Re: [vos-d] thought problem 1: physics
On 2/3/07, Reed Hedges <[EMAIL PROTECTED]> wrote: > Benjamin Mesing wrote: > >> Question: will the two images of the two experiments show box2 in the > >> same rest position relative to box1? > > > > Why don't we consider floating point precision issues as computers > > equivalent to Heisenbergs uncertainty principle? > > Well, OK not to be pedantic or anything :) but the problem is not > uncertain, we know very certainly that it's going to happen, whether we > observe it or not. It's not that bad an analogy: the location of things *is* uncertain in that, for any one coordinate, it will "jump" to one of eight positions that are the nearest representable locations at a given precision and distance from origin. When measuring or comparing between two locations they could diverge in opposite directions or converge doubling the normal error that you'd expect form the "cube". And in certain rare cases the error is larger. Then the effects of calculation error propagation make it worse, etc. chris > > ___ > vos-d mailing list > vos-d@interreality.org > http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d > ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
Benjamin Mesing wrote: >> Question: will the two images of the two experiments show box2 in the >> same rest position relative to box1? > > Why don't we consider floating point precision issues as computers > equivalent to Heisenbergs uncertainty principle? Well, OK not to be pedantic or anything :) but the problem is not uncertain, we know very certainly that it's going to happen, whether we observe it or not. ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
chris wrote: > Consider the case when a military simulation > is used to generate images that they expect a sensor should "see". > These images are compared to "ground truth" images and the result is > used to calibrate a sensor - which is then used in a craft or weapon. > If there is unknown positional error affecting the simulated image > (and most practitioners are unaware of the effect of > spatial/positional error on rendered images) then the sensor gets > miss-calibrated. If the calibration procedure includes the range where errors like that then it should model the error. (After all, that's the point of calibration.) ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
On 2/2/07, Benjamin Mesing <[EMAIL PROTECTED]> wrote: > > > Question: will the two images of the two experiments show box2 in the > > same rest position relative to box1? > > Why don't we consider floating point precision issues as computers > equivalent to Heisenbergs uncertainty principle? :) It does seem like that sometimes, chris > > Sorry, could help it ;-) > > Regards Ben > > > ___ > vos-d mailing list > vos-d@interreality.org > http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d > ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
On Fri, Feb 02, 2007 at 04:42:06PM +0900, chris wrote: > poor AI! Nice example, reminds me of the Ai used to > translate English/Russian. It was asked to translate "The spirit is > willing but the flesh is weak" and came back with : > "The wine is good but the meat is rotten"! When the first speech recognizer was finished, the scientists wondered what should be the first words to be recognized. Being the boring scientists they are, they settled for "Recognize speech.". Little did they know that they'd "Wreck a nice beach.". Liebe Grüße, Sebastian Hoffmann -- "Glücklich zu sein ist oberste Bürgerpflicht." -- Paranoia, West End Games "Oh, look at the time, 1984 already." -- Daria (MTV) ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
> Sorry, could help it ;-) Obviously this should read couldn't... ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
> Question: will the two images of the two experiments show box2 in the > same rest position relative to box1? Why don't we consider floating point precision issues as computers equivalent to Heisenbergs uncertainty principle? Sorry, could help it ;-) Regards Ben ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
