FAQ : HDM, huge, mega, giant prims

Quick question: if the megaprim is set to phantom and hollowed out, shouldn't you be able to enter and leave without having a door?

A friend has one at 750m and I had to use the camera sit on a prim trick to get inside. (She said that no one could get inside but her!) But I had to tp out.

Either it wasn't phantom or there's something else interfering.
I'll go check if you give me the location.

This reminds me of an interesting property that I forgot to list :
While you can't go through (non phantom) hollowed prims, you can click through their hollow.

I am currently finishing a build which includes a large (50m x 50m) lake for swimming in, although I don’t normally use megaprims, in this case it seemed a good idea in order that the animated surface of the lake did not show any join lines.
I hit a problem straight away as the only prim available was 50x50x1 which I made transparent and phantom, then applied suitable textures to the top and bottom, but when rising through the ‘surface’ there was a 1m spot where no texture was visible.

No problem I thought, and made the water level from two 50x50x1 prims separated by 0.100, applying the underwater texture to the bottom of the top prim and the surface texture to the top of the lower prim. After lots of experimenting I found that no matter how close the two textured surfaces, there was, when rising through the interface, always a 1m zone where nothing was visible.

About to give up I happened across this thread an saw that the 50x50x1 is actually a mod of the basic 50x50x50, so in one last attempt I rezzed two of them and made a 0.100 vertical gap then as before applied the textures of the bottom of the upper prim and the top of the lower. BINGO it worked to perfection and the transition from below to above water works beautifully.

It does seem a bit of overkill as my lake is now50m square and 100m deep (although only the water surface is visible), does anyone foresee problems?

A big thank you to Simil and all for an explanation of the mechanics of the megaprim.

Simil,


Go to the Hawkins sim and let me know if the sim script perf is still spiking over 115,000 ips


brief timeline of events that I've ben dealing with:

about 3 weeks ago my sim performance shot up to approx 65,000 ips

I did a search of the sim...looking at scripts and trying to figure out what was wrong. All I found was a store that was built with a bunch of 20 x 20 x .5 mega prims.

I opened a ticket to LL and told them about the high script performance. They came out and saw nothing wrong. ( )

The store disappeared and was replaced by a Marine base made with more mega prims. Still high script perf numbers.

one week ago the base was deleted and script numbers dropped back down to 20-25,000 ips.

Yesterday, script numbers shot up to around 100,000 ips so I started looking around again and noticed a new building (where the base used to be) that was built with mega prims.

I re-opened another support ticket to have the high script numbers investigated.

Last night, the owner deleted the mega prim build but the script numbers were still hovering around 115,000 ips

the sim might need to be re-booted.

I'm afraid that there is no relation.
Script performance concerns scripts, not primitives.
HDM prims would affect the simulator's FPS because of lag.
I rezzed twenty-five 20, 20, 0.5 prims in a quiet island and didn't see the IPS varying a lot.

Anybody hear back from Zero on why megaprims crank up communication costs?

So mega prims only contribute to lag in a SIM?

Here's the deal on megaprims.

There is disagreement within LL about what to do about them. There is a "destroy all megaprims" (DAMP) army in LL (of which I am Captain) and there is a "but megaprims are cool" BMPAC resistance militia which far outnumbers the army of DAMPness.

I've got some anti-megaprim nukes in my current project's sandbox and I've been making noise within LL about shipping them, but the project isn't going to get off the ground while the BMPAC controls the Governance team, QA department, and Deployment forces. As such, I've sued for a peace plan which is as follows:

Megaprims will remain in a semi-broken state indefinitely. We won't be making megaprims an officially supported feature until we can "solve them right". Solving them right means enforcing the access permissions of parcels -- preventing objects from parcel A from overlapping on parcel B if the owner of parcel B doesn't want them there. This is a Big Project, so I'm going to be breaking it up into Smaller Projects that will roll out in the following order:

(1) Death to all megaprims larger than 256 meters on a side (the BMPAC forces don't think these megaprims are cool).

(2) Allow parcel owners to manually move out or return objects that overlap their parcels.

(3) Pre-emptively disallow object placements that would violate parcel access permissions.

(4) Provide some sort of UI feedback that alerts Residents when an object placement will fail.

A semi related project that will be required by stage (2) is to give sculptie objects a better collison approximation shape.

