User:Andrew Linden/Office Hours/2008 02 05

Transcript of Andrew Linden's office hours:

[11:02]	Arawn Spitteler:	I've an idea for a circular bench, that grows with occupation, but have to figure how to turn people about.
[11:02]	Teravus Ousley:	Hello everybody :D I'm actually in two meetings unfortunately ;P
[11:02]	Arawn Spitteler:	I think I just solved it, though.
[11:02]	Kitto Flora:	Hello Andrew
[11:02]	Andrew Linden:	Hi everybody.
[11:02]	Teravus Ousley:	Hello :D
[11:03]	Anders Falworth:	Hi, Andrew
[11:03]	Ruud Lathrop:	Hi
[11:03]	Rex Cronon:	hi
[11:03]	Arawn Spitteler grovels politely in the discretely general direction of our new arrival
[11:03]	Andrew Linden:	I'm in a bad mood today, because I've been trying to fix @#$%^& avatar motion bugs
[11:03]	Andrew Linden:	that code is going to be the death of me
[11:04]	Arawn Spitteler hopes he isn't serious, about catching his death of Code: Live by hte sword, and all
[11:04]	Rex Cronon:	u should buy a punch bag. helps u releave stress:)
[11:04]	Kitto Flora:	Whats buggy about avatar motion?
[11:04]	Ruud Lathrop:	Or grap a gun and go shoot somebody in SL :)
[11:05]	Teravus Ousley:	yes, or a pillow .. or at least a fax machine that you can bash in the parking lot
[11:05]	Andrew Linden:	we have a new update, held up by some last minute QA stuff going on right now
[11:05]	Andrew Linden:	hopefully today
[11:05]	Rex Cronon:	yes, go to a fighthing sim and create havok:)
[11:05]	Ruud Lathrop:	new update of server?
[11:05]	Andrew Linden:	yeah, new Havok4 preview update
[11:06]	Andrew Linden:	There will also be a viewer update sometime after that, in a few days
[11:06]	Andrew Linden:	but it is pending some MONO compatibility UI stuff
[11:06]	Kitto Flora:	Hi Simon
[11:07]	Simon Linden:	Hi folks
[11:07]	Ruud Lathrop:	Hi
[11:07]	Rex Cronon:	hi simon
[11:07]	Anders Falworth:	Hi, Simon.
[11:07]	Rex Cronon:	interesting, we have a mole here:)
[11:07]	Teravus Ousley:	Hello
[11:07]	Andrew Linden:	the stuff in the next Havok4 update was all stuff that was done last week
[11:08]	Andrew Linden:	so nothing new to report that will be in the update
[11:08]	Arawn Spitteler:	STATUS_ROTATE?
[11:08]	Andrew Linden:	what is NOT in the update are things such as the STATUS_ROTATE fix
[11:09]	Andrew Linden:	I fixed one of Cubey Terra's planes (the ultralight). NOT in the update
[11:09]	Andrew Linden:	And while I was at it I convexified the collision proxies for sculpy prims
[11:10]	Andrew Linden:	they were being proxied by tori
[11:10]	Rex Cronon:	what does that mean? i am talking about sculpties.
[11:10]	Andrew Linden:	but will eventully be convex hull's of tori
[11:10]	Andrew Linden:	Well, at the moment sculpties don't collide anything like their apparent shape
[11:10]	Rex Cronon:	yes, i know is torus
[11:10]	Andrew Linden:	the collide and roll around like a regular default torus, with scale
[11:11]	Andrew Linden:	but the torus uses the Havok "mesh shape" which is kinda CPU expensive
[11:11]	Andrew Linden:	and sculpties are usually used for their collision properties
[11:12]	Andrew Linden:	so instead of using the mesh shape I use the "convex vertices shape" (basically a convex hull)
[11:12]	Andrew Linden:	which is cheaper
[11:12]	Andrew Linden:	and still kinda rolls around like the torus (but with the hole filled in)
[11:12]	Arawn Spitteler:	So, Stairs won't need their invisible ramps?
[11:12]	Rex Cronon:	so now basically sculpties are ovals?