On 2/2/07, Sebastian Hoffmann <[EMAIL PROTECTED]> wrote: On Fri, Feb 02, 2007 at 04:06:08PM +0900, chris wrote: > for time, with the python-ode example, i did not see much diversion > until about 8000. Thank you, at which stepsize? atached are two of the programs - the second having time=8000. I used a VIAO noebook, pentium 770, running windoze. The software I used was according to these instructions by Miriam English: Here are the 7 steps to success (at least on a Win98 machine): 1. installed python 2.4 python-2.4.3.msi http://www.python.org/ftp/python/2.4.3/ 2. edited autoexec.bat to add: SET PATH=%PATH%;C:\python SET PYTHON=C:\PYTHON\ 3. installed pyOpenGL PyOpenGL-2.0.2.01.py2.4-numpy23.exe http://pyopengl.sourceforge.net 4. Copied glut32.dll to the C:\python\Lib\site-packages\OpenGL directory. (This is a *crucial* step.) glut32.dll http://www.xmission.com/%7Enate/glut.html 5. installed OpenGLContext OpenGLContext-2.0.0c1.win32-py2.4.exe http://pyopengl.sourceforge.net/context/ (downloaded from http://pyopengl.sourceforge.net/ ) 6. installed PIL (python Image Library) PIL-1.1.5.win32-py2.4.exe http://www.pythonware.com/products/pil/ 7. installed pyODE PyODE-1.1.0.win32-py2.4.exe http://pyode.sourceforge.net/ Now I can double-click on the tutorial3.py from http://pyode.sourceforge.net/ and it simply runs! > to me, the scary thing is that people tend to assume When people start to assume, bad things always start to happen. :) > that a computer > simulation, programmed with high precision and all, is going to be > accurate and reliable. Consider the case when a military simulation > is used to generate images that they expect a sensor should "see". > These images are compared to "ground truth" images and the result is > used to calibrate a sensor - which is then used in a craft or weapon. > If there is unknown positional error affecting the simulated image > (and most practitioners are unaware of the effect of > spatial/positional error on rendered images) then the sensor gets > miss-calibrated. There's an anecdote in university cycles about an AI trained to find camouflaged tanks. It used a neural net which could classify pictures shown to it into "tank present" or "no tank present" and was trained by being fed images and the information wether a tank was present. In the lab it worked great. In the wild, it was completely useless, Never worked. In the postmortem analysis, someone found that all the pictures of tankless wild had been done when light was best (day), but the tanks pictures where taken when camouflage was best (dawn and dusk). Meditate on what what the AIs mind was like. :) poor AI! Nice example, reminds me of the Ai used to translate English/Russian. It was asked to translate "The spirit is willing but the flesh is weak" and came back with : "The wine is good but the meat is rotten"! chris Liebe Grüße, Sebastian Hoffmann -- "Glücklich zu sein ist oberste Bürgerpflicht." -- Paranoia, West End Games "Oh, look at the time, 1984 already." -- Daria (MTV) ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d # pyODE example 3: Collision detection # origin # Originally by Matthias Baas. # Updated by Pierre Gay to work without pygame or cgkit. import sys, os, random, time from math import * from OpenGL.GL import * from OpenGL.GLU import * from OpenGL.GLUT import * import ode # geometric utility functions def scalp (vec, scal): vec[0] *= scal vec[1] *= scal vec[2] *= scal def length (vec): return sqrt (vec[0]**2 + vec[1]**2 + vec[2]**2) # prepare_GL def prepare_GL(): """Prepare drawing. """ # Viewport glViewport(0,0,640,480) # Initialize glClearColor(0.8,0.8,0.9,0) glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_DEPTH_TEST) glDisable(GL_LIGHTING) glEnable(GL_LIGHTING) glEnable(GL_NORMALIZE) glShadeModel(GL_FLAT) # Projection glMatrixMode(GL_PROJECTION) glLoadIdentity() gluPerspective (45,1.,0.2,20) # Initialize ModelView matrix glMatrixMode(GL_MODELVIEW) glLoadIdentity() # Light source glLightfv(GL_LIGHT0,GL_POSITION,[0,0,1,0]) glLightfv(GL_LIGHT0,GL_DIFFUSE,[1,1,1,1]) glLightfv(GL_LIGHT0,GL_SPECULAR,[1,1,1,1]) glEnable(GL_LIGHT0) # View transformation gluLookAt (2.4, 3.6, 4.8, 0.5, 0.5, 0, 0, 1, 0) # draw_body def draw_body(body): """Draw an ODE body. """ x,y,z = body.getPosition() R = body.getRotation() #rot = [R[0], R[3], R[6], 0., # R[1], R[4], R[7], 0., # R[2], R[5], R[8], 0., # x, y, z, 1.0] rot = [1, 0.0, 0.0, 0.0, 0.0, 1, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, x, y, z, 1.0] glPushMatrix() glMultMatrixd(rot) if body.shape=="box": sx