WAIT please before you go Andrew: do megaprims in their current state, if not overlapping between sims, cause lag or other sim performance issues?

Sign me up for the BMPAC camp. Large prims have been at the top of my wish list almost as long as I've have been in Second Life.

http://tinyurl.com/2coat9

Ya im totally with you there amiee..

and as far as the problems that andrew is citing.. its basically having to do with the possiblitie of griefing with mega prims.. For those of us that use them in a logical and asthetically pleasing way we shouldnt be subjected to the Death to prim camp.

Oh btw simil ive sent you the 50x10x.01 prim.. please feel free to distrubute them as you want. they are great for building straight roads an such.

LONG LIVE THE MEGA PRIM.

TY for stopping by, Andrew! It's always nice to hear what y'all are thinking, even if there's no plan or a long range plan or a N-step plan..

Any chance you can tell us, or sneak over to his office and poke him to tell us, why Zero is in the MBCCL (mega prims can cause lag) camp??

That's good, for HDM and normal prims too.
I think that overlapping issues are caused by 2 facts :
- HDM prims are distributed tortured, with a visible size much smaller than the actual size and inexperienced residents don't realize that.
- HDM prims are too big for our needs, if we could make the HDM prims of the size we want there would be less overlapping. just having HDM prims for the standard parcel : 32, 16, 1 - 32, 32, 1 etc would be very helpful.


I talked with Flix Saiman who indeed has an HDM prim of 0.1, 10, 50
It's probably rarest one as it's not in most of the distributed packs, so thanks to him.
(You can get it from my pack that I updated.)

To me, the issue is being responsible with your megaprims, it would be easier if 1. you could autoreturn megaprims overlapping and 2. have certain building codes on the mainland specific to regions that have to do with responsible use of mega prims.

How big you can make a prim should be relative to how much continuous land is owned by you that you are building on, and ideally (probably not possible) you should be able to make prims 800m tall provided you are on your own sim and not directly bordered by a sim owned by someone else.

Would be complex to enforce that last one, but if you are willing to pony up for a sim, you should be able to do anything you want in within your borders, including making the entire thing one huge 256x256x8000 meter structure that is one prim.

Megaprims can indeed cause lag. Havok uses objects' axis aligned bounding boxes (AABB's) for its broadphase collision tests (rough collision culling). The output of the broadphase is a list of candidates which are fed to the narrophase collision tests (detailed collision results). Megaprims have such large AABB's that they will bloat the output of the broadphase forcing the more expensive narrowphase test against a very large number of objects.

Note that in Havok1 the AABB of an object is larger than you might expect. It is the cube that encloses the sphere that, centered on the object's center of mass, encloses the object for all possible rotations. So a cube 1m on a side has an AABB that is sqrt(3)~=1.732m on a side.

TY again, Andrew!

Does this bloat also apply to megaprims with phantom set?

What you're saying sounds to me like a compute drain, not a network drain. Zero seemed to be saying that megaprims near sim borders can also jack communications costs way up. Any details on that??

I don't think megaprims are expensive for the network system.

I suspect that setting an megaprim "phantom" will indeed bypass the computational drain in the physics engine. I'm pretty sure the "collision group filtering" (some groups collide with others, and some do not), which is how the "phantom" feature works, is done at the beginning of the broadphase check.

If you just *had* to have a 100x100 floor in your region, what is better: a single megaprim or 100 10x10 tiles?

It isn't all that clear in Havok1. The megaprim will cause more false positive broadphase results for activity far above it that would normally be culled for the smaller tiles, while the smaller tiles will have a larger memory footprint and more entries in the broadphase and other systematic structures.

The real problem with megaprims is the griefing possibilities and the dispute resolution issues when objects from one parcel overlap into another.

How about restricting them for private sims? i use a 65536x65536x 100 meters megasphere to build a sort of cloudy "skybox" around my sim.

The potential of griefing of these prims is greatly reduced if they are limited to estate owners.

No way, this is an unfair solution that would rise the entire mainland owners against you.
Plus it doesn't prevent HDM prims to be used for griefing on estates.

Kyrah you're showing your bad knowledge of HDM prims as there is no 65536, 65536, 100, and your irresponsibility by overlapping on a surface 65536 times (256 regions by 256 regions) wider than your land.

