PBR textures are affecting Land impact?

[Eric Heartsong]

Hey, I am new in building and decoration. I created a big prim 20x10x0.5, a wall. I apply the traditionnal LH concrete 512 texture on a face. The Land Impact of my prim is 1.

I apply the PBR concrete texture I found in my viewer's library. On the same face. And the Land Impact of my prim is now 10 LI.

I investigated and I finally found that if you change some parameters such as Path cut or Hollow and you apply a PBR texture, the Land Impact explodes : one prim can have more than 100 as LI.

Does somebody know the reason?

Thanks.

[Qie Niangao]

It's not only PBR. Blinn-Phong materials have done this for years. The simple 1 LI per prim accounting is only applicable to diffusemap-only textured objects.

On the other hand, to understand what's going on you really need to check the "More info" pop-up in the Build Tool to see how the Land Impact weights are distributed. If it's Physics, you may be able to cut the LI dramatically (to 0.5, for example) by switching to Physics Type: Convex Hull. Again, though, been that way for a very long time.

[Henri Beauchamp]

8 hours ago, Eric Heartsong said:

I apply the PBR concrete texture I found in my viewer's library. On the same face. And the Land Impact of my prim is now 10 LI.

This is because your wall is not a plain wall, but is using a ”tortured prim”.

Split your wall into 3 prims (one part for the left of the door, one for the right of the door, one for above the door), then link them together, and set all of them as ”convex hulls”: the Li for a simple (non-tortured) prim is 0.5, so the total land impact for your 3 prims wall will be 1.5.

8 hours ago, Qie Niangao said:

If it's Physics, you may be able to cut the LI dramatically (to 0.5, for example) by switching to Physics Type: Convex Hull.

This won't work for a single wall prim with a door in the middle: setting it as convex hull would cause the door to be impossible to go through (because the physics ”hull” would encompass the whole prim, hole included).

[Zalificent Corvinus]

2 hours ago, Henri Beauchamp said:

Split your wall into 3 prims (one part for the left of the door, one for the right of the door, one for above the door), then link them together, and set all of them as ”convex hulls”: the Li for a simple (non-tortured) prim is 0.5, so the total land impact for your 3 prims wall will be 1.5.

A friend of mine once tried using a 128x128x0.5 megaprim to make a 1/4 sim sized platform with a hole in the middle ( prim torture hollow ), LI = 1.

Then they tried putting "materials" on it, LI = 32.

So I suggested replacing a hollowed prim with 4 stretched full perm MESH cubes, freebies off the MP. LI=1 each, total LI = 4, even with materials applied..

Another friend built a 1/10th scale prototype of a build with cut prims, LI=19, added materials, LI= 140, converted cut prims to mesh reapplied materials, LI=40 at full size.

 

11 hours ago, Eric Heartsong said:

Does somebody know the reason?

The moment you add materials to a prim, be they 10 yr old ALM Blinn-Phone or new PBR, it changes from Prim LI accounting to MESH LI accounting. sticking materials on a cut prim is BAD, don't do it.

 

[Qie Niangao]

So the other cheating way to do this is to carve up a standard prim with hollow and cuts, make it transparent, and use it as the "physics model" for the wall, then texture a duplicate with any choice materials so its Physics weight would skyrocket except you set it to Physics Type: None after linking it as a child prim of some root with trivial physics (like a little hidden cube set to Physics Type Convex Hull). The linkset gets a Land Impact of 1 and hides the "physics model" prim, also with a land impact of 1. The "cheating" part is that the "physics model" really does have a big physics impact on the sim, but honestly most regions have Havok to burn these days.

Not good if you'll be sending troops of avatars clomping around on a dozen intersecting copies of the thing, but that's a whole different building mission anyway that probably deserves a single simplified mesh physics model instead of this conglomeration of prim-based linksets.

Edited July 21 by Qie Niangao
Gah! "its" not "it's"

[Honey Puddles]

There's a feedback about this issue.. as other have said though, it's been around since ~2012.
https://feedback.secondlife.com/feature-requests/p/1-prim-should-be-1-li-even-when-it-has-a-pbr

It's definitely not predictable behaviour to have a 1Li twisted torus convert to 892Li because you added a bump map.

 

 

Edited July 21 by Honey Puddles

[BilliJo Aldrin]

I guess its a good thing I just stick to plain old ordinary textures 😂

[Theresa Tennyson]

12 hours ago, Eric Heartsong said:

Hey, I am new in building and decoration. I created a big prim 20x10x0.5, a wall. I apply the traditionnal LH concrete 512 texture on a face. The Land Impact of my prim is 1.

I apply the PBR concrete texture I found in my viewer's library. On the same face. And the Land Impact of my prim is now 10 LI.

I investigated and I finally found that if you change some parameters such as Path cut or Hollow and you apply a PBR texture, the Land Impact explodes : one prim can have more than 100 as LI.

Does somebody know the reason?

Thanks.

It's the physics weight. There are various ways around it. If nothing is going to go through a hole (i.e. window), change the physics type to "convex hull." If it's a door opening in a multi-prim structure, link it to all the other prims. An ordinary uncut box prim has a server weight of 0.5 and a physics weight of 0.1. If you link that prim to 20 other box prims you'll end up with a server weight of 10.5 and a physics weight of 12, meaning that the actual final land impact will be lower than if you just linked 21 prims with legacy accounting. (There's also "download weight" which is usually very low for prims.)

[Henri Beauchamp]

1 hour ago, Zalificent Corvinus said:

A friend of mine once tried using a 128x128x0.5 megaprim to make a 1/4 sim sized platform with a hole in the middle ( prim torture hollow ), LI = 1.

Then they tried putting ”materials” on it, LI = 32.

