===Havok4 Public Beta 1 Release Notes===

This release of the Second Life simulator includes an upgrade of the Havok physics engine to v4. This is an internal update release, not a "new features" release from a physics perspective.

===Public Beta Test Grid===
We expect the public beta test for Havok4 to be very active, with many participants. We have prepared a test grid that allows for many types of physics-related tests. The test regions will include:
* Orientation Islands
* Welcome Areas
* Lusk
* Several sandboxes
* Combat sandboxes
* Vehicle testing simulators

NOTE: The Public Beta viewer will be configured to use the beta grid, which will be a snapshot copy of portions of the main grid and a copy of your user account. You can do "anything you want" on this grid without risking damage to your "real account" on the main grid.

===How Do I Stay "In The Loop" With Havok4 Testing?===
# Attend "[[Regular_Havok4_Office_Hours_In-World|Regular Havok4 Office Hours In-World]]"
# TELL US about everything you find using the Public Issue Tracker at "[https://jira.secondlife.com/ Issue Tracker]" 
Please enter bugs using PROJECT "Second Life Service - SVC" and COMPONENT "Physics"!

===Known Issues===
The following issues are known in the current Second Life Havok4 build, and several of them are already being worked on. We decided not to hold off on releasing the public beta for these, and will update the server code on the public beta test simulators as we have fixes completed.

* Kart stops too quickly (and tumbles too easily when going over bumps, as well as some odd collision behavior)

* Bonifacio has very high script time (and is running VERY slowly)

* Short-range teleport script not working correctly

* Flocking birds script behaves differently on Havok4 (birds acquire extra energy over time and eventually "rocket" out of sim)

* Some physical TargetOmega objects do not spin

* Sitting on anything but top face of a box will fail

* C-Tech 2050 hover ship spirals out of control after several minutes of flying and turning

* Sitting avatars do not always contact seat

* Making an object non-physical while it's rolling leaves it rotating

* Bouncing off of a plane is different if the plane is physical or non physical

* Drop a large cube on a small cube, they interpenetrate when they shouldn't

* A sphere interpenetrating into a larger object can launch both

* Physical spheres on uneven ground sink into the ground

* Your avatar direction does not update on other viewers (Avatar A turns, avatar b's viewer does not update showing the rotation until Avatar A does something else such as walk, run, jump or fly)

* In some cases maximum link distance exceeds 32m

* Vehicles collide with phantom tubes, rings, and torii

* Some complex vehicles show incorrect behavior

Havok4

2007-09-28T21:44:57Z

Sidewinder Linden:

Havok4/Beta1 Release Notes

2007-09-28T21:44:45Z

Sidewinder Linden:

===Havok4 Public Beta 1 Release Notes===

This release of the Second Life simulator includes an upgrade of the Havok physics engine to v4. This is an internal update release, not a "new features" release from a physics perspective.

===Public Beta Test Grid===
We expect the public beta test for Havok4 to be very active, with many participants. We have prepared a test grid that allows for many types of physics-related tests. The test regions will include:
* Orientation Islands
* Welcome Areas
* Lusk
* Several sandboxes
* Combat sandboxes
* Vehicle testing simulators

NOTE: The Public Beta viewer will be configured to use the beta grid, which will be a snapshot copy of portions of the main grid and a copy of your user account. You can do "anything you want" on this grid without risking damage to your "real account" on the main grid.

===How Do I Stay "In The Loop" With Havok4 Testing?===
# Attend "[[Regular_Havok4_Office_Hours_In-World|Regular Havok4 Office Hours In-World]]"
# TELL US about everything you find using the [[Issue_tracker|Public Issue Tracker]] 
Please enter bugs using PROJECT "Second Life Service - SVC" and COMPONENT "Physics"!

===Known Issues===
The following issues are known in the current Second Life Havok4 build, and several of them are already being worked on. We decided not to hold off on releasing the public beta for these, and will update the server code on the public beta test simulators as we have fixes completed.

