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From: <SHA...@ao...> - 2000-09-09 05:54:53
|
In a message dated 09/09/00 00:14:16 !!!First Boot!!!, Ste...@im... writes: << Don't wait until the next frame to recurse the rebound. In my collision detection I let the movement continue as far as is possible during the frame that the collision takes place so the frame displays only the results of the bouncing. What I see at creases is a smooth migration toward the center of the crease until the player is directly on the crease. >> Hi, What I do is only test collision on tri's which the player is not allowed to walk on i.e. by testing the normal->y component of the surface. Then, to determine the player's y position, I shoot a ray straight down and see which tri this hits and from that compute the y of where the player is standing. This stops wallowing around in creases :) and also cues which sounds to play for the players footsteps based on the texture type under the player. Does your algorithm also have the undesirable effect in a concave corner where two walls meet?? John. |
From: Jason Z. <zi...@n-...> - 2000-09-09 02:00:55
|
I guess I phrased that line poorly. It should have said, each frame I keep sliding the player recursively until he comes to a stop then flip the frame and do it again. Problem is, when the player is in a valley he will often come to a stop on alternate sides of the valley each frame, and thus kind of bounce back and forth. I can reduce this by including friction (which I intend to do anyway), but unless I put a LOT of friction he will oscillate. I'm assuming the oscillation will occur in corners of buildings too. Maybe I'm doing something simple wrong in my implementation? From people's replies it sounds like what I'm doing should work. Here is my code, maybe someone can spot something. It is fairly simple. Note it isn't actually recursive, but it should be the same effect. It originally was recursive but I found this easier to debug. ----------------------------- // do the initial collision with world, sphereCenter is player's location, // vel is his velocity, cInfo is a struct that contains collision info bool collided = terrain->CollideSphere(sphereCenter,3.0f,vel,&cInfo); // if no collision just move to destination if(!collided) sphereCenter += vel; // do collision response if we hit something while(collided) { // remember what our destination point would have been zVector3 dest = sphereCenter + vel; // Move to the nearest collision zVector3 V = vel; V.normalize(); V = V * (cInfo.dist - 0.01f); // cInfo.dist is distance to collision sphereCenter += V; // Determine the sliding plane zPlane sp; sp.normal = cInfo.point - sphereCenter;// cInfo.point is collision point sp.normal.normalize(); sp.dist = Dot(sp.normal,cInfo.point); // create ray starting at where we should have stopped and going in // direction of plane normal zPickRay r; r.origin = dest; r.dir = sp.normal; // intersect with plane to find out distance to new position on that plane sp.Intersect(r); zVector3 slidePlaneNormal = sp.normal * r.dist zVector3 newDestinationPoint = dest + slidePlaneNormal; // Generate the slide vector, which will become our new velocity vector // for the next iteration vel = newDestinationPoint - cInfo.point; // make sure this new mini-velocity doesn't collide with anything else collided = wState->Terrain()->CollideSphere(sphereCenter,3.0f,vel,&cInfo); // if no collision add slide velocity and break out if(!collided) sphereCenter += vel; } ----------------------------- And thats it. I then set the player's location to sphereCenter and its done. It works wonderfully for the most part, until you get stuck in a crease. Is there something I'm overlooking? - Jason Zisk - nFusion Interactive LLC ----- Original Message ----- From: Steve Wood <Ste...@im...> To: <gda...@li...> Sent: Friday, September 08, 2000 7:44 PM Subject: RE: [Algorithms] Simple player collision response problem > > -----Original Message----- > > From: Jason Zisk [mailto:zi...@n-...] > > Sent: Thursday, September 07, 2000 9:42 AM > > To: Algorithms List > > Subject: [Algorithms] Simple player collision response problem > > > > What I'm doing now is simply calculating a sliding plane > > based on the poly the player is hitting and sliding him > > along that with the remaining velocity after the initial > > collision. I do this recursively each frame against the > > environment until the velocity is so small I can just set > > it to zero. > > > > Don't wait until the next frame to recurse the rebound. In my collision > detection I let the movement continue as far as is possible during the frame > that the collision takes place so the frame displays only the results of the > bouncing. What I see at creases is a smooth migration toward the center of > the crease until the player is directly on the crease. > _______________________________________________ > GDAlgorithms-list mailing list > GDA...@li... > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list |