[11:13]	Andrew Linden:	no, stairs may still need their invisible ramps
[11:13]	Andrew Linden:	sculpties still won't collide like their apparent shapes
[11:13]	Andrew Linden:	but the shape the DO use will cause less lag
[11:13]	Nitram Wei:	Script run-time error
[11:13]	Nitram Wei:	Too Many Listens
[11:13]	Teravus Ousley:	always a positive :D
[11:13]	Andrew Linden:	yeah, they are kinda egg shaped... but symmetrical, no fat end
[11:14]	Rex Cronon:	elyptical?
[11:14]	Arawn Spitteler thinks the lack of a fat end is why we can't open them
[11:14]	Rex Cronon:	hi nitram
[11:14]	Andrew Linden:	I had some subject that I was going to raise for discussion... but I've forgotten what it is.
[11:14]	Nitram Wei:	hi
[11:14]	Andrew Linden:	Hello Nitram, welcome.
[11:14]	Nitram Wei:	thnx
[11:15]	Andrew Linden:	oh yeah, I remember one thing...
[11:15]	Teravus Ousley:	Kind of like that.. ---> Points to the prim on the table
[11:16]	Andrew Linden:	A Resident named Areth Gall contacted me because he had been measuring the moments of inertia of hollow boxes
[11:16]	Andrew Linden:	and was coming up with numbers that did not match the theoretical values
[11:16]	Andrew Linden:	so when I looked into it... sure enough there was a bug
[11:16]	Andrew Linden:	so I fixed it (NOT in the update, but few would notice anyway)
[11:17]	Andrew Linden:	and was pleased that I've got such intrepid Residents out there testing stuff.
[11:17]	Rex Cronon:	they had too much mass?
[11:17]	Andrew Linden:	well... too much angular mass
[11:18]	Andrew Linden:	all of the diagonal elements of the inertia tensor were too large by 0.01
[11:18]	Arawn Spitteler:	That sounds rather precise
[11:18]	Andrew Linden:	really not very noticable... maybe 16% too big for a default cube
[11:19]	Andrew Linden:	yes, it was very precise. Turns out the default inertia was set to the identity before adding up the parts
[11:19]	Andrew Linden:	and there is a mysterious factor of 1/100 related to the discrepancies between the new "real" mass and the "legacy" Havok1 mass that you get when you call llGetMass()
[11:20]	Arawn Spitteler:	How do you measure "real" mass?
[11:20]	Andrew Linden:	well, you can multiply the legacy mass by 100
[11:21]	Andrew Linden:	but it is only used internally (in the physics engine) at the moment
[11:21]	Andrew Linden:	I'm not interested in adding a llGetRealMass()
[11:21]	Arawn Spitteler wonders how the measurement was done.
[11:21]	Andrew Linden:	but maybe someday when we have LSL3 or whatever we can move toward more realistic masses
[11:22]	Arawn Spitteler:	So GetRealMass()= llGetMass()*100;
[11:22]	Andrew Linden:	How would you measure the moments of inertia of an object in SL? Anyone know?
[11:22]	Rex Cronon:	i thought that lsl will be replaced by mono
[11:22]	Andrew Linden:	MONO will initially have the same LSL interface... you'll still write in LSL
[11:22]	Andrew Linden:	but the execution under the hood is different
[11:23]	Arawn Spitteler:	I know that Rotational Inertia is the sum of mass* radius squared
[11:23]	Andrew Linden:	but what if someone were to write LLPython that uses different syntax
[11:23]	Rex Cronon:	but eventually u should be able to use c#, c++, java, or other languages
[11:23]	Andrew Linden:	and maybe different callback structure
[11:23]	Andrew Linden:	Yes Arawn, it is the integration of mass * radius^2, over the object's volume
[11:24]	Domchi Underwood:	Hi everyobdy...
[11:24]	Ruud Lathrop:	Hi
[11:24]	Rex Cronon:	hi domchi
[11:24]	Andrew Linden:	so for complicated objects the integral is messy
[11:24]	Andrew Linden:	it is often easier to just measure it
[11:24]	Rex Cronon:	.