* Kart stops too quickly (and tumbles too easily when going over bumps, as well as some odd collision behavior)

* Bonifacio has very high script time (and is running VERY slowly)

* Short-range teleport script not working correctly

* Flocking birds script behaves differently on Havok4 (birds acquire extra energy over time and eventually "rocket" out of sim)

* Some physical TargetOmega objects do not spin

* Sitting on anything but top face of a box will fail

* C-Tech 2050 hover ship spirals out of control after several minutes of flying and turning

* Sitting avatars do not always contact seat

* Making an object non-physical while it's rolling leaves it rotating

* Bouncing off of a plane is different if the plane is physical or non physical

* Drop a large cube on a small cube, they interpenetrate when they shouldn't

* A sphere interpenetrating into a larger object can launch both

* Physical spheres on uneven ground sink into the ground

* Your avatar direction does not update on other viewers (Avatar A turns, avatar b's viewer does not update showing the rotation until Avatar A does something else such as walk, run, jump or fly)

* In some cases maximum link distance exceeds 32m

* Vehicles collide with phantom tubes, rings, and torii

* Some complex vehicles show incorrect behavior

Havok4/Office Hours

2007-09-28T21:44:03Z

Sidewinder Linden:

Office Hours will be held at the Brampton Linden Stage 
Brampton 106/166/25 

[http://slurl.com/secondlife/Brampton/106/166/25/?title=Havok4%20Public%20Beta%201%20Office%20Hours Brampton Linden Stage SLURL]

THIS Saturday September 29, 2007 08:00 PDT

Tuesdays 21:00 PDT (ongoing)

Thursdays 08:00 PDT (starting October 4, 2007

Havok4/Office Hours

2007-09-28T21:43:47Z

Sidewinder Linden: New page: Office Hours will be held at the Brampton Linden Stage (Brampton 106/166/25 [http://slurl.com/secondlife/Brampton/106/166/25/?title=Havok4%20Public%20Beta%201%20Office%20Hours Brampton Lin...

Office Hours will be held at the Brampton Linden Stage (Brampton 106/166/25
[http://slurl.com/secondlife/Brampton/106/166/25/?title=Havok4%20Public%20Beta%201%20Office%20Hours Brampton Linden Stage SLURL]

THIS Saturday September 29, 2007 08:00 PDT

Tuesdays 21:00 PDT (ongoing)

Thursdays 08:00 PDT (starting October 4, 2007

Havok4/Beta1 Release Notes

2007-09-28T21:39:56Z

Sidewinder Linden: New page: ===Havok4 Public Beta 1 Release Notes=== This release of the Second Life simulator includes an upgrade of the Havok physics engine to v4. This is an internal update release, not a "new fe...

===Havok4 Public Beta 1 Release Notes===

This release of the Second Life simulator includes an upgrade of the Havok physics engine to v4. This is an internal update release, not a "new features" release from a physics perspective.

===Public Beta Test Grid===
We expect the public beta test for Havok4 to be very active, with many participants. We have prepared a test grid that allows for many types of physics-related tests. The test regions will include:
* Orientation Islands
* Welcome Areas
* Lusk
* Several sandboxes
* Combat sandboxes
* Vehicle testing simulators

NOTE: The Public Beta viewer will be configured to use the beta grid, which will be a snapshot copy of portions of the main grid and a copy of your user account. You can do "anything you want" on this grid without risking damage to your "real account" on the main grid.

===How Do I Stay "In The Loop" With Havok4 Testing?===
# Attend "[[Havok4_Office_Hours|Regular Havok4 Office Hours In-World]]"
# TELL US about everything you find using the [[Issue_tracker|Public Issue Tracker]] 
Please enter bugs using PROJECT "Second Life Service - SVC" and COMPONENT "Physics"!

===Known Issues===
The following issues are known in the current Second Life Havok4 build, and several of them are already being worked on. We decided not to hold off on releasing the public beta for these, and will update the server code on the public beta test simulators as we have fixes completed.