From: Steve W. <Ste...@im...> - 2000-09-08 23:48:51
|
> -----Original Message----- > From: Jason Zisk [mailto:zi...@n-...] > Sent: Thursday, September 07, 2000 9:42 AM > To: Algorithms List > Subject: [Algorithms] Simple player collision response problem > > What I'm doing now is simply calculating a sliding plane > based on the poly the player is hitting and sliding him > along that with the remaining velocity after the initial > collision. I do this recursively each frame against the > environment until the velocity is so small I can just set > it to zero. > Don't wait until the next frame to recurse the rebound. In my collision detection I let the movement continue as far as is possible during the frame that the collision takes place so the frame displays only the results of the bouncing. What I see at creases is a smooth migration toward the center of the crease until the player is directly on the crease. |
From: Tom H. <to...@3d...> - 2000-09-08 19:29:43
|
At 03:17 AM 9/8/2000, you wrote: >I want to put them up as a web page somewhere, ideally at Sourceforge where >the >list is hosted, but I couldn't contact Tom Hubina, and besides, I wanted to >check with >you guys if somebody would mind. Amazing. Someone can't reply to you within 24hrs and suddenly they cannot be contacted? My reply was going to be, "Make is searchable and have it get updated every time an email is sent out and I'll get behind it 100%, but digging through three years of archives by hand is not my idea of fun". I was gonna phrase it a bit nicer, but since you couldn't wait, well, there it is. Anyway ... do what you want with the archive. If you get it searchable I'll go through and do a bit of clean up on my archive (Eudora mailbox) which contains almost every email ever sent to this list (there's a gap for a couple of days from a mailbox error while I was in Canada a couple months back) and get that to you. SourceForge has their head up their ass and doesn't appear to want to help get their archives functional at all. I've been trying to talk to them about this stuff, but so far the only response I've been able to get as been: "As far as I know, we do not import old archives into Geocrawler at all. It's too much of a headache and can lead to disaster. As far as searchability, Geocrawler needs to be totally rewritten and that is somewhere on the radar, but I'm not sure where. Until then, it's got some real problems. " Needless to say I'm more than a little bit unhappy about this. I'm also swamped with work right now and I really don't have time to be dealing with this properly. Tom |
From: Stefano 'P. B. <pa...@in...> - 2000-09-08 18:30:23
|
Of course this has to be done on manually transformed vertex coords. Anyone knows how commercial quality engines (Q3,UnrealT,...) handle polygon sorting for alpha blending? Do they use underlying structures like bsp? thanks ----- Original Message ----- From: "Amit Bakshi" <am...@de...> To: <gda...@li...> Sent: Friday, September 08, 2000 4:18 AM Subject: Re: [Algorithms] Sorting polys > Bin-sorting works fine in general and it's quite fast. I find the average > of the z values for the triangles and bin them. You can even do it on > a per-object basis and use the center of the bounding box/sphere. > > ----- Original Message ----- > From: "Mark Wayland" <mwa...@to...> > To: <gda...@li...> > Sent: Thursday, September 07, 2000 7:33 PM > Subject: Re: [Algorithms] Sorting polys > > > > You could try using a hash table indexed on a quantized z-depth. > > Intersecting polys present a bit of a problem - perhaps a dynamic > > form of BSP with pooled nodes to avoid dynamic allocation overhead. > > > > Mark > > > > ----- Original Message ----- > > From: "Stefano 'Panda' Baraldi" <pa...@in...> > > To: "ALGORITHMS" <alg...@3d...> > > Sent: Friday, September 08, 2000 4:24 AM > > Subject: [Algorithms] Sorting polys > > > > > > > Hi, i need to sort polygons for alpha blended objects. > > > Can you point me to some resource to do that? > > > > > > thank you > > > > > > > > > _______________________________________________ > > > GDAlgorithms-list mailing list > > > GDA...@li... > > > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list > > > > _______________________________________________ > > GDAlgorithms-list mailing list > > GDA...@li... > > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list > > > > _______________________________________________ > GDAlgorithms-list mailing list > GDA...@li... > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list |
From: Jason Z. <zi...@n-...> - 2000-09-08 15:31:51