So I suggested replacing a hollowed prim with 4 stretched full perm MESH cubes, freebies off the MP. LI=1 each, total LI = 4, even with materials applied..

In fact, they would have had way better results with four 64mx64mx0.5m prims linked together and converted to ”convex hulls”: LI = 2 ”only”...

The LI system does help increasing the number of prims you can rez on any given parcel, on the condition to use it wisely (and yes, this can be uselessly tricky, due to server bugs: see my next post).

Edited July 21 by Henri Beauchamp

[Henri Beauchamp]

1 hour ago, Honey Puddles said:

It's definitely not predictable behaviour to have a 1Li twisted torus convert to 892Li because you added a bump map.

I indeed consider this a bug in the LI conversion system: most of the times, when you want to convert an old build to the LI system (be it to add materials, ALM or PBR alike, or to try and lower the total impact of a build), you must be very careful (I recommend doing it in a sandbox, where you do not risk things returned to your inventory due to parcel prims count overshoot), and must always start with converting the root primitive to ”convex hull” (*), else the bug will creep in and get your LI to skyrocket absurdly high !

Then, edit each child prim in turn, and when they are not tortured prims, convert them to ”convex hull”, or even better (not so much for LI than for the physics engine performances in your sim),  when they do not contribute to the physics of the build (i.e. collision with them is not an issue), to ”none”.

----

(*) And should the root primitive be a tortured prim, then first change it for a simple transparent cube (i.e. add one such cube as the root of your object) !

Edited July 21 by Henri Beauchamp

[Theresa Tennyson]

23 minutes ago, BilliJo Aldrin said:

I guess its a good thing I just stick to plain old ordinary textures 😂

Sure, if you want your prim build to be twice the land impact that it could be.

I've built a lot of buildings out of mostly prims lately. The vast majority came out as half the land impact that they would be if I used the old accounting, even with hollow prims and various other whatnot. Most of the real high-land-impact modified prims can have their physics type set to "none" and they'll be down to their original server and download weights.

[Henri Beauchamp]

17 minutes ago, Theresa Tennyson said:

Sure, if you want your prim build to be twice the land impact that it could be.

Not twice, in practice (due tortured prims and the fact that in the LI system, the prim size is taken into account), but you can easily gain 20% of your land impact usage with such conversions, when all your builds are prim-based and you convert them to the LI system.

You can also ”exploit” the fact that LI are decimal numbers with 5/5 rounding (i.e. 1.49 LI object = 1 LI accounted in the parcel, while an 1.50 LI object = 2 LI accounted), to group (link) objects together, depending on their LI, to have the largest amount of them closest to a X.49 LI, meaning you gain 1 prim/LI per object.

Edited July 21 by Henri Beauchamp

[BilliJo Aldrin]

30 minutes ago, Theresa Tennyson said:

Sure, if you want your prim build to be twice the land impact that it could be.

I've built a lot of buildings out of mostly prims lately. The vast majority came out as half the land impact that they would be if I used the old accounting, even with hollow prims and various other whatnot. Most of the real high-land-impact modified prims can have their physics type set to "none" and they'll be down to their original server and download weights.

1 li for 1 prim is good enough for me, thank you though.

The most I do with prims is hollow them out, or cut them, their Li is still 1 though.

😁

[Zalificent Corvinus]

2 hours ago, Henri Beauchamp said:

In fact, they would have had way better results with four 64mx64mx0.5m prims linked together and converted to ”convex hulls”: LI = 2 ”only”...

I'm sorry but that is in fact, wrong.

1. They wanted a 3m x 3m hole in the 1/4 sim sized slab. Since you cant cut a small 1.5m x 1.5 m piece out of the corner of a prim, you'd have to use 6 prims, 4 large slabs, and two narrow strips. LI = 6

2. Back then the MAX distance between the centres of links in a link set was 54m, so you CANNOT link all the prims together, convex hulled or not, and unlinked, a convex hulled prim's ).5 LI is rounded up to 1 L:I each, so total LI at best for your 6 prims would be 4 so no real benefit.

3. Even today when max link distance is 64m, you could only link 3 of the 4 prims together, so3 x 0.5 = 1.5, rounded to 2, plus o.5 rounded to 1, means LI = 3, unless you made TWO 2-prim linksets, with LI = 1 each. But that's aa recent change. Back then, 4 mesh blocs was the way to go.

[Henri Beauchamp]

52 minutes ago, Zalificent Corvinus said:

They wanted a 3m x 3m hole

I'm afraid I did not read this properly... With a hole in the corner, it is more complicated, yes...

But:

52 minutes ago, Zalificent Corvinus said:

They wanted a 3m x 3m hole in the 1/4 sim sized slab. Since you cant cut a small 1.5m x 1.5 m piece out of the corner of a prim, you'd have to use 6 prims, 4 large slabs, and two narrow strips. LI = 6

If I understand you well, they only need two prims:

+-------------+
|             |
|             |
|             |
+--+~~~~~~~~~~|
   |          |
   +----------+

The ”~~~~~” represents the place where you need to ”split” the initial platform into two (non-tortured) prims: only two rectangles are needed to ”cut a small 1.5m x 1.5 m piece out of the corner of a prim”...

If you want to cover 128x128m, you need three more 64x64m prims around the North & East borders, and North East corner (meaning 5 prims in total), but this is due to the fact your friend used a mega-prim, and I am not even sure that, today, you still can torture such a prim without having it snapping back at the max 64x64m size....

Edited July 21 by Henri Beauchamp

[Theresa Tennyson]

3 hours ago, BilliJo Aldrin said:

1 li for 1 prim is good enough for me, thank you though.

The most I do with prims is hollow them out, or cut them, their Li is still 1 though.

😁

If you'd set them to "convex hull" or "none" they'd be 0.5 each, but you be you...