My friend got some giant sculpted rock mega prims for his land and we noticed that on the minimap it was actually a giant square, but on the ground you just see a big rock. The rock is phantom and I do not see how it can bother the neighbors even though according to the mini map it looks like it is on their parcels but is not. so is this okay or not? I'm really confused about the proper application of these things.

Like i said.. Mega prims lag isnt the issue that most lindens fear its the griefing .. but heres my question.. mega prims have been in SL for awhile and FREE.. and yet.. the major griefers arnt using them.. so whats the deal.. why so into the ban all of them.. Some of us use them in a respectable, logical way. What would you rather do Andrew.. use a 256 mega prim .. (in my case to totally blank out my sim for my sign) or use tons of single prims.. With those single prims I am able to increase the interest of my sim and make it just that much more interesting to the general public. Making SL more interesting and that much more popular.

I think your just tired of seeing people with mega prims over other peoples lots and making you come and pick them up.

IMO you guys should do that certification thing.. where Once your certified as an competent builder your allowed to use mega prims. anyways.. thats just my 2L on my soap box

It's not an "unfair solution". There are tons of things that private estate owners can do that mainland parcel owners cannot. That's why it costs 50% more in tier fees to own an island than to own a mainland sim. You pay for the extra benefits. Were megaprims (you seem to be the only one using the term "HDM" to be officially allowed for estate owners, it would just be one more feature on a very long list.

In RL, I live in apartment. Apartment living sucks in many ways. But you don't see me shouting at my neighbors who own houses that they're being unfair. I'm not threatening to "rise the entire apartment dwellers against" them.

The fact is LL has been talking about the possibility of allowing megaprims for estate owners since way back when megaprims first appeared on the grid. The debate over it is nothing new. You seem to be reacting though as if this is the first you've heard of it, and as if Kyrah is somehow either evil, stupid, or both, for having brought it up. That's so wrong.


And what exactly makes Kyrah's described usage of a megaprim so "irresponsible"? If she'a talking about a private island, not connected to any other sims, then what does it matter whether the prim is one sim wide or a million sims wide? It cannot affect any but hers, so who what's the big deal?

I have said that to Kyrah because he wants something for which he doesn't even show a correct understanding.

If you actually read the whole thread, you'll notice that Flix Saiman accused me of not knowing what I was taking about (but that's fine now).
None pointed out any mistake of mine as I wrote that the number of HDM prims was "17 as far as I know".
But if you can show me the 65536, 65536, 100 or even the 65535, 65535, 100 I'll just add it to the list, I have no problem with admitting and correcting my mistakes.
Using a prim insanely bigger than one's own land is irresponsible, neighbor region or not - the 1024 or 2048 would do the job perfectly.

With your reasoning the mainland owners could be deprived of all features (and only keep naked land) to the profit of island owners and it wouldn't be unfair, just because of money.
As you said the debate is not new and mainland owners have always been against it because it's highly unfair, so I don't see why you're surprised by my answer.

BTW I'm the only one to say HDM because I coined the term and because I think that it describes them properly as there could be HDM prims of 11, 11, 11 but you wouldn't say that it's huge or giant or mega.

Chosen Few if you aren't wiser and continue to argue about my attitude rather than to stay on topic, I say it again : to argue about my attitude rather than to stay on topic, I'll have your post moderated and an abuse report filled against you.
Use PM or IM for such purpose, not forums.

First, how's it irresponsible if it affects nothing and no one but the owner?

Second, how exactly do you propose a 1024 or 2048 would cover the sky from horizon to horizon, which seems to be the desired effect Kyrah was describing?


Uh, what? No, your statement does not describe my reasoning at all.

Look; here are the facts of land ownership and money:

1. Mainland owners pay a certain dollar amount for a certain set of features.

2. Estate owners pay more in order to enjoy additional features over and above what mainland owners can have.

3. Those who are "deprived of all features", as you put it, are those who don't own land, and so pay nothing.

That's perfectly fair, exactly as it should be.

Were megaprims to be added to number two there, it would hardly tip the scales very far. We all did just fine for years before megaprims existed, and we'd continue to do just as well were they to vanish tomorrow. They're kind of cool, sure, but they don't make or break anyone's SL existence.