|
Sorry for being dull, but I don't get it. :) Could you go into a bit more detail? I've tried remembering the velocity from last frame and doing tests against that to stop the oscillating but every time I did that it also cancelled out some movement I did want. Thanks, - Jason Zisk - nFusion Interactive LLC ----- Original Message ----- From: <SHA...@ao...> To: <gda...@li...> Sent: Friday, September 08, 2000 9:19 AM Subject: Re: [Algorithms] Simple player collision response problem > In a message dated 07/09/00 17:15:05 !!!First Boot!!!, zi...@n-... > writes: > > << > What I'm doing now is simply calculating a sliding plane based on the poly > the player is hitting and sliding him along that with the remaining velocity > after the initial collision. I do this recursively each frame against the > environment until the velocity is so small I can just set it to zero. > >> > > Hi, > > What you need to do is do it recursively between frames not each frame > otherwise you will see these oscillations. > > John. > _______________________________________________ > GDAlgorithms-list mailing list > GDA...@li... > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list |
From: <SHA...@ao...> - 2000-09-08 13:19:49
|
In a message dated 07/09/00 17:15:05 !!!First Boot!!!, zi...@n-... writes: << What I'm doing now is simply calculating a sliding plane based on the poly the player is hitting and sliding him along that with the remaining velocity after the initial collision. I do this recursively each frame against the environment until the velocity is so small I can just set it to zero. >> Hi, What you need to do is do it recursively between frames not each frame otherwise you will see these oscillations. John. |
From: Nikolay S. <ni...@we...> - 2000-09-08 12:18:52
|
> Does anyone know of a good book or other reference that'd > explain various > aspects of generating random numbers to someone that's not so much > mathematically inclined? E.g. how to test whether a random number > generator is good etc? Try out Don Knuth's "The Art Of Computer Programming", second volume. There's a chapter exactly on that [as far as I remember from my statistics class in university, becomes foggy :-)] . Cheers, Niki |
From: Pierre T. <p.t...@wa...> - 2000-09-08 12:17:10
|
Wow. Well done Ivan, that's a very precious package! I may have some posts from 1999 on a backup CD (..hmm, almost all of them I guess). But they're saved as .mbx files, I think that's Outlook Express' compressed format. Not really sure how to read them back. Pierre ----- Original Message ----- From: Ivan-Assen Ivanov <as...@ha...> To: <gda...@li...> Sent: Friday, September 08, 2000 12:17 PM Subject: [Algorithms] list archives again > Hello list, > > I exported my 8-month archives for [Algorithms] from my stuffed Outlook > folders > massaged them with a bit of Perl and built a bunch of HTMLs + an index page. > The index page contains the subjects of all the threads, each HTML is all > the messages > in a thread listed by date. > I wanted to do a fancier tree-like structure, but less than 30% of the > messages carry > the required for this In-Reply-To headers and I don't have the time or > enthusiasm to > make a super-heuristic-AI "reply recognition". > I want to put them up as a web page somewhere, ideally at Sourceforge where > the > list is hosted, but I couldn't contact Tom Hubina, and besides, I wanted to > check with > you guys if somebody would mind. > You can download an archive of the entire thing (bzip2 over > zip-without-compression) > form NetDrive: > > http://www.netdrive.com/~ivanassen/MyPublicFiles > > (click on My Public Files in the left pane; the file is 3dgamedev.zip.bz2 - > about 2 MB) > > you can find bzip2 at http://sources.redhat.com/bzip2/ > > Feel free to suggest additional formatting of the messages (or to volunteer > to > do it yourself :-) ) If somebody has messages from before Feb 2000 in > Outlook [Express], > please contact me. (Or in some other "processable" format) > > Regards, > Assen > > _______________________________________________ > GDAlgorithms-list mailing list > GDA...@li... > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list |
From: Stephen J B. <sj...@li...> - 2000-09-08 12:15:07
|
On Thu, 7 Sep 2000, Akbar A. wrote: > >Evans&Sutherland > what happend to them? They are still doing all the things they ever used to do. They even make OpenGL graphics cards for the PC. http://www.es.com > i remember when there name used to be everywhere, > evans that sutherland this... are evans and sutherland still alive? I don't *think* so - but I could easily be wrong. ---- Science being insufficient - neither ancient protein species deficient. Steve Baker (817)619-2657 (Vox/Vox-Mail) L3Com/Link Simulation & Training (817)619-2466 (Fax) Work: sj...@li... http://www.link.com Home: sjb...@ai... http://web2.airmail.net/sjbaker1 |