[11:25]	Arawn Spitteler:	I think there's something about adding the Moments of Inertia, of each prim, as factored somehow by the square of that prim's radius. Generally, you'd llGetTargetOmega before and affter llApplyRotationalImpulse
[11:25]	Andrew Linden:	that is right Arawn
[11:26]	Andrew Linden:	In SL you can give the object hover so that it doesn't hit anything
[11:26]	Andrew Linden:	then apply angular impulses and measure the angular acceleration
[11:26]	Andrew Linden:	F = ma is the linear equation
[11:27]	Andrew Linden:	torque = inertia * angular_velocity is the angular equivalent
[11:27]	Andrew Linden:	however, the inertia is actually a tensor, but if you're spinning about one cardinal axis then it collapses into a scalar equation
[11:27]	Arawn Spitteler:	Angular Acceleration could get complicated
[11:27]	Andrew Linden:	and you can just measure each axis by itself
[11:28]	Andrew Linden:	The legendary Xylor Bayslef was the first person I knew of to measure the inertia tensors in that way.
[11:29]	Ruud Lathrop:	What are the major bug fixes in this release?
[11:29]	Andrew Linden:	lemme look them up...
[11:29]	Arawn Spitteler:	So, if this table were set Physical Hover, it would gain speed, each time one of us dismounted?
[11:30]	Kitto Flora:	It has no rotational speed
[11:30]	Kitto Flora:	cchange the sizze - still no r-speed
[11:31]	Andrew Linden:	first of all, the next update will bring Havok4 up to par with the recently released 1.19.0 server
[11:31]	Simon Linden:	The hover calculations use the current mass and are applied in each timestep, so changing the mass won't make it rise or fall
[11:31]	Andrew Linden:	There were a few small performance optimizations... I expect them to be measureable in a few content scenarios, but not very big.
[11:32]	Andrew Linden:	There was a duplication of selection not lining up bug that as fixed
[11:33]	Andrew Linden:	I tried to fix SVC-1089 and failed
[11:34]	Andrew Linden:	SVC-1239 is fixed (llSetLinkPrimitiveParams() on avatar) was breaking some boats and other things
[11:34]	Andrew Linden:	I'm hoping SVC-1272 (boats too low in water) is actually fixed
[11:34]	Domchi Underwood:	Andrew, I read your plan on megaprims... but can you comment on microprims? Will some action be taken regarding them?
[11:34]	Andrew Linden:	oops... I take that back
[11:35]	Andrew Linden:	I wasn't watching the revision numbers carefully and looked over where we stopped for this update
[11:36]	Andrew Linden:	sigh... which means everything since SVC-1089 is NOT fixed in this update
[11:36]	Gaius Goodliffe:	Hmm... Andrew, is SVC-1089 possibly related to other "dropping like a rock" issues, like, for example, how when flying at 640m, if you press forward, you drop like a rock?
[11:36]	Andrew Linden:	the dropping like a rock issue is fixed
[11:36]	Andrew Linden:	and is not related
[11:36]	Gaius Goodliffe:	oh cool.
[11:37]	XerxesTiny.LITTLE BEE.Head:	Touched.
[11:37]	Ruud Lathrop:	If a bug is 'fix pending' will that mean they are being released in next server/client update?
[11:38]	Andrew Linden:	sigh... I'm just not in the mood to read the logs and figure out where one update started and another ended
[11:38]	Andrew Linden:	do you remember anything Simon?
[11:38]	Simon Linden:	Ruud - it may not be the immediate next update. It depends on when it was fixed vs. when we built and start testing the update
[11:38]	Andrew Linden:	most of the stuff we announced as in the next update on Thursday is in this one
[11:39]	Simon Linden:	I'm not sure of the cutoff either ... I think most of what's about to go out was discussed Thursday
[11:39]	Ruud Lathrop:	Ok
[11:39]	Sascha Vandyke:	is an update version scheduled already ?
[11:40]	Arawn Spitteler:	So, how soon is a certain Cabriole ready for a test drive?