* Kart stops too quickly (and tumbles too easily when going over bumps, as well as some odd collision behavior)

* Bonifacio has very high script time (and is running VERY slowly)

* Short-range teleport script not working correctly

* Flocking birds script behaves differently on Havok4 (birds acquire extra energy over time and eventually "rocket" out of sim)

* Some physical TargetOmega objects do not spin

* Sitting on anything but top face of a box will fail

* C-Tech 2050 hover ship spirals out of control after several minutes of flying and turning

* Sitting avatars do not always contact seat

* Making an object non-physical while it's rolling leaves it rotating

* Bouncing off of a plane is different if the plane is physical or non physical

* Drop a large cube on a small cube, they interpenetrate when they shouldn't

* A sphere interpenetrating into a larger object can launch both

* Physical spheres on uneven ground sink into the ground

* Your avatar direction does not update on other viewers (Avatar A turns, avatar b's viewer does not update showing the rotation until Avatar A does something else such as walk, run, jump or fly)

* In some cases maximum link distance exceeds 32m

* Vehicles collide with phantom tubes, rings, and torii

* Some complex vehicles show incorrect behavior

Havok4

2007-09-28T21:38:53Z

Sidewinder Linden: /* Introduction */

Havok4

2007-09-28T21:38:25Z

Sidewinder Linden: /* Havok4 (New Physics Engine) Beta Test Information Hub */

Havok4

2007-09-28T21:34:15Z

Sidewinder Linden:

Havok4 Beta Test Ideas

2007-09-28T21:08:31Z

2007-09-28T20:52:48Z

Sidewinder Linden: New page: === Linkability formulae === Consider two primitives, A and B. The maximum distance at which they can be linked is given by the following formula: (1) max_link_distance = minimu...

=== Linkability formulae ===

Consider two primitives, A and B. The maximum distance at which they can be
linked is given by the following formula:

(1) max_link_distance = minimum( diameter_A + diameter_B + SMALLEST_MAX, LARGEST_MAX )

where:

(3) SMALLEST_MAX = 1.0 meters
(4) LARGEST_MAX = 32.0 meters
(5) diameter_X = diameter of the primitive X's ''bounding sphere'' (Figure A)
(6) minimum(C, D) = C if less than D, otherwise D

If the distance between ''the geometric centers'' of the two primitives is less
than or equal to max_link_distance then they can be linked. Put in mathematical
terms:

(7) A_can_link_to_B = ( length(center_A - center_B) <= max_link_distance )

{|align="right"
|[[Image:Primitive_diameter.png]]
|}
The '''bounding sphere''' is the smallest sphere that totally encloses the
primitive's ''local bounding box''.

The '''local bounding box''' is centered at the primitive's ''geometric center'' and
whose local-frame sides are equal to the primitive's ''scale''.

The '''geometric center''' of the primitive is its local symmetric center prior to
any ''cut'', ''shear'', ''twist'', ''taper'', or ''hollow'' operations.

'''Note''' that a primitive's bounding sphere is not necessarily the tightest sphere
possible for its shape, unless it is a simple box or sphere. The bounding sphere
depends only on the primitive's position and scale, so any
severly cut and hollowed primitive will be significantly smaller than its bounding
sphere, and not necessarily near the center. Also, a primitive with twist and/or
shear may have corners that extend outside of its bounding sphere. Since the
linkability rules depend only on the bounding sphere, which is ultimately dependent
only on the primitive's position and scale, the linkability of two prims is independent
of changes to form and rotation.
 
{|align="right"
|[[Image:Link_rules.png]]
|}
 
=== Linkability algorithm ===
{|align="right"
|[[Image:Fig_c.png]]
|}

The rules governing the '''linkability of multi-prim objects''' is very similar to
the two-primitive case. The same formulae (1) and (7) apply, but the
bounding spheres of multi-prim objects are the smallest spheres that completely
contain all of the bounding spheres of the corresponding primitives. (See Figure C)

When linking '''three or more objects''' the algorithm iterates over the candidate
objects until all linkable pieces have been found. First the root object
is tested against each candidate object and the larger bounding sphere is
recomputed after a successful link. Then any unlinked pieces are tested between
themselves and merged into larger collections according to the formulae. The
root object is then re-tested against the modified candidates and the process
continues until all objects are linked, or no new links have been found.

