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cbx
Swordmaster
Canada
296 Posts |
 Posted - Mar 31 2003 : 2:46:30 PM
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What the (explitive deleted) is a Quaternion any way? I understand the x,y,z part but what could the w possible be for? Mabe if someone explained it to me I might decide to start using it, since I have seen it kicking aroung since DirectX7.
Just thought I'd ask. |
Created by: X
http://www.createdbyx.com/ |
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Eric Coleman
Gladiator
USA
811 Posts |
Posted - Mar 31 2003 : 7:40:47 PM
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A quaternion is a complex number. It is of the form A + iB + jC + kD, where A,B,C,D are Real numbers. The imaginary numbers i,j,k are related such at i * i = j * j = k * k = -1, and i * j = k and j * i = -k. There are other variations, but this is the traditional Hamiltonian system.
A unit quaternion, its length = 1, represents a rotation in 3D cartesian space. For quaternions as related to game programming, you only work the unit quaternions. Quaternions have complex rules for mathematical operations, and often times a quaternion is represented as a grouping of a scalar and a vector. The scalar is the real coefficent, and the vector is the imaginary coefficients. It would look something like this, [A, (B,C,D)]. In most mathematical cases, the variable w is used as the real coefficient, and x,y,z are the coefficients for i,j,k respectively. The notation of a scalar and vector is used simply for ease of mathematical operations, because in this notation, some of the operations mirror traditional vector operations such as the Dot and Cross product. But in fact, quaternions were discovered long before vectors.
The use of a quaternion to transform a vector is simply the equation:
v' = qvq*
Where v' is the transformed vector caste to a quaternion, v is the original vector (also caste to a quaternion), and q and q* are the quaternion and its complex conjugate.
You might want to look at the quaternion info at http://www.gamedev.net/
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cbx
Swordmaster
Canada
296 Posts |
Posted - Apr 01 2003 : 12:12:10 AM
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Huh? What was that? In my best austin powers impression ... "ABbuuu".
What the hell kind of drugs are these mathmaticians on any way!
quote:
It is of the form A + iB + jC + kD, where A,B,C,D are Real numbers.
What???? A + Zg + coagulant divided by dog sniff, What the hell does that have to with anything.
That's worse then RHW ... quote:
reciprocal of homogeneous w from homogeneous coordinate (x,y,z,w).
???
I feel stupider having read that mumbo jumbo then I was before I asked the question.
I guess what i'm trying to say is SPEAK ENGLISH!
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http://www.createdbyx.com/ |
Edited by - cbx on Apr 01 2003 12:37:08 AM |
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cbx
Swordmaster
Canada
296 Posts |
Posted - Apr 01 2003 : 12:32:58 AM
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You know what! I'm not finished yet!
What the hell is the world comming to when we can't even stick to rotating a vector the 'natural' way.
And don't you sit there mister "Eric Coleman" and presume to tell me you know what any of that means, mister fancy schmancy cut and paste!
Huf Huf. ..
And a another thing, who the hell comes up with the names for those things anyway, Coefficent, Hamiltonian, Quaternion, reciprocal of homogeneous w! I'm getting balder with every fist full of hair!
Huf Huf Cough, Huf Huf ...
Dammit, if I ever run into that Hamiltonian guy in a dark allyway i'll hack him up and stuff him in a cooler so my parents don't see ...
Arrggg ... Chest getting tighter .... Extream pain ... Dam you Eric Coleman... dam you ... 
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cbx
Swordmaster
Canada
296 Posts |
Posted - Apr 01 2003 : 12:35:59 AM
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I'm alive! I'm alive! It's a miricle!
PS: My prev post was purly for entertainment value and comic relief. Or was it! Doum Doum Doum ... |
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Eric Coleman
Gladiator
USA
811 Posts |
Posted - Apr 01 2003 : 08:15:24 AM
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| If you don't understand something, then making fun of it doesn't add any credibility to you actually wanting to learn about it. You run the risk of no one wanting to answer your questions because of your childish posts. And for the record, I did not copy and paste anything. |
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cbx
Swordmaster
Canada
296 Posts |
Posted - Apr 01 2003 : 3:35:38 PM
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OK, fair enough. But I am still left with no answer to the question, "What is a Quaternion"?
As for me I am the type who only learns something if I need to or if I find myself interested in it. For example I have never taken an active interest in database programming. I know the absolute basics of it. But I am not going to start learning about it. Why? Because I have no need for it. It is far more easier/quicker/simpler for me to save data into a file format of my own then to spend time learning how to program against SQL for axample.
Now when I draw a comparison with my lack of database knowledge, to my lack of knoledge about Quaternions you begin to see where I'm comming from. I can rotate a 3d object using vectors and matricies etc. So why do I need to learn about Quaternions?
I suspect that this is a question that many people who read these forurm posts ask. Yes there is a place for the advanced mathmatics of Quaternions etc. But that leaves the rest of us scratching our heads.