[11:40]	Simon Linden:	I do know I'm currently working on a vehicle bug, where it's going wildly out of control. I'm not sure how many vechicles it affects
[11:40]	Andrew Linden:	the update should happen today if all goes well
[11:40]	Sascha Vandyke:	ahh ok
[11:41]	Sascha Vandyke:	is there any blog to find the time or announcement
[11:41]	Andrew Linden:	no the blog announcement would go out after the update has happened and the beta is open
[11:41]	Sascha Vandyke:	ahh ok thx
[11:41]	Andrew Linden:	so you can tell when it is happening when the beta grid goes down
[11:42]	Andrew Linden:	but this update will also go out to any regions on the main grid that are using Havok4
[11:42]	Andrew Linden:	hrm... I wonder if they'll do that tomorrow or today
[11:42]	Andrew Linden:	Sidewinder knows.
[11:42]	Kitto Flora:	This is 1.18.6.78103
[11:42]	Sascha Vandyke:	thx
[11:43]	Kitto Flora:	so when he 78103 is a larger number, then you are on a new h4 server version
[11:44]	Domchi Underwood:	Andrew, I have a question re your megaprim genocide plan. ;)
[11:44]	Andrew Linden:	ok ask
[11:45]	Domchi Underwood:	What about microprims... any plans about them?
[11:45]	Andrew Linden:	No microprims for a while.
[11:45]	Andrew Linden:	Er... no plans.
[11:45]	Andrew Linden:	The physics engine has a "collision tolerance" of 0.1 meter
[11:45]	Sascha Vandyke:	will also the 256x256 be gone? lol that would interest me personally
[11:45]	Brookston Holiday:	Megaprim genocide plan?
[11:45]	Domchi Underwood:	:) But eventually, will they have to go as well?
[11:45]	Domchi Underwood:	The plan to get rid of megaprims. :)
[11:46]	Andrew Linden:	objects smaller than that,or on that scale, will not collide very accurately
[11:46]	Andrew Linden:	There is no Megaprim genocide plan
[11:46]	Andrew Linden:	however... that reminds me...
[11:46]	Andrew Linden:	I think Kelly fixed a megaprim link bug with a hack to the linkability rules
[11:46]	Gaius Goodliffe:	w00t!
[11:46]	Andrew Linden:	so someone here had a blimp that did not link
[11:46]	Andrew Linden:	I believe that has been fixed
[11:47]	Simon Linden:	Yes, that was fixed ... I confirmed it
[11:47]	Gaius Goodliffe:	That was me. :D
[11:47]	Andrew Linden:	Here is the plan for megaprims...
[11:47]	Rex Cronon:	so any prim that is within 10m can be linked?
[11:47]	Andrew Linden:	(1) make it so parcel owners can return (or maybe just move?) objects that are overlapping their parcels
[11:48]	Andrew Linden:	(2) provide some UI feedback to builders when their objects extend outside of their allowed building boundaries
[11:48]	Gaius Goodliffe:	(I don't know if "just move" would work -- what if the megaprim is bigger than the owner's parcel? (thinking of First Land plots (and dating myself, I guess lol)))
[11:48]	Andrew Linden:	(3) give parcel owners some more options for automatic enforcement of their boundaries (off by default)
[11:49]	Ruud Lathrop:	That can also be applied to normal prims?
[11:49]	Andrew Linden:	(4) allow builders to build any size (and sometimes only as large as can fit on their parcel) AKA "megaprim liberation"
[11:49]	Gaius Goodliffe:	That would be very nice. :D
[11:50]	Andrew Linden:	yes, steps (1) throuth (3) are just about normal prims
[11:50]	Andrew Linden:	after that, Megaprims can be considered normal prims
[11:50]	Andrew Linden:	there are a few details in there...