From: Ashley R. <as...@di...> - 2000-09-08 12:07:54
|
Hi all.. There are two chapters of information on pseudo-random number generators in a book called "Applied Cryptography" by "Bruce Schneier". Explains a few methods for generating (almost) random sequences, mainly aimed at crypto, but useful none the less. It shows how to set up a random number generator with a specific and provable maximum period (number of iteration before it starts to repeat) and how to use these together to get better randomness. Note sure if that is of too much interest to you but there are some applications when this is cool (pixelated fade between images for instance, when you set the period to be the number of pixel and your guaranteed to cover all the screen eventually). Also highly recommend this book to anyone that has to do any security or cryptography etc for their game (eg networking code). It has C code for alot of the algorithms and easy to understand explanations for protocol and algorithms for all sorts of cool things. Ash. > -----Original Message----- > From: gda...@li... > [mailto:gda...@li...]On > Behalf Of Ismo > Kärkkäinen > Sent: Friday, 8 September 2000 6:50 PM > To: gda...@li... > Subject: Re: [Algorithms] Random Numbers > >> [...] > > Does anyone know of a good book or other reference that'd > explain various > aspects of generating random numbers to someone that's not so much > mathematically inclined? E.g. how to test whether a random number > generator is good etc? |
From: Ivan-Assen I. <as...@ha...> - 2000-09-08 10:16:56
|
Hello list, I exported my 8-month archives for [Algorithms] from my stuffed Outlook folders massaged them with a bit of Perl and built a bunch of HTMLs + an index page. The index page contains the subjects of all the threads, each HTML is all the messages in a thread listed by date. I wanted to do a fancier tree-like structure, but less than 30% of the messages carry the required for this In-Reply-To headers and I don't have the time or enthusiasm to make a super-heuristic-AI "reply recognition". I want to put them up as a web page somewhere, ideally at Sourceforge where the list is hosted, but I couldn't contact Tom Hubina, and besides, I wanted to check with you guys if somebody would mind. You can download an archive of the entire thing (bzip2 over zip-without-compression) form NetDrive: http://www.netdrive.com/~ivanassen/MyPublicFiles (click on My Public Files in the left pane; the file is 3dgamedev.zip.bz2 - about 2 MB) you can find bzip2 at http://sources.redhat.com/bzip2/ Feel free to suggest additional formatting of the messages (or to volunteer to do it yourself :-) ) If somebody has messages from before Feb 2000 in Outlook [Express], please contact me. (Or in some other "processable" format) Regards, Assen |
From: Robert D. <RD...@ac...> - 2000-09-08 09:43:30
|
> Does anyone know of a good book or other reference that'd > explain various > aspects of generating random numbers to someone that's not so much > mathematically inclined? E.g. how to test whether a random number > generator is good etc? No, but you need to be aware that there is no such thing as 'good' - there are some cases which are obviously 'bad', if say you can never get certain numbers or if the distribution is skewed, but even when this isn't the case, the way you are making use of the numbers will effect how 'good' the generator is. You will often find that random number generators create patterns, which can have a dramatic effect on your results. For example, if you take a typical psuedo random number generator and use its output as input to a random walk - for example doing : x += rand()-0.5; y += rand()-0.5; then in many cases you will notice a long term drift, which is quite slow. if on the other hand you are using integers, and you take the bottom few bits, you will get a much more marked drift. also, very often you can make your randomness appear to be much greater by using it more ... for example if you use the same random number generator for jiggling sprites, making AI decisions, and so on, then you will find they each appear more random, because any patterns are lost by something else using the values in between. finally if you really need to use several random numbers one after another, check the behaviour for that specific case as many times as you can, to ensure you know what its doing. Rob |
From: <ia...@cs...> - 2000-09-08 08:49:47
|