Re: [vos-d] thought problem 1: physics
On Fri, Feb 02, 2007 at 04:06:08PM +0900, chris wrote: > for time, with the python-ode example, i did not see much diversion > until about 8000. Thank you, at which stepsize? > to me, the scary thing is that people tend to assume When people start to assume, bad things always start to happen. :) > that a computer > simulation, programmed with high precision and all, is going to be > accurate and reliable. Consider the case when a military simulation > is used to generate images that they expect a sensor should "see". > These images are compared to "ground truth" images and the result is > used to calibrate a sensor - which is then used in a craft or weapon. > If there is unknown positional error affecting the simulated image > (and most practitioners are unaware of the effect of > spatial/positional error on rendered images) then the sensor gets > miss-calibrated. There's an anecdote in university cycles about an AI trained to find camouflaged tanks. It used a neural net which could classify pictures shown to it into "tank present" or "no tank present" and was trained by being fed images and the information wether a tank was present. In the lab it worked great. In the wild, it was completely useless, Never worked. In the postmortem analysis, someone found that all the pictures of tankless wild had been done when light was best (day), but the tanks pictures where taken when camouflage was best (dawn and dusk). Meditate on what what the AIs mind was like. :) Liebe Grüße, Sebastian Hoffmann -- "Glücklich zu sein ist oberste Bürgerpflicht." -- Paranoia, West End Games "Oh, look at the time, 1984 already." -- Daria (MTV) ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
On 2/2/07, Sebastian Hoffmann <[EMAIL PROTECTED]> wrote: > On Thu, Feb 01, 2007 at 10:15:19PM -0800, Ken Taylor wrote: > > > yeah - but my tests of the position sensitivity are quite scary for > > > anything u want > > > to be accurate or repeatable and for mission critical stuff. > > > > But would this kind of experiment be reproducable in the real world, even > > with super-precision equipment? > > How scary *is* it actually? After which time does the simulation start to > diverge visibly? And, if you happen to be in a mood for tinkering, what for time, with the python-ode example, i did not see much diversion until about 8000. for a spatial displacement 10m was enough. f > happens if you update the second simulation with data from the first > simulation every $time? to me, the scary thing is that people tend to assume that a computer simulation, programmed with high precision and all, is going to be accurate and reliable. Consider the case when a military simulation is used to generate images that they expect a sensor should "see". These images are compared to "ground truth" images and the result is used to calibrate a sensor - which is then used in a craft or weapon. If there is unknown positional error affecting the simulated image (and most practitioners are unaware of the effect of spatial/positional error on rendered images) then the sensor gets miss-calibrated. chris > > Liebe Grüße, > Sebastian Hoffmann > -- > "Glücklich zu sein ist oberste Bürgerpflicht." > -- Paranoia, West End Games > "Oh, look at the time, 1984 already." > -- Daria (MTV) > > ___ > vos-d mailing list > vos-d@interreality.org > http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d > ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
On Thu, Feb 01, 2007 at 10:15:19PM -0800, Ken Taylor wrote: > > yeah - but my tests of the position sensitivity are quite scary for > > anything u want > > to be accurate or repeatable and for mission critical stuff. > > But would this kind of experiment be reproducable in the real world, even > with super-precision equipment? How scary *is* it actually? After which time does the simulation start to diverge visibly? And, if you happen to be in a mood for tinkering, what happens if you update the second simulation with data from the first simulation every $time? Liebe Grüße, Sebastian Hoffmann -- "Glücklich zu sein ist oberste Bürgerpflicht." -- Paranoia, West End Games "Oh, look at the time, 1984 already." -- Daria (MTV) ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