=== Failure modes ===

If an '''unlinkable set''' is tested by the linkability algorithm then the final subset
of linkable parts is determined by the order in which the candidates were submitted.
The trivial proof for this is to consider a root primitive in the middle of an infinite
grid of other primitives. It can't link to everything, but it were first tested against
all primitives west of it the final linkable subset of that first operation might not
link to any primitives to the east because of the LARGEST_MAX requirement (4). If the
primitives to the east were tested first then the final result would be different.

If a '''linkable set''' is tested by the linkability algorithm then the final subset
of linkable parts is NOT affected by the order in which the candidates were submitted.
That is, if just the linkable subsets of the failure modes above are tested for
all permutations of sequence they will always link. The proof of this is left
as an exercise for the reader.

=== Examples ===

==== 2 very small prims ====
diameter_A = ~0.01

diameter_B = ~0.01

SMALLEST_MAX = 1.0 meters

LARGEST_MAX = 32.0 meters

max_link_distance = 1.02m

==== one large prim and one small prim ====
diameter_A = 10m

diameter_B = ~0.01

SMALLEST_MAX = 1.0 meters

LARGEST_MAX = 32.0 meters

diameter_A + diameter_B + SMALLEST_MAX = 11.01m

11.01m is smaller than 32.0m

Thus the max_link_distance = 11.01m

==== 2 very large prims ====
The diameter of a bounding sphere is the square root of x^2 + y^2 + z^2
thus, the diameter of a 10m x 10m x 10m prim is the square root of (100+100+100) = ~17.3m
and the diameter of a 10m x 1m x 1m prim is square root (100+1+1) = ~10.1m
(The type of prim doesn't matter for this calculation. We only care about the dimentions.)
Let's take the case of two 10m x 10m x 10m prims.

diameter_A = 17.3m

diameter_B = 17.3m

SMALLEST_MAX = 1.0 meters

LARGEST_MAX = 32.0 meters

diameter_A + diameter_B + SMALLEST_MAX = ~35.6m

32.0m is smaller than 35.6m

Thus max_link_distance = 32.0m

What's Changed With Havok4

2007-09-28T20:51:35Z

Sidewinder Linden: New page: ===Interpenetration Resolution=== When objects collide, they can end up "interpenetrating", in a situation where the two objects are "attempting to occupy the same space". Havok4 resolves ...

===Interpenetration Resolution===
When objects collide, they can end up "interpenetrating", in a situation where the two objects are "attempting to occupy the same space". Havok4 resolves interpenetration scenarios in a different and generally better way than Havok1.
* Interpenetration resolution is enabled for all dynamic objects
** In Havok 1 dynamic objects that started penetrating would stop colliding until they ceased to penetrate
** In Havok 4 dynamic objects will be pushed apart when penetrating

===Volume Detection===
* Volume detection is now the exact shape of the object instead of the bounding box
* Uniformly scaled spheres are implicit (roll like spheres instead of faceted blocks)
* Shapes are quantized
** The colliding shape may differ slightly from the aparent shape
** The errors should be smaller than the collision tolerance threshold, and thus not noticeable
** Shape errors would be most noticable for large objects if they are noticable at all

===Object Mass===
* llGetMass() will tend to return a larger value when an object is attached
** Attachment "mass" is estimated using a bounding box for each prim instead of the real shape

===Linkability Rules===
* [[Linkability_Rules | Link rules]] are different
** More robust: depend only on primitive position and scale (NOT rotation, cut, shear, twist, taper, or hollow)
** Larger linkability distances (proportional to sum of scales, rather than the root mean square of the sum)

===Avatar Motion===
* Avatar motion will be subtly different
** Flying/walking diagonal will not result in a speed boost
** Speed of walking up hills and ramps may be different
** Steepest hill or ramp that can be navigated may be different
** Largest step obstacle that can be climbed may be different
** Speed of walking up stairs may be different
** Run speed may be different
** Jump height and horizontal response may be different
** Acceleration/deceleration is higher when walking and stopping