On Thu, 7 Sep 2000, Johan Hammes wrote: > Hi > > I need a random number sequence with Gauss distribution. Do you know of an > algorithm that can do this. I asume that rand() generates white noise. I've been using this: double dgauss() { return sqrt(-2 * log(drand())) * cos(6.283185307 * drand()); } drand() gives evenly distributed numbers. The other alternative is sum of n evenly distributed numbers, with n = 30 the result should have gaussian distribution. AFAIK. Search for "+random +number +gaussian +generator +source +code". Does anyone know of a good book or other reference that'd explain various aspects of generating random numbers to someone that's not so much mathematically inclined? E.g. how to test whether a random number generator is good etc? Ismo -------------------| M.Sc., Assistant | My ehticator machine must've had a built-in moral Dept. of CS | compromise spectral release phantasmatron! I'm a Univ. of Joensuu | genius! ia...@cs... | -- Calvin Tel:(013)251 5329 | GSM: 040 774 3722 | |
From: Johan H. <jh...@mw...> - 2000-09-08 07:56:27
|
Hi I need a random number sequence with Gauss distribution. Do you know of an algorithm that can do this. I asume that rand() generates white noise. Johan Hammes |
From: Dave E. <eb...@ma...> - 2000-09-08 05:03:21
|
From: "Pierre Terdiman" <p.t...@wa...> > It would be interesting, yes... Another source for SVD is my code MgcMatrix3.* at the MgcCore.html page. This implements the algorithm from Golub's book (mentioned in this thread). For the original poster, if your matrix was computed as a sequence of matrices, each having translation, rotation, and a uniform scale, then the final product must also have only uniform scale. As someone else pointed out in this thread, in this case you can just look at the length of the first column of the 3x3 portion of the homogeneous matrix to get the scale, then normalize the three columns. You should then have a rotation matrix. -- Dave Eberly eb...@ma... http://www.magic-software.com |
From: Amit B. <am...@de...> - 2000-09-08 02:17:48
|
Bin-sorting works fine in general and it's quite fast. I find the average of the z values for the triangles and bin them. You can even do it on a per-object basis and use the center of the bounding box/sphere. ----- Original Message ----- From: "Mark Wayland" <mwa...@to...> To: <gda...@li...> Sent: Thursday, September 07, 2000 7:33 PM Subject: Re: [Algorithms] Sorting polys > You could try using a hash table indexed on a quantized z-depth. > Intersecting polys present a bit of a problem - perhaps a dynamic > form of BSP with pooled nodes to avoid dynamic allocation overhead. > > Mark > > ----- Original Message ----- > From: "Stefano 'Panda' Baraldi" <pa...@in...> > To: "ALGORITHMS" <alg...@3d...> > Sent: Friday, September 08, 2000 4:24 AM > Subject: [Algorithms] Sorting polys > > > > Hi, i need to sort polygons for alpha blended objects. > > Can you point me to some resource to do that? > > > > thank you > > > > > > _______________________________________________ > > GDAlgorithms-list mailing list > > GDA...@li... > > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list > > _______________________________________________ > GDAlgorithms-list mailing list > GDA...@li... > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list > |
From: Mark W. <mwa...@to...> - 2000-09-08 01:29:38
|
You could try using a hash table indexed on a quantized z-depth. Intersecting polys present a bit of a problem - perhaps a dynamic form of BSP with pooled nodes to avoid dynamic allocation overhead. Mark ----- Original Message ----- From: "Stefano 'Panda' Baraldi" <pa...@in...> To: "ALGORITHMS" <alg...@3d...> Sent: Friday, September 08, 2000 4:24 AM Subject: [Algorithms] Sorting polys > Hi, i need to sort polygons for alpha blended objects. > Can you point me to some resource to do that? > > thank you > > > _______________________________________________ > GDAlgorithms-list mailing list > GDA...@li... > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list |
From: Kevin L. <lac...@in...> - 2000-09-08 01:28:24
|
Yes, E&S is still alive. I'm working for a company just across the street from them. Though the rumor is they are getting out of the 3d hardware business (at least here in Salt Lake). Kevin On Thu, 7 Sep 2000, Akbar A. wrote: > >Evans&Sutherland > what happend to them? > i remember when there name used to be everywhere, > evans that sutherland this... are evans and sutherland still alive? > > wow, i have sure learned a lot from this scene graph topic ;) > i would have *never* guessed that PHIGS would come up in this thread. > > peace, > akbar A. > > > > -----Original Message----- > From: gda...@li... > [mailto:gda...@li...]On Behalf Of > Stephen J Baker > Sent: Thursday, September 07, 2000 4:05 PM > To: gda...