On 2/2/07, Ken Taylor <[EMAIL PROTECTED]> wrote: > > chris wrote: > > On 2/2/07, Peter Amstutz <[EMAIL PROTECTED]> wrote: > > > Well, I assume this is a trick question. Obviously it *should* do the > > > same thing, but because of tiny changes in floating point precision, > > > that isn't guaranteed, and the further you go the less likely it is to > > > produce the same results. Do I get a cookie? > > > > yup - even tho it is only 10m the difference can be surprisingly large > > and obvious just from looking at image: out of proportion to the > > difference in resolution at 10m (which is about 1.6 x 10^-15). See > > attached image. > > Dr Ian Malcom? Is that you? ;) Whah, who? > > > yeah - but my tests of the position sensitivity are quite scary for > > anything u want > > to be accurate or repeatable and for mission critical stuff. > > But would this kind of experiment be reproducable in the real world, even > with super-precision equipment? I wouldn't expect to be able to drop a block > and have it do the same thing every time. I guess a more pertinent question > is -- are there things which *are* repeatable in the real world but would > fail due to this kind of position sensitivity in simulation? I think a RL equivalent, in theory, is likely to be *more precisely* repeatable because real world has infinite resolution and a very finely controlled physics experiment is likely to produce closer results. The important issue here is that you have more precise control over the computer sim but less precise results output for these highly sensitive sims. But if you also control the location of the experiment and point of observation then you can get more predictable, accurate results (even identical) on the computer. chris > > -Ken > > > ___ > vos-d mailing list > vos-d@interreality.org > http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d > ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
chris wrote: > On 2/2/07, Peter Amstutz <[EMAIL PROTECTED]> wrote: > > Well, I assume this is a trick question. Obviously it *should* do the > > same thing, but because of tiny changes in floating point precision, > > that isn't guaranteed, and the further you go the less likely it is to > > produce the same results. Do I get a cookie? > > yup - even tho it is only 10m the difference can be surprisingly large > and obvious just from looking at image: out of proportion to the > difference in resolution at 10m (which is about 1.6 x 10^-15). See > attached image. Dr Ian Malcom? Is that you? ;) > yeah - but my tests of the position sensitivity are quite scary for > anything u want > to be accurate or repeatable and for mission critical stuff. But would this kind of experiment be reproducable in the real world, even with super-precision equipment? I wouldn't expect to be able to drop a block and have it do the same thing every time. I guess a more pertinent question is -- are there things which *are* repeatable in the real world but would fail due to this kind of position sensitivity in simulation? -Ken ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
On 2/2/07, Peter Amstutz <[EMAIL PROTECTED]> wrote: > That's very interesting. Which simulation engine is this? ode - used in python-ode code. I can provide code and install instructions if u like. > > Also, to reiterate my previous email, would fixed-point math improve the > situation any? > see reply to last post. > I suppose one thing to keep in mind is rigid body simulation for the > purposes of games just needs to be "good enough" and look reasonable. > Practical uses of rigid body physics in games that I have seen tend to > have quite a lot of dampening to prevent the system from flipping out. > yeah - but my tests of the position sensitivity are quite scary for anything u want to be accurate or repeatable and for mission critical stuff. > Physics is something I haven't solved in VOS. The current ter'angreal > uses client-side "physics" (really just trivial graviy and collision > detection) but proper rigid body physics (so that users can push and > pull things, stack things up and knock them over, etc) will likely need > to be managed by the server. > > On Fri, Feb 02, 2007 at 11:29:35AM +0900, chris wrote: > > On 2/2/07, Peter Amstutz <[EMAIL PROTECTED]> wrote: > > >Well, I assume this is a trick question. Obviously it *should* do the > > >same thing, but because of tiny changes in floating point precision, > > >that isn't guaranteed, and the further you go the less likely it is to > > >produce the same results. Do I get a cookie? > > > > yup - even tho it is only 10m the difference can be surprisingly large > > and obvious just from looking at image: out of proportion to the > > difference in resolution at 10m (which is about 1.6 x 10^-15). See > > attached image. > > > > chris > > > > > > > ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