===Energy===
* Energy system thresholds may be different
** Energy depends on mass of all prims in an object
** Energy of attachments are always equal to or greater than when non-attached (because of llMass() issue mentioned above)
* llPushObject() can no longer push arbitrarily hard at long distances
** The absolute largest push an object can attempt to make is determined by the size of its Energy tank (which is then attenuated based on its current Energy budget and distance^3 as per Havok1 implementation)

===Physics Engine Overload And Level Of Detail (LOD)===
* The collision level of detail (LOD) of objects may change when the physics engine lags (this is controlled by the Runtime Collision Control System (RCCS))
** At the moment there is only one LOD below the highest level: primitives collide like boxes
** Correct collision shapes will gradually return to normal when the physics engine recovers (at a rate of one prim per physics engine timestep)
** When objects transition from static to dynamic their LOD will be pre-emptively dropped and they will collide at the lower LOD until the RCCS automagically raises it
* Duplicate scripted Actions are collapsed on multi-prim objects.
** An Action is a behavior that pushes the object around, such as a Vehicle, Buoyancy, or Hover behavior.
** Making two scripts on one object each producing the same Action (such as llSetBuoyancy()) will result in a single instance of the Action instead of two
** When two scripts on distinct prims of a multi-prim object try to produce duplicate Actions from two distinct primitives and the prims are then separated in a delink operation then the single Action instance will migrate with the script that first created it; the other piece of the object will have no Action.

===Other Misc Changes===
* Vertical simulation extent has been increased from 768m to 1024m, however script and UI limitations have not yet been changed accordingly yet.

===What Is NOT Changed?===
* Dynamic objects are still limited to 31 primitives
* Most primitives still have a "collision tolerance" of 0.1 meters (everything except implicit spheres)
* Spheres with non-uniform scale will collide with faceted geometry
* Region crossing lag will not be significantly relieved by Havok4 changes
* llGetCenterOfMass() on attachments fails

===Known Bugs===
* There is a resource leak in the simulator that may cause it to crash after an extended uptime
* Avatar's don't always sit in the "right spot"
* LSL collision() events are broken
* LSL VolumeDetect feature is broken

2007-09-26T20:03:35Z

Sidewinder Linden: Live Performance/Draft/Home moved to Live Performance Home

#REDIRECT [[Live Performance Home]]

Live Performances

2007-09-26T20:03:35Z

Sidewinder Linden: Live Performance/Draft/Home moved to Live Performance Home

==Live Performance In Second Life==

===What Is A Live Performance In Second Life?===
A live performance in Second Life is presented by a person who is represented in-world by an avatar, and is creating the performance in real-time, streaming the audio (or audio and video) portions into Second Life as they are being created.

Playing back a previously recorded performance, whether audio, video or Second Life machinima, is generally not considered to be a live performance (although even this definition will likely raise some "discussion" from some corners ;).

===Types of Live Performances===
* Spoken word (poetry, fiction or other reading)
* Live musical performers (vocalists/instrumentalists with or without "backing tracks")
* Theatrical performance (plays, dramatic productions)
* Dance
* DJ/Scratch
* Other?

===Who Is Involved With Second Life Live Performance?===
* Performers [[Performance_Performer|Learn more...]]
* Second Life audience [[Performance_Audience|Learn more...]]
* Talent agents/managers/promoters [[Performance_TalentMgmt|Learn more...]]
* Venue operators [[Performance_Venue_Operators|Learn more...]]
* Sponsors [[Performance_Sponsors|Learn more...]]

===How Is Linden Lab Encouraging And Supporting Live Performance In Second Life?===
* Performance area on web site
* System features

===How Did Live Performance In Second Life Start?===
... there are probably a lot of views on this one... let's fill this in in a way that tells the story, and where we don't spend a lot of time on "no, actually i was the first", eh ;)