@li... > Subject: Re: [Algorithms] FW: [CsMain] Scene Graphs > > > On Thu, 7 Sep 2000, Maciej Sinilo wrote: > > > > http://www.ndl.com/wpapers/bishop.html > > > It provides a good general overview of design philosophies and their > > > implementations for collision detection, culling, traversal, etc. > without > > > delving into their API specifics. > > I find Performer's docs (from SGI's site) very interesting. > > They do delve into API specifics but you can also find some > > very nice general design ideas there. Many SGs seems to be > > more or less inspired by Performer's design. > > Of course Performer was almost certainly inspired by Evans&Sutherland, > Compuscene and Star-Graphicon scene graph *structures* from the > 1980's (which were often implemented in hardware BTW). > > ---- > Science being insufficient - neither ancient protein species deficient. > > Steve Baker (817)619-2657 (Vox/Vox-Mail) > L3Com/Link Simulation & Training (817)619-2466 (Fax) > Work: sj...@li... http://www.link.com > Home: sjb...@ai... http://web2.airmail.net/sjbaker1 > > _______________________________________________ > GDAlgorithms-list mailing list > GDA...@li... > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list > > _______________________________________________ > GDAlgorithms-list mailing list > GDA...@li... > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list > -- |
From: Pierre T. <p.t...@wa...> - 2000-09-07 22:34:31
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It would be interesting, yes... ----- Original Message ----- From: Brown, Greg <Br...@ct...> To: <gda...@li...> Sent: Thursday, September 07, 2000 10:35 PM Subject: RE: [Algorithms] Extracting scale from matrix > > An implementation can be found in the MAX SDK, in Decomp.cpp > > (this is the > > source code for the famous decomp_affine method of the MAX SDK). > > Unfortunately the code is really ugly, and I think it's even > > not included in > > the standard SDK (which only contains headers IIRC). > > There is a bug in this code that will not handle left hand matrices (I > think). There is a new source posted somewhere in the MAX help file. I can > dig it up if anyone needs it. > _______________________________________________ > GDAlgorithms-list mailing list > GDA...@li... > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list |
From: Akbar A. <sye...@ea...> - 2000-09-07 21:43:46
|
>Evans&Sutherland what happend to them? i remember when there name used to be everywhere, evans that sutherland this... are evans and sutherland still alive? wow, i have sure learned a lot from this scene graph topic ;) i would have *never* guessed that PHIGS would come up in this thread. peace, akbar A. -----Original Message----- From: gda...@li... [mailto:gda...@li...]On Behalf Of Stephen J Baker Sent: Thursday, September 07, 2000 4:05 PM To: gda...@li... Subject: Re: [Algorithms] FW: [CsMain] Scene Graphs On Thu, 7 Sep 2000, Maciej Sinilo wrote: > > http://www.ndl.com/wpapers/bishop.html > > It provides a good general overview of design philosophies and their > > implementations for collision detection, culling, traversal, etc. without > > delving into their API specifics. > I find Performer's docs (from SGI's site) very interesting. > They do delve into API specifics but you can also find some > very nice general design ideas there. Many SGs seems to be > more or less inspired by Performer's design. Of course Performer was almost certainly inspired by Evans&Sutherland, Compuscene and Star-Graphicon scene graph *structures* from the 1980's (which were often implemented in hardware BTW). ---- Science being insufficient - neither ancient protein species deficient. Steve Baker (817)619-2657 (Vox/Vox-Mail) L3Com/Link Simulation & Training (817)619-2466 (Fax) Work: sj...@li... http://www.link.com Home: sjb...@ai... http://web2.airmail.net/sjbaker1 _______________________________________________ GDAlgorithms-list mailing list GDA...@li... http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list |
From: Jon A. <jan...@on...> - 2000-09-07 21:38:53
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Thanks. I found it here: http://www.acm.org/tog/GraphicsGems/category.html which incidently lists it as Graphics Gems II, p. 320-323... =) Jon At 11:51 AM 9/7/2000 -0700, you wrote: >Isn't there a DecomposeMatrix routine in one of the Graphics Gems? > >Pass it a 4x4 matrix and it returns rotation, scale, translation, >shear and probably something more... > >...yeah, it's at page 207 of Graphics Gems 4. > >-Blake > > >-----Original Message----- >From: Neal Tringham [mailto:ne...@ps...] >Sent: Thursday, September 07, 2000 10:18 AM >To: gda...@li... >Subject: Re: [Algorithms] Extracting scale from matrix > > > >De: Jon Anderson [mailto:jan...