That's very interesting. Which simulation engine is this? Also, to reiterate my previous email, would fixed-point math improve the situation any? I suppose one thing to keep in mind is rigid body simulation for the purposes of games just needs to be "good enough" and look reasonable. Practical uses of rigid body physics in games that I have seen tend to have quite a lot of dampening to prevent the system from flipping out. Physics is something I haven't solved in VOS. The current ter'angreal uses client-side "physics" (really just trivial graviy and collision detection) but proper rigid body physics (so that users can push and pull things, stack things up and knock them over, etc) will likely need to be managed by the server. On Fri, Feb 02, 2007 at 11:29:35AM +0900, chris wrote: > On 2/2/07, Peter Amstutz <[EMAIL PROTECTED]> wrote: > >Well, I assume this is a trick question. Obviously it *should* do the > >same thing, but because of tiny changes in floating point precision, > >that isn't guaranteed, and the further you go the less likely it is to > >produce the same results. Do I get a cookie? > > yup - even tho it is only 10m the difference can be surprisingly large > and obvious just from looking at image: out of proportion to the > difference in resolution at 10m (which is about 1.6 x 10^-15). See > attached image. > > chris > > > >On Fri, Feb 02, 2007 at 09:26:43AM +0900, chris wrote: > >> This is in response to Reed's question in earlier thread. > >> > >> Thought problem 1: physics > >> > >> Suppose I am going to do a rigid body simulation. I put one box (box1) > >> on a plane, at the origin and hold another box (box2) suspended a > >> meter above the plane nearby. I release box2 at time t=20 and it > >> bounces, perhaps collides with box1 then eventually comes to rest. I > >> snap an image of the rest state of the sim. > >> > >> Now I repeat the entire sim after first shifting everything (boxes and > >> plane) by 10m. The boxes and plane are in exactly the same relative > >> position as before. I drop box2 at t=20, let it bounce and snap an > >> image of the sim when it is at rest. > >> > >> Question: will the two images of the two experiments show box2 in the > >> same rest position relative to box1? > >> > >> ___ > >> vos-d mailing list > >> vos-d@interreality.org > >> http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d > > > >-- > >[ Peter Amstutz ][ [EMAIL PROTECTED] ][ [EMAIL PROTECTED] ] > >[Lead Programmer][Interreality Project][Virtual Reality for the Internet] > >[ VOS: Next Generation Internet Communication][ http://interreality.org ] > >[ http://interreality.org/~tetron ][ pgpkey: pgpkeys.mit.edu 18C21DF7 ] > > > > > >-BEGIN PGP SIGNATURE- > >Version: GnuPG v1.4.5 (GNU/Linux) > > > >iD8DBQFFwptgaeHUyhjCHfcRAsn5AJ9knheBn1d+AOS7dbG55DH04+JomQCeP4ci > >TrZzW9jOvE3o+MY3TEyCrjA= > >=xS/U > >-END PGP SIGNATURE- > > > >___ > >vos-d mailing list > >vos-d@interreality.org > >http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d > > > > > ___ > vos-d mailing list > vos-d@interreality.org > http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d -- [ Peter Amstutz ][ [EMAIL PROTECTED] ][ [EMAIL PROTECTED] ] [Lead Programmer][Interreality Project][Virtual Reality for the Internet] [ VOS: Next Generation Internet Communication][ http://interreality.org ] [ http://interreality.org/~tetron ][ pgpkey: pgpkeys.mit.edu 18C21DF7 ] signature.asc Description: Digital signature ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
