| --- Log opened Tue Jun 29 00:00:37 2010 |
| --- Day changed Tue Jun 29 2010 |
| 00:00 | | Orthia [orthianz@Nightstar-661d35aa.xnet.co.nz] has quit [Ping timeout: 121 seconds] |
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| 00:13 | < ASCII> | hey, can anyone point me towards a good reference for vectors, and movement along them? |
| 00:14 | < ASCII> | it seems like there's a lot of information, so I'm a bit at a loss as to where to start |
| 00:15 | <@McMartin> | Hmmm |
| 00:15 | <@McMartin> | A basic linear algebra text, quite possibly. |
| 00:16 | <@McMartin> | I had a decent one back in the day, but I'd have to track down the proper references for it. |
| 00:17 | < ASCII> | I have a feeling that what I want to do will be pretty simple once i find the right qurestion to ask |
| 00:17 | < ASCII> | since my software will handle vector math for me, I mostly need to figure out what i need to do |
| 00:20 | < Vornicus> | Describe your problem. Many of us have done this sort of thing. |
| 00:23 | < Vornicus> | actualyl I have to Store, so I'll be back in like half an hour. |
| 00:24 | < ASCII> | I have a rotation (h,p,b) a location (x,y,z), and a velocity (a) I need to translate the location along the rotated direction at the given speed |
| 00:24 | < Vornicus> | Aha! |
| 00:25 | < Vornicus> | So you want a constant-speed rotation, like somebody's driving a car, right? |
| 00:25 | < ASCII> | correct |
| 00:25 | < Vornicus> | in a straight line around the world that is |
| 00:26 | < Vornicus> | Hokay, let's see, how would I do this. |
| 00:26 | < ASCII> | no, the rotation could varry between sampling |
| 00:26 | < Vornicus> | Well, okay, but still, you need to figure out... |
| 00:26 | < ASCII> | yes |
| 00:28 | < Vornicus> | You can, using Euler Angles (I think that's the tool) the axis of rotation. |
| 00:28 | < ASCII> | I'm honestly undecided whether it would be easier to plot the path externally and just import the keyframes |
| 00:31 | < Vornicus> | Er, get, the axis of rotaton, and the angular velocity of that rotation. Then given the axis of rotation and the amount of rotation (length/radius = angle in radians) you can generate the matrix of rotation, and apply that to the vector. |
| 00:32 | < Vornicus> | I'm enough out of practice that I don't remember if there's a nicer way. |
| 00:34 | < ASCII> | this is gonna be a bitch |
| 00:48 | <@McMartin> | Note that for full 3-D rotation like a homing missile or something you want to avoid talking about angles directly because you'll run into an odd phenomenon called "gimbal lock" |
| 00:49 | <@McMartin> | For "like someone driving a car" that should not come up. |
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| 00:50 | < ASCII> | yes, I'm well aquainted with gimbol lock but I plan to be limiting this to a 2d plane |
| 00:51 | < ASCII> | I already wrote a node group to handle vertical motion |
| 00:53 | | * gnolam still can't really figure out what it is you want. |
| 00:53 | < gnolam> | Can you draw a diagram? |
| 01:01 | < Vornicus> | Okay, got it. To find the axis of rotation, apply the rotation you have... twice. This gives you the original point and two more points. Cross two differences between these points and you get the AoR |
| 01:03 | < gnolam> | Err... |
| 01:03 | | * gnolam reads the question again. |
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| 01:05 | < gnolam> | From "Translate the location along the rotated direction at the given speed" it just sounds like... l = l + s*r, where r is the rectangular representation of the originally spherical rotation vector. |
| 01:12 | < ASCII> | gnolam- ok, say I have an object sitting at 0,0,0 and facing a given direction. I need to move the object in that direction |
| 01:12 | < Vornicus> | AHa! |
| 01:12 | < ASCII> | in my case, it will only be rotating on one axis |
| 01:12 | < Vornicus> | Okay, my description was wrong. |
| 01:13 | < gnolam> | Then it really is as simple as position vector = position vector + lambda*direction vector. :) |
| 01:13 | < Vornicus> | gnolam has it. |
| 01:15 | < gnolam> | As for the direction vector's rectangular coordinates, they will depend on your coordinate system. |
| 01:15 | < Vornicus> | apply pitch then yaw; roll doesn't come into this calculation. |
| 01:16 | < gnolam> | You're thinking of the rotation now and not the translation. |
| 01:17 | < ASCII> | why yaw? |
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| 01:18 | < ASCII> | and also, when you say simple remember that you're dealing with someone who has no clue whatsoever how to derive lambda |
| 01:19 | < gnolam> | Lambda there is your speed. |
