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<DIV><FONT size=2>Hi,</FONT></DIV>
<DIV><FONT size=2> Reading back my previus
posts, They may look a bit unfriendly.</FONT></DIV>
<DIV><FONT size=2> If so please consider it just resulting
from of my non-native english nature.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Regards,</FONT></DIV>
<DIV><FONT size=2>Ubit</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=ajlduarte@sapo.pt href="mailto:ajlduarte@sapo.pt">AJLDuarte</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=opensim-dev@lists.berlios.de
href="mailto:opensim-dev@lists.berlios.de">opensim-dev@lists.berlios.de</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, January 05, 2012 12:04
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Opensim-dev] Prospective
ODE physics changes</DIV>
<DIV><BR></DIV>
<DIV><FONT size=2>Hi again,</FONT></DIV>
<DIV><FONT size=2> Forgot to mention that you can find
working code at <A
href="https://github.com/UbitUmarov/Ubit-opensim">https://github.com/UbitUmarov/Ubit-opensim</A> where
i did tried to fix those and other issues</FONT></DIV>
<DIV><FONT size=2> You may see, use, adapt and of
course improve.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Regards,</FONT></DIV>
<DIV><FONT size=2>Ubit</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=ajlduarte@sapo.pt href="mailto:ajlduarte@sapo.pt">AJLDuarte</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=opensim-dev@lists.berlios.de
href="mailto:opensim-dev@lists.berlios.de">opensim-dev@lists.berlios.de</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, January 05, 2012 11:39
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Opensim-dev] Prospective
ODE physics changes</DIV>
<DIV><BR></DIV>
<DIV><FONT size=2>Hi,</FONT></DIV>
<DIV><FONT size=2> Justin, before thicking about reducing
the size of the array passed to ode collide function to receive the colision
contacts information, </FONT><FONT size=2>maybe you should remember what i
told you about managed versus unmanaged memory use in the ode
plugin.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2> Maybe you should think about what is
being done by framework to convert the array from managed memory space to
unmanaged and then back again on each call.</FONT></DIV>
<DIV><FONT size=2> If you do that (or just remember
the details i told you) maybe you will see how to save some cpu
without reducing the stability of the simulation to a useless
state.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2> Also before doing hard testing with
diferent ode supporting libs, maybe you should also review
managed/unmanaged issues on other parts of the plugin. JointCreateContact
? GeomHeightfieldDataBuildSingle ? ....</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2> Best Regards,</FONT></DIV>
<DIV><FONT size=2>Ubit Umarov</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2></FONT> </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=teravus@gmail.com href="mailto:teravus@gmail.com">Teravus
Ovares</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=opensim-dev@lists.berlios.de
href="mailto:opensim-dev@lists.berlios.de">opensim-dev@lists.berlios.de</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, January 04, 2012
7:53 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Opensim-dev]
Prospective ODE physics changes</DIV>
<DIV><BR></DIV>
<DIV>ODE Documentation and examples :)</DIV>
<DIV> </DIV>
<DIV>Regards</DIV>
<DIV><BR>Dan<BR><BR></DIV>
<DIV class=gmail_quote>On Wed, Jan 4, 2012 at 2:46 PM, Justin Clark-Casey
<SPAN dir=ltr><<A
href="mailto:jjustincc@googlemail.com">jjustincc@googlemail.com</A>></SPAN>
wrote:<BR>
<BLOCKQUOTE
style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote>Hi Teravus, nice to hear from you again!<BR><BR>Yes,
more testing is needed, hopefully on OSGrid. But it seems there
may be a tradeoff between having super smooth physics objects and being
able to get more avatars in a scene without encountering cpu limits.
My perception is having more avatars is a more common use case
then lots of physics objects, particularly as OpenSim's current ODE use
does not seem to provide a good physics simulation). Anybody who
does want to try for better physics could always turn the collision
number back up.<BR><BR>In any case, what was the rationale for choosing
80 as the default?