On 2/2/07, Peter Amstutz <[EMAIL PROTECTED]> wrote: Well, I assume this is a trick question. Obviously it *should* do the same thing, but because of tiny changes in floating point precision, that isn't guaranteed, and the further you go the less likely it is to produce the same results. Do I get a cookie? yup - even tho it is only 10m the difference can be surprisingly large and obvious just from looking at image: out of proportion to the difference in resolution at 10m (which is about 1.6 x 10^-15). See attached image. chris On Fri, Feb 02, 2007 at 09:26:43AM +0900, chris wrote: > This is in response to Reed's question in earlier thread. > > Thought problem 1: physics > > Suppose I am going to do a rigid body simulation. I put one box (box1) > on a plane, at the origin and hold another box (box2) suspended a > meter above the plane nearby. I release box2 at time t=20 and it > bounces, perhaps collides with box1 then eventually comes to rest. I > snap an image of the rest state of the sim. > > Now I repeat the entire sim after first shifting everything (boxes and > plane) by 10m. The boxes and plane are in exactly the same relative > position as before. I drop box2 at t=20, let it bounce and snap an > image of the sim when it is at rest. > > Question: will the two images of the two experiments show box2 in the > same rest position relative to box1? > > ___ > vos-d mailing list > vos-d@interreality.org > http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d -- [ Peter Amstutz ][ [EMAIL PROTECTED] ][ [EMAIL PROTECTED] ] [Lead Programmer][Interreality Project][Virtual Reality for the Internet] [ VOS: Next Generation Internet Communication][ http://interreality.org ] [ http://interreality.org/~tetron ][ pgpkey: pgpkeys.mit.edu 18C21DF7 ] -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.5 (GNU/Linux) iD8DBQFFwptgaeHUyhjCHfcRAsn5AJ9knheBn1d+AOS7dbG55DH04+JomQCeP4ci TrZzW9jOvE3o+MY3TEyCrjA= =xS/U -END PGP SIGNATURE- ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d dropBlock0cf10.png Description: PNG image ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
Re: [vos-d] thought problem 1: physics
Well, I assume this is a trick question. Obviously it *should* do the same thing, but because of tiny changes in floating point precision, that isn't guaranteed, and the further you go the less likely it is to produce the same results. Do I get a cookie? On Fri, Feb 02, 2007 at 09:26:43AM +0900, chris wrote: > This is in response to Reed's question in earlier thread. > > Thought problem 1: physics > > Suppose I am going to do a rigid body simulation. I put one box (box1) > on a plane, at the origin and hold another box (box2) suspended a > meter above the plane nearby. I release box2 at time t=20 and it > bounces, perhaps collides with box1 then eventually comes to rest. I > snap an image of the rest state of the sim. > > Now I repeat the entire sim after first shifting everything (boxes and > plane) by 10m. The boxes and plane are in exactly the same relative > position as before. I drop box2 at t=20, let it bounce and snap an > image of the sim when it is at rest. > > Question: will the two images of the two experiments show box2 in the > same rest position relative to box1? > > ___ > vos-d mailing list > vos-d@interreality.org > http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d -- [ Peter Amstutz ][ [EMAIL PROTECTED] ][ [EMAIL PROTECTED] ] [Lead Programmer][Interreality Project][Virtual Reality for the Internet] [ VOS: Next Generation Internet Communication][ http://interreality.org ] [ http://interreality.org/~tetron ][ pgpkey: pgpkeys.mit.edu 18C21DF7 ] signature.asc Description: Digital signature ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
[vos-d] thought problem 1: physics
This is in response to Reed's question in earlier thread. Thought problem 1: physics Suppose I am going to do a rigid body simulation. I put one box (box1) on a plane, at the origin and hold another box (box2) suspended a meter above the plane nearby. I release box2 at time t=20 and it bounces, perhaps collides with box1 then eventually comes to rest. I snap an image of the rest state of the sim. Now I repeat the entire sim after first shifting everything (boxes and plane) by 10m. The boxes and plane are in exactly the same relative position as before. I drop box2 at t=20, let it bounce and snap an image of the sim when it is at rest. Question: will the two images of the two experiments show box2 in the same rest position relative to box1? ___ vos-d mailing list vos-d@interreality.org http://www.interreality.org/cgi-bin/mailman/listinfo/vos-d
