possibly OT here: question about megaprims

Hi,


do megaprims "create lag" or not?

server-side lag? client-side? none at all?


anybody here who has some definite answers?


bye,
LC

No certain answers here. But I think I know where the myth/rumors come from. Some of this may have changed with havok 4, but I still see the problem.

Mega prims just sitting there do ok, phantom ones do even better. Where I start to see perfomance issues is when a gaggle(10 to 30) AVs are all standing on the same mega prim. Think sky store platform.
This rarely happens though. But it might be worth cosidering normal prims for objects people walk on or bump into.

Hope thar helps, and is not outdated info.

well, if you have 10 to 30 avatars standing on ANYTHING you will notice lag. It's the avatars that cause the lag, not what they are standing on. I've used full sim size floors in our elevated store for quite some time (3 sims joined). the number of prims that saves is enormous, and well worth the use of megas. as for a club type situation, not sure about this point but, when avatars are dancing on a pose, are they technically "standing" on a prim? meaning, are they interacting with the floor prim? somebody more knowledgable than me can answer that one.

True 10 to 30 avs will lag stuff. But is it realy the Avs or is it the collisions they are causing?
Bouncing back and forth between top scripts and top collision looks to show its still collisions.

So what's worse? 30 people colliding with one mega, or 30 people spread across lots of prims.
I really don't know.

The only time collisions take place is if a prim has "physics" turned on. Physical megaprims will usually cause lag on the server side.

Non-physical megaprims in moderate sizes (up to about 128m) do not cause lag. If they are near sim borders, you may see some odd visuals from next-door sims (the megaprim may not always rez, because sims only usually load objects whose center is within 10m of the sim border) -- but even that seems to be less of a problem than it used to be.

Huge megaprims, like those that Blaze uses, require a little care in use to ensure smooth sim crossings etc., but do not cause lag, in the hands of a good builder.

Be careful when using megaprims not to encroach on nearby parcels. Remember, when you cut them, their actual "size" is still the original prim size ... and thus an invisible portion of your cut megaprim can actually be overhanging and messing up your neighbor's build.
.

not entirely true... non physical megaprims still register collisions from physical objects (like avatars) based on their bounding box.

LL seems to think this cause more broad phase processing but less narrow phase, so it seemingly works out (there's a thread buried here somewhere with linden input around post 43)

it is suggested that if you use megaprims that any cuts be facing away from the side of most likely activity (so down for floors, out for walls, etc) to cut down a little on the processing.

Borrowing the words of another;



If you can use megaprims for a personal project, you should. It reduces server resources, saves on prims, and reduces the amount of polygons your computer needs to render.

They do not "create lag".

Well, thanks for all your input so far, pretty insightful stuff there.


My problem is not about building though... its about people complaining to my wife in her position as a sim owners representative, saying "that neighbour so-and-so is totally lagging up the sim with his megaprims..."


ah well.
still, enough assembled knowledge here for her to say "megaprims dont create lag unless they are physical."

the people complaining are probably causing more lag with their use of scripts and textures actually.

I`ve been on class 4 sim for several years and can not notice any real issues using mega`s . Is it a possiblity your wifes renters are misusing textures ,on the mega`s? I see some renters using mega`s as a privacy thing and have textured with transparent textures ie: tree`s and etc. i can certainly see where this could be a major lag issue . "that neighbour so-and-so is totally lagging up the sim with his megaprims..."