Mostly Harmless   portfolio Richard Green The Man Who Sold the World USA   Join Date: Dec 2001 Posts: 5,122 Since when is it CGS member's duty to convince your clients they are idiots? Dare I say that if your rudeness here is indicative of how you are speaking to your client, I think I know where the actual problem may be. __________________ www.artbot.com share quote
 01-10-2013, 03:07 AM #25 dudeman38 Awesome portfolio Dudeman 3D Generalist/VFX Artist Australia   Join Date: Sep 2010 Posts: 159 Manners waste time and restrict the flow of information, just like your post above, being completely off topic. I also have no comprehension of them nor care to have. share quote
01-10-2013, 03:49 AM   #26
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Quote:
 Originally Posted by dudeman38 Manners waste time and restrict the flow of information, just like your post above, being completely off topic. I also have no comprehension of them nor care to have.

Your manners will see you suffer a severe restriction to the flow of information from most member here I believe.
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Last edited by Kanga : 01-10-2013 at 05:32 AM.

01-10-2013, 04:16 AM   #27
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 Originally Posted by dudeman38 Manners waste time and restrict the flow of information, just like your post above, being completely off topic. I also have no comprehension of them nor care to have.

Manners do have their utility. You will find many arguments go smoother when taken up politely. Think of it as "noise removal" in your transmissions.
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01-10-2013, 09:37 AM   #28
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 Originally Posted by grahamef Think of people marching in single file onto a slow moving sidewalk. ....

I can see what your saying, but grahamef that's an analogy, not a mathematical proof. same for the equation you state that is derived from a mathematical proof defined elsewhere. As said by the op, he wanted proof, and the only way for this IS to understand the math. There is rigor in mathematics for this very reason, otherwise everyone would be selling analogies, those are called hypothesis. While a starting place they not the end. Otherwise we'd all still think the world is flat, wouldn't we.

If he wanted an analogy, or specifically a non-rigor based proof, I would have suggested that a a few hours playing with a simple ocean sim's would have clearly answered his own problem.

But after reading some of the op comments, and attitude, it's not surprising, he can master none of them.

Last edited by cojam : 01-10-2013 at 09:48 AM.

01-10-2013, 09:55 AM   #29
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 Originally Posted by dudeman38 Manners waste time and restrict the flow of information, just like your post above, being completely off topic. I also have no comprehension of them nor care to have.

When people state things like the above it's much more telling than any financial quote or interview can ever be, because it's a clear indication to any future employer who's hiring full-time or freelance, who often frequent here, just what they are letting themselves in for.

01-10-2013, 07:48 PM   #30
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 Originally Posted by cojam I can see what your saying, but grahamef that's an analogy, not a mathematical proof.

There is really not that much math required in this situation. If in 1 hour one has 100 waves moving from point A to point B then over the interval of 1 hour an observer at any point between A and B will count 100 waves going by, regardless of how slow or fast the waves are travelling at different points along the way. Dare I say QED?

It has nothing to do with the dynamics of waves ( I've written ocean wave solvers as well as shallow water solvers so I'm not ignorant on that count ).