[11:50]	Andrew Linden:	sculpties are difficult to query for parcel overlap
[11:50]	Andrew Linden:	so that is it own kinda big project
[11:50]	Sascha Vandyke:	ok what about a private estate with some parcels and i want a megaprim going over them
[11:51]	Andrew Linden:	btw... that is NOT the official LL plan on megaprims
[11:51]	Andrew Linden:	that is MY plan
[11:51]	Sascha Vandyke:	ahh ok lol
[11:51]	Andrew Linden:	I'm the only one with a plan on megaprims
[11:51]	Andrew Linden:	unfortunatly, I'm trying to finish Havok4 first
[11:51]	Rex Cronon:	don't sculpties have a bounding box?
[11:52]	Andrew Linden:	yes sculpties do have a bounding box, but it is not accurate
[11:52]	Teravus Ousley:	up to twice the radius that the sim currently knows about
[11:52]	Teravus Ousley:	and that's radius in terms of an ellipsis
[11:52]	Andrew Linden:	so as soon as you start trying to enforce prim encroachment then sculpties will be one of those corners of the possibility space that do not follow the expected rules
[11:52]	Teravus Ousley:	:D
[11:53]	Andrew Linden:	also... there is the problem of prims overlapping into neighboring regions
[11:53]	Andrew Linden:	that is harder to solve for the encroachment problem
[11:53]	Andrew Linden:	so that is its own kinda big project
[11:54]	Andrew Linden:	I describe my megaprim plan every other week in office hours nowadays
[11:54]	Ruud Lathrop:	:)
[11:54]	LuckySweet Kondor:	o.o walked in on somthing i see
[11:54]	Domchi Underwood:	And you also did on forums and blog... :)
[11:55]	Arawn Spitteler:	Mega-Sculpties will be nice, but their appearence shouldn't be allowed to damage their repute
[11:55]	Gaius Goodliffe:	prims of ill-repute? o.O
[11:55]	Andrew Linden:	I was thinking I'd like to work on making better collision approximations for sculpties
[11:56]	Domchi Underwood:	Ah, forums are working again... here's the link to original post Andrew wrote:
[11:56]	Domchi Underwood:	http://forums.secondlife.com/showpost.php?p=1667877&postcount=33
[11:56]	Andrew Linden:	however recently I ventured into the simulator side code for sculpties (for the convexification project I was mentioning earlier today)
[11:56]	Andrew Linden:	and now I don't want to touch the sculptie code with a 10-foot pole
[11:57]	Teravus Ousley:	heh
[11:57]	Arawn Spitteler:	A ten foot pole wouldn't be Sculpty or Maga
[11:57]	Andrew Linden:	I might even rather fix vehicle and avatar motion bugs than try to work on sculpties
[11:57]	Teravus Ousley:	hehe
[11:58]	Gaius Goodliffe:	lol
[11:58]	Sascha Vandyke:	is better yes, i have found a lot of av bugs lately lol
[11:58]	Teravus Ousley:	the texture would be a property of the sculptie that would have to be 'stored with' the sculptie instead of requested on demand.. and you'd have to decode the image and generate a convex mesh from it.
[11:58]	Rex Cronon:	what did u find there that scared u so much:)
[11:59]	Teravus Ousley:	a scary proposition.. with lots of math
[11:59]	Andrew Linden:	it turns out the simulator doesn't know much about sculpties
[11:59]	Harleen Gretzky:	Then there is also animated sculpties to worry about
[12:00]	Andrew Linden:	but prims have a general purpose container for holding some "extra data"
[12:00]	Teravus Ousley:	lol, the idea of a body having to be rebuilt with an animation is @.@
[12:00]	Andrew Linden:	it is currently used for flexi, sculptie, and something else that I can't remember
[12:00]	Gaius Goodliffe:	I've always had the impression that sculpties were pretty much spheres with some interesting client-side drawing behavior...
[12:00]	Andrew Linden:	the interface to that extra data container is terrible (a mix of bad C and bad C++)
[12:00]	Teravus Ousley:	knowing what a change does to a physical body that interpenetrates something.. essentially 'explode kaboom'
[12:01]	Teravus Ousley:	like what happens when you unlink physical prim
[12:01]	Teravus Ousley:	:D
[12:01]	Andrew Linden:	right Gaius, so atm the simulator doesn't know much about the sculptie status
[12:01]	Andrew Linden:	it doesn't yet download the textures itself
[12:01]	Gaius Goodliffe nods.