@on...] > > >Are there any good tricks for extracting the scale (x, y, z) from a 4x4 > >matrix? It seems pretty trivial to do it for matrices that consist of > >rotations about a single axis, but I'm having problems doing it for more > >complex matrices. > >If your matrix contains only rotation, scale and translation information, >could you extract the scale factors by comparing the length of the basis >vectors to the length of the normalised basis vectors? > >Note that (even if this works:-)) I don't believe it would allow you to >distinguish between a negative sign in a scale factor (a "mirror") and a >rotation, i.e. it would only allow you to extract the magnitude of the scale >factors, not their signs. > >Curious as to people's comments on this... > >Neal Tringham (Sick Puppies) > >ne...@ps... >ne...@em... > > > > >_______________________________________________ >GDAlgorithms-list mailing list >GDA...@li... >http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list >_______________________________________________ >GDAlgorithms-list mailing list >GDA...@li... >http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list |
From: Stephen J B. <sj...@li...> - 2000-09-07 21:06:02
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On Thu, 7 Sep 2000, Maciej Sinilo wrote: > > http://www.ndl.com/wpapers/bishop.html > > It provides a good general overview of design philosophies and their > > implementations for collision detection, culling, traversal, etc. without > > delving into their API specifics. > I find Performer's docs (from SGI's site) very interesting. > They do delve into API specifics but you can also find some > very nice general design ideas there. Many SGs seems to be > more or less inspired by Performer's design. Of course Performer was almost certainly inspired by Evans&Sutherland, Compuscene and Star-Graphicon scene graph *structures* from the 1980's (which were often implemented in hardware BTW). ---- Science being insufficient - neither ancient protein species deficient. Steve Baker (817)619-2657 (Vox/Vox-Mail) L3Com/Link Simulation & Training (817)619-2466 (Fax) Work: sj...@li... http://www.link.com Home: sjb...@ai... http://web2.airmail.net/sjbaker1 |
From: Brown, G. <Br...@ct...> - 2000-09-07 20:33:17
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> An implementation can be found in the MAX SDK, in Decomp.cpp > (this is the > source code for the famous decomp_affine method of the MAX SDK). > Unfortunately the code is really ugly, and I think it's even > not included in > the standard SDK (which only contains headers IIRC). There is a bug in this code that will not handle left hand matrices (I think). There is a new source posted somewhere in the MAX help file. I can dig it up if anyone needs it. |
From: Jaimi M. <ja...@al...> - 2000-09-07 20:05:08
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Hi Jason -- In my code (not the elliptical code that I still can't get to work right), I handle this by adding invisible clipping solids. These are just polygons that get added to the movement code, but not to the rendering code. This lets me fine tune areas where problems like this arise. Unfortunately, this doesn't work well for terrain, so I've kept my old terrain movement code, which just interpolates heights from the heightmap. I'm interested in what others are doing though, as I'll probably abandon the height-interpolation method when I can get a real clipper in. Jaimi -----Original Message----- From: gda...@li... [mailto:gda...@li...]On Behalf Of Jason Zisk Sent: Thursday, September 07, 2000 11:42 AM To: Algorithms List Subject: [Algorithms] Simple player collision response problem Hi everyone, I've been wrestling with a problem for the past few days and it just won't go away. :) I've been rewriting my player vs. world collision detection and response routines, and I've pretty much got it all finished except for one problem. When the player bumps into or walks along a crease (where two polygon edges meet) the collision response algo seems to make him oscillate. So you'll be walking along in a shallow valley bouncing left and right a tiny bit as you move down the crease. I've taken a look at the quake source and it does something similiar to what I'm doing, except it looks like there is some special case code just for creases. I'd really like to avoid hacking so I'm hoping some of the experts on this list have run into this problem and solved it. Or can outline a simple "slide along polygons" collision response that handles crease situations. What I'm doing now is simply calculating a sliding plane based on the poly the player is hitting and sliding him along that with the remaining velocity after the initial collision. I do this recursively each frame against the environment until the velocity is so small I can just set it to zero. Thanks for any help. - Jason Zisk - nFusion Interactive LLC _______________________________________________ GDAlgorithms-list mailing list GDA...@li... http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list |