By the way I have posed this Quaternion question in fourms and new groups before so I was expecting a responce like yours. A responce that I could ... ahem ... well, poke a little fun at. When you get it you get it. But when you don't you fell as intellegent as a chimp.
As childish as it may be, if describing what a Quaternion is, means you have to dum it down so a child could understand the basics of it, then I am that child. Just don't put mathatical equasions in front of me or speak in a mathmatical tounge, before you explain what a Quaternion is used for. Otherwise there will not be a base from which to understand the math behind it.
quote:
Originally posted by Eric Coleman
If you don't understand something, then making fun of it doesn't add any credibility to you actually wanting to learn about it. You run the risk of no one wanting to answer your questions because of your childish posts. And for the record, I did not copy and paste anything.
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Chris_Poskus
Neophyte
Canada
6 Posts |
Posted - Apr 01 2003 : 5:05:52 PM
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quote:
Originally posted by Eric Coleman
A quaternion is a complex number.
You might want to look at the quaternion info at http://www.gamedev.net/
Duh... :P |
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cbx
Swordmaster
Canada
296 Posts |
Posted - Apr 01 2003 : 7:47:07 PM
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OK, for starters I already kew about the game dev site. Second I have to thank you eric because I have found that dam page I was looking for, for the past 4 months. (PS: not a page about quaternions but the game company list page. )
Lastly. Yes I have and did look at the gamedev site. I looked thru all of the articles and beginers sections and i still have not seen anything on quaternions!
So not to push my luck with you any further and to save myself any more imbarrasment. Mabe, if you are willing to, post the url of the quaternion article you believe is on the gamedev site. 
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AT
Squire
18 Posts |
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cbx
Swordmaster
Canada
296 Posts |
Posted - Apr 01 2003 : 9:42:37 PM
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| Well you did not exactly specify to use an advanced google site search now did you! |
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cbx
Swordmaster
Canada
296 Posts |
Posted - Apr 01 2003 : 10:03:58 PM
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Whu Hoooooo! Vindication baby! Now that's what I'm talking about!
http://www.gamedev.net/reference/programming/features/whyquats/page4.asp
Check out the start of the third paragraph.
quote:
Software engineers, in general, are not mathematicians.
And check this out!
quote:
Quaternions lend themselves well to graduate projects and technical theses. They are very complicated, so describing them (and defending them) can take many words and many pages of formulas. Vectors, by comparison, are straightforward to the point of being boring.
I love boring! I say to hell with quaternions i'm sticking to my vectors and matricies all the way! Thanks Eric you've been a great help. I now know all i need to know about quaternoins.
And lets not forget this tidbit from the faq page.
quote:
7. Have you ever written any actual code? / Do you even know anything at all about mathematics?
A. I have been writing games professionally since 1987. I have a degree in mathematics.
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Edited by - cbx on Apr 01 2003 10:09:08 PM |
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AT
Squire
18 Posts |
Posted - Apr 01 2003 : 10:31:10 PM
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quote:
you did not exactly specify to use an advanced google site search
No, I said use the search box http://www.gamedev.net/reference/
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cbx
Swordmaster
Canada
296 Posts |
Posted - Apr 02 2003 : 03:03:55 AM
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hay your not Eric coleman. I mistook you for eric, that's why I said you did not say to use google.
quote:
Originally posted by AT
quote:
you did not exactly specify to use an advanced google site search
No, I said use the search box http://www.gamedev.net/reference/
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Eric Coleman
Gladiator
USA
811 Posts |
Posted - Apr 02 2003 : 12:01:23 PM
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AT, I fixed that big long URL you posted. It seems the google url causes the forum's automatic url recognition to go crazy. The url works now 
cbx, if you look at the "articles and reference" section at Gamedev.net, you would have found the quaternion information. Here is a link to the quaternion articles. gamedev quaternion link
As for quoting the Diana Gruber article, you have been mislead. Diana Gruber doesn't know a damn thing about quaternions, and her article has been removed from the GameDev.net quaternion section because it is full of wrong information. If you look at the first page of that article, click here, you will see Gamedev.net's disclaimer.
As a final note, quaternions are not necessary for a 3D game. You can use any method of rotation you want, either Euler angles, Axis angle, spherical angles, etc. |
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cbx
Swordmaster
Canada
296 Posts |
Posted - Apr 02 2003 : 2:40:39 PM
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No eric, no! Your runining it for me! I thought I was done with those dam quaternions, then you come along and debunk her article. Arrraahhh! Why could you not leave me to my blissfull ignorence! 
As for why I am sticking to my vectors and matricies any way? Because I use Direct3D to render my graphics. And it does not matter what kind of math you use to do rotations it all gets converted and stored into a matrix. And it gets storted in a matrix because that is the only relavent data type that the direct3d pipline is designed for. Weather you use quaternions or vectors for rotations, the results all get stored inside of a matrix! |
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http://www.createdbyx.com/ |
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What the (explitive deleted) is a Quaternion?