[12:01]	Andrew Linden:	but it would have to in order to generate the collision mesh
[12:02]	Andrew Linden:	or else we'd have to provide the collision mesh in some other way
[12:02]	Andrew Linden:	in fact, there is very little sculptie specific code in the simulator
[12:02]	Andrew Linden:	since it goes through a general purpose container
[12:03]	Andrew Linden:	but that general purpose container is just poorly implemented and I phear it
[12:03]	Roxanne Hynes:	Are there plans on completely removing some of the Megaprims, for example prims that are equal or go above 256x256? Or will nothing change for now with that?
[12:03]	Gaius Goodliffe:	hehe
[12:03]	Andrew Linden:	sorry, yes Roxanne. megaprims with sides > 256 will have their sides clamped to 256
[12:03]	Gaius Goodliffe:	Awww
[12:03]	Sascha Vandyke:	ahh then is fine
[12:03]	Roxanne Hynes:	ok thanks
[12:04]	Andrew Linden:	not exactly megaprim genocide, but definitely targeted murder
[12:04]	Teravus Ousley:	yeah, at this point, there's not a lot of good uses for megaprim beyond that size
[12:04]	Sascha Vandyke:	is there anything you noticed from havok 4 playing together with the new server code?
[12:04]	Arawn Spitteler:	I think it depends on whether you've more than one sim
[12:04]	Simon Linden:	Sascha - you mean moving from one sim to another?
[12:04]	Gaius Goodliffe:	Extropia Core has a good use for them -- check out their "low earth orbit" stuff if you're ever there. I think they use a 1024x1024x100 one to make it happen, though.
[12:05]	Sascha Vandyke:	yes, and some more lag now, think it has become worse after introducing 1.19 to the main
[12:05]	Sascha Vandyke:	i have avs coming to my sim and they just don't load sometimes
[12:06]	Simon Linden:	I haven't heard of any specific problems, but the next version we push out will be based on 1.19
[12:06]	Sascha Vandyke:	ahh ok
[12:06]	Simon Linden:	... meaning up-to-date; we try to pick up any bug fixes that are pushed with the normal server so we don't fall behind
[12:07]	Kitto Flora gusses: If you have an island sim and you put a 1024x1024 megaprim on it, and plaint it, you can make ground or sky scenery that extends further than the edge of the sim... effectivly to the horizon.
[12:07]	Sascha Vandyke:	ok thx. I also have the problem to report some bugs, jira is not so nice to find bugs for havok4, i already reported twice a double one
[12:08]	Andrew Linden:	Yeah, the bugs are piling up there.
[12:08]	Gaius Goodliffe:	Kitto: right. In Extropia they use one up high so you see a curved earth beneath you while you're in orbit.
[12:08]	Andrew Linden:	I'm going to try to make a pass and close some of the Havok4 bugs in the public jira
[12:08]	Harleen Gretzky:	How do you gus? as in [12:07] Kitto Flora gusses: If...
[12:08]	Sascha Vandyke:	would be nice
[12:09]	Kitto Flora:	SVC-1093 was fixed a while back, still shows open
[12:09]	Kitto Flora does /me guesses
[12:09]	Gaius Goodliffe guesses you should use /me. :)
[12:09]	Harleen Gretzky:	ahh
[12:09]	Andrew Linden:	I've got to go now, so we'll have to wrap up.
[12:10]	Sascha Vandyke:	have a nice day
[12:10]	Ruud Lathrop:	Ok
[12:10]	Teravus Ousley:	Good luck with the avatar movement, sir
[12:10]	Arawn Spitteler has heard some debate, on whether Megaprims lag the sims
[12:10]	Ruud Lathrop:	All have a nice night :)
[12:10]	Teravus Ousley:	:D
[12:10]	Kitto Flora:	We await the update with baited bugtraps.
[12:10]	Rex Cronon:	bye everybody, i have to go to
[12:11]	Simon Linden:	Thanks everyone
[12:11]	Teravus Ousley:	take care :D