| 01:19 | < ASCII> | the coordinate system is cartesian |
| 01:20 | < Vornicus> | ASCII: okay. 1. what direction is +x? +y? +z? |
| 01:20 | < Vornicus> | (actually lambda is your speed times the amount of time between calculations.) |
| 01:20 | < gnolam> | For a vector v = (x, y, z), lambda*v = (lambda*x, lambda*y, lambda*z) (where lambda is a scalar, a real number) |
| 01:21 | < gnolam> | Well, yeah. |
| 01:21 | < gnolam> | But I'm game damaged. I think "speed per timestep", heh. |
| 01:21 | < Vornicus> | For positive pitch, do you point up, or down? For positive yaw, do you turn left or right? |
| 01:21 | < ASCII> | +x is right, +y is up, and +z is forward |
| 01:21 | < gnolam> | Left-handed coordinate system then. |
| 01:21 | < Vornicus> | For yaw 0, which way do you want to progress? |
| 01:21 | < ASCII> | +z |
| 01:22 | < Vornicus> | Okay, and the pitch/yaw questions, and then we'll have everything we need. |
| 01:22 | < ASCII> | with 0,0,0 rotation the object points along +z |
| 01:23 | < gnolam> | You still need to answer this one: <Vornicus> For positive pitch, do you point up, or down? For positive yaw, do you turn left or right? |
| 01:24 | < ASCII> | positive pitch is down |
| 01:25 | < ASCII> | and positive yaw is right |
| 01:25 | < Vornicus> | Okay, that's all I need. Let's see. |
| 01:26 | < ASCII> | though for lightwave I should point out that what you call pitch is 'heading' and what you call 'yaw' is 'pitch' |
| 01:26 | < Vornicus> | <0,0,1> ... <0, -sin(phi), cos(phi)> ... <sin(theta)*cos(phi), -sin(phi), cos(theta)*cos(phi)> |
| 01:26 | < ASCII> | er, the opposite |
| 01:26 | < ASCII> | rather |
| 01:26 | < Vornicus> | That last is your direction vector. |
| 01:26 | < ASCII> | yaw is heading, and pitch is pitch |
| 01:27 | < Vornicus> | Yeah, heading and yaw are the same thing |
| 01:27 | < Vornicus> | Or approximately |
| 01:27 | < ASCII> | hrm |
| 01:27 | < ASCII> | so how do I apply this |
| 01:27 | < Vornicus> | Your roll doesn't affect your actual direction vector. |
| 01:28 | < gnolam> | Vector addition is simple. Just add the components together. |
| 01:28 | < Vornicus> | and vector * scalar is also simple: multiply each component by the scalar. |
| 01:28 | < Vornicus> | Your speed/distance thing here is a scalar) |
| 01:29 | < gnolam> | u = (x, y, z), v = (r, s, t). u + v = (x + r, y + s, z + t) |
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| 01:30 | < gnolam> | Oh, and one more thing: make sure the angle format is the one whatever you're using is expecting (so you don't use degrees where it should be radians or vice versa). |
| 01:38 | < ASCII> | hrm |
| 01:42 | < ASCII> | oh, and i missed before, +x is right, +y is up, and +z is forward |
| 01:43 | < Vornicus> | You said that. |
| 01:45 | < ASCII> | ok, what is r,s,t |
| 01:47 | < gnolam> | The components of vector v in an example of vector addition. |
| 01:48 | < ASCII> | ok |
| 01:48 | < ASCII> | but like I said, I can add the vectors already |
| 01:49 | < ASCII> | I need to figure out the numbers to plug into them |
| 01:50 | < gnolam> | The direction vector is (sin(yaw)*cos(pitch), -sin(pitch), cos(yaw)*cos(pitch)) . |
| 01:51 | < ASCII> | ah |
| 01:51 | < Vornicus> | your starting position vector is whatever your position vector happens to be. Your distance is speed * per-tick time. |
| 01:53 | < Vornicus> | Then you just do new_pos = old_pos + distance * direction |
| 01:54 | < ASCII> | it boggles the mond that nobody has done something like this before |
| 01:54 | < ASCII> | *mind |
| 01:55 | < gnolam> | ? |
| 01:56 | < ASCII> | eh? just wondering why nobody's made something of this sort before |
| 01:56 | < gnolam> | Plenty of people have? |
| 01:57 | <@McMartin> | This is like every 3D engine ever |
| 01:57 | < ASCII> | ...I meant in lightwave |
| 01:57 | < ASCII> | That's WHY I thought it was odd, given it's ubiquity elsewhere |
| 01:58 | < gnolam> | BTW, for a moment there, before reading the correction or even the rest of the sentence, I thought you actually meant "It boggles the MOND". I thought "Whoa, the guy is attempting to replicate alternative physics theories but doesn't know his linear algebra?", heh. |
| 01:59 | < gnolam> | This is probably a sign that I should go to bed. |
| 02:01 | < ASCII> | heh |
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| 12:02 | < gnolam> | Argh. |
| 12:03 | < gnolam> | Anyone have any experience in setting up SVN on Windows? |
| 12:03 | < gnolam> | A server that is. Not a client. |
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| 13:26 | <@ToxicFrog> | gnolam: no, but based on my experience setting one up on linux, you'll be saving yourself a shitload of time and effort by using a DVCS instead. |