<DIV class=im><BR><BR>On 03/01/12 22:30, Teravus Ovares wrote:<BR></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote>
<DIV class=im>With ODE, it depends on the physics situation.<BR>With
Tri-Mesh and the heightfield collider specifically, ODE generates lots
of small effect contacts and then the<BR>stepper integrates them all
into a contact resolution force. With tri-mesh and the
heightfield, depending on how an<BR>object collides with another,
there could be 20 or 30 contacts that all factor into getting the
object to react<BR>normally. So, to test, you're going to want
to use a stack of 'active'(physical in the client) tri-mesh objects.
You<BR>may also want two or more trimesh LINKSETS to see how
they react.<BR>My guess, is the first thing that you're going to
notice is that a tri-mesh object sitting on another object will
become<BR>more unstable (vibrate more). Each mini-contact
represents a part of the force to keep the object from rotating
from<BR>the other parts of the contact resolution force. As the
effect gets worse, you're going to notice 'rotation anomolies'<BR>that
occur when objects collide.<BR>Think of it like... you
have a cube shaped trimesh... and the cube's corners are
touching a flat ground. In<BR>theory, that would generate 4
contact points for each of the vertices touching the flat ground.
If you cut one off,<BR>then only three of the corners are being
held above ground. On a larger scale, If you do that
enough, then the<BR>object will partially fall through the ground and
then bounce back up from an excessive contact resolution
force<BR>creating instability and vibrating.<BR>Those are the
indicators that I would use to determine if it's OK to make that
change. Are 8 contacts enough for ODE<BR>to react properly in
our usage? That remains to be seen
:).<BR>Regards<BR>Teravus<BR><BR></DIV>
<DIV class=im>On Tue, Jan 3, 2012 at 4:58 PM, Adams, Robert <<A
href="mailto:robert.adams@intel.com"
target=_blank>robert.adams@intel.com</A> <mailto:<A
href="mailto:robert.adams@intel.com"
target=_blank>robert.adams@intel.com</A><U></U>>>
wrote:<BR><BR> > ...<BR> > According
to [2], the maximum reported scripting collision contacts is
8.<BR> ><BR> > Testing with 8 on
Wright Plaza today in the Tuesday meeting seemed to greatly reduce
physics scene time compared to<BR> > previously
without any apparent loss of required fidelity (50ms with 18 avatars,
albeit mostly sitting down -<BR> > unfortunately I
didn't record previous week's numbers but they were higher.
Nebadon tested one of his vehicles).<BR><BR> Looking
at the code, contacts_per_collision is the number of collision points
reported by ODE for each collision --<BR> like a prim
sitting on rough terrain and touching multiple places on the ground.
Reducing the count to 8 means that<BR> no more than 8
contact points will be reported by ODE and, if there are more, you
can't be sure you get the 'best' ones.<BR><BR> I suspect
that most of the time there are only a few contact points so it
doesn't make sense that reducing the<BR> number from 80 to
8 would significantly reduce the compute time. If it is the number of
contact points causing the<BR> computation overhead then
ODE must be normally returning more than 8 contact points. Is this
really the case? Or is<BR> something else going
on?<BR><BR> -- ra<BR>
______________________________<U></U>_________________<BR>
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target=_blank>Opensim-dev@lists.berlios.de</A> <mailto:<A
href="mailto:Opensim-dev@lists.berlios.de"
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<A href="https://lists.berlios.de/mailman/listinfo/opensim-dev"
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<DIV
class=im><BR><BR><BR><BR><BR>______________________________<U></U>_________________<BR>Opensim-dev
mailing list<BR><A href="mailto:Opensim-dev@lists.berlios.de"
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target=_blank>https://lists.berlios.de/<U></U>mailman/listinfo/opensim-dev</A><BR></DIV></BLOCKQUOTE><BR>
<DIV class=im><BR>-- <BR>Justin Clark-Casey (justincc)<BR><A
href="http://justincc.org/blog"
target=_blank>http://justincc.org/blog</A><BR><A
href="http://twitter.com/justincc"
target=_blank>http://twitter.com/justincc</A><BR></DIV>
<DIV>
<DIV></DIV>
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