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| --- Log closed Tue Jun 29 14:21:08 2010 |
| --- Log opened Tue Jun 29 14:21:47 2010 |
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| 14:46 | < gnolam> | ToxicFrog: I have an existing revision history that I would like to keep. |
| 14:47 | <@ToxicFrog> | I stand by my statement, as my experience has been that converting an SVN depot to git (can't speak for other DVCSs) is still easier than setting up a new SVN server. |
| 14:57 | < gnolam> | Git is out. Last I checked, even the official builds said they were broken. |
| 14:59 | < gnolam> | And Mercurial seems to assume an up-and-running SVN server, which leads me back to question 1. |
| 15:00 | < gnolam> | ... so does Git, by the look of it. |
| 15:05 | < gnolam> | So it's doubly out. |
| 15:13 | | Orth is now known as Reiv |
| 15:30 | < jerith> | svn on Windows is not recommended by the svn people. |
| 15:31 | < gnolam> | I'm not planning on getting another computer soon, so it will have to do anyway. :P |
| 15:39 | <@ToxicFrog> | "broken" in what way? |
| 15:40 | <@ToxicFrog> | (also, I didn't realize you had a history without a server) |
| 15:41 | < jerith> | What form is the history in? |
| 15:45 | < gnolam> | I have a .tgz dump of the repo directory. |
| 15:54 | < jerith> | Ah. You're almost certainly going to need a *nix box to use that. |
| 15:55 | < jerith> | I can set one up for you on my webserver, if you like. |
| 15:55 | < jerith> | You'll just have to put the tarball somewhere I can get at it. |
| 15:55 | < jerith> | Then you can migrate it to hg or whatever. |
| 16:02 | | * PinkFreud pokes google with a sharp stick |
| 16:02 | < PinkFreud> | kindly release an imap client which doesn't crash on whitespace. kthx,bye |
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| 16:56 | < gnolam> | jerith: Thanks. |
| 16:57 | < gnolam> | I guess I'll try to get an SVN server working on little tank first, but if that doesn't work I'll contact you. |
| 16:57 | | * gnolam blarghs a bit more. |
| 16:57 | < jerith> | gnolam: I'm about to head out, but I'll be online again in a few hours. |
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| 19:27 | < Vornicus> | gnuh, need to name something. |
| 19:27 | < Stalker> | Hmmm? |
| 19:27 | <@ToxicFrog> | f3c306ed-9b4c-4e90-b9c3-925690a264fc |
| 19:27 | < Vornicus> | Not... quite useful there, tf |
| 19:28 | <@ToxicFrog> | ^.^ |
| 19:28 | < Vornicus> | I mean, okay, I grant it's /unique/, but that's about it. |
| 19:28 | < Vornicus> | Anyway: writing a logic puzzle thingy. |
| 19:29 | < Vornicus> | I need a function that tells me whether a particular value /is/ in a particular slot, and another function that tells me whether a particular value /can be/ in a particular slot. |
| 19:31 | <@ToxicFrog> | slot contains value, slot accepts value |
| 19:32 | < Vornicus> | Woot, thank you |
| 19:32 | < Vornicus> | I was having trouble because "is" is a keyword |
| 19:40 | < jerith> | Vornicus: Python? |
| 19:44 | < Vornicus> | yah |
| 20:12 | <@ToxicFrog> | Ok. |
| 20:12 | <@ToxicFrog> | Scala's parser combinators are the bomb. |
| 20:15 | <@McMartin> | Parser combinators generally rock entire sock drawers. |
| 20:18 | <@ToxicFrog> | I have a parser for a restricted subset of C (specifically, a file containing lots of array-of-struct declarations + some other code I don't care about and pass through verbatim) in 50 lines, which includes the AST classes. |
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| 20:30 | <@McMartin> | Sounds about right. |
| 20:30 | <@McMartin> | (I had similar experiences with Haskell's parser combinator library Parsec.) |
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| 20:58 | | * ToxicFrog nods |
| 20:58 | <@ToxicFrog> | I've heard good things about Parsec. |
| 20:59 | < jerith> | It's what pyparsing and such would very much like to be. |
| 20:59 | <@ToxicFrog> | scala.util.parsing.combinator is particularly nice because as long as you're inside a subclass of Parser, you have a bunch of implicit converters in scope, so things like: |
| 20:59 | <@ToxicFrog> | ("{" ~ fields ~ "}") * |
| 20:59 | <@ToxicFrog> | Are equivalent to: |
| 21:00 | <@ToxicFrog> | literal("{").append(fields).append(literal("}")).repeated |
| 21:01 | <@McMartin> | Yeah. Parsec's (ab)use of Monad abbreviation syntax lets it do similar |
| 21:03 | <@ToxicFrog> | <3 explicit implicit converters |
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| --- Log closed Wed Jun 30 00:00:35 2010 |