Uploading Physics Model as File

[Wulfie Reanimator]

Even doing the physics in a pretty "wrong" way gets you surprisingly low LIs. Here, every straight section of a wall is its own "cube."

A doorway has around 3 cubes surrounding it. The sides, and the top. Each cube has all of its 6 sides, so that's 12 tris per cube. 20 separate cubes in total (excluding floor). Everything is convex.

Now to do things a bit more properly:

We can get rid of 36 tris just by removing the physics shape on top of the 3 doorways, who needs that anyway, are you walking on the ceiling? (Maybe you are, you decide what's important.) While we're at it, let's remove all the faces that are inside of other walls, including the undersides of the walls and the floor. Those aren't needed because nothing can/should ever collide with them.

Physics cost already dropped from 6.0 to 2.3. From 240 triangles to 154. (Including floor, now.)

Note: You don't need a physics shape for the windows, unless you plan on jumping out of one. I also stretch the planes as far out as I can instead of properly connecting the walls into each other, because it would just increase complexity. Just clip those planes into each other, no problem. Rezzing works fine, raycast works fine, my avatar doesn't hover any more than anywhere else.

Edited August 27, 2020 by Wulfie Reanimator

[Extrude Ragu]

what kind of black magic voodoo is going on there to get such low LI with a physics shape that has more tri's than a cube? every time i've ever had to upload a model with an even slightly complex physics shape it has increased the cost significantly

[ChinRey]

46 minutes ago, Extrude Ragu said:

what kind of black magic voodoo is going on there to get such low LI with a physics shape that has more tri's than a cube? every time i've ever had to upload a model with an even slightly complex physics shape it has increased the cost significantly

For analyzed physics made entirely from cubes, there is no black magic voodoo at all. Each cube adds 0.360 to the physics weight, nothing more and nothing less. The number of tris don't matter for analyzed physics at all because the uplaoder eliminates them all and only retains the shape.

Unanalyzed physics is a different matter though. The number of tris does matter there (although not as much as you may think) and you could probably get the physics weight for Wulfie's example house even lower that way. But that can sometimes take a little bit of experience and knowledge - or black magic voodoo if you like.

I son't have an exact match for Wullfie's example but here's a house (or rather the first floor of a house) made with unanalyzed physics. It only has four rooms whereas Wulffie's has seven but it has two exterior doors and includes the floor, foundation and a ceiling with a stairwell. Yet the physics weight is only 1.5:

But with that being said, getting the physics weight down for a house shouldn't be that important. After all it's only the highest of the three weights that counts as the land impact and if a hosue has a physics weight higher than its downlaod weight, there's bound to be something seriously wrong with it anyway.

[Wulfie Reanimator]

3 hours ago, ChinRey said:

Unanalyzed physics is a different matter though. The number of tris does matter there (although not as much as you may think) and you could probably get the physics weight for Wulfie's example house even lower that way. But that can sometimes take a little bit of experience and knowledge - or black magic voodoo if you like.

I genuinely can't tell if you know this, but my example is not analyzed.

4 hours ago, Extrude Ragu said:

what kind of black magic voodoo is going on there to get such low LI with a physics shape that has more tri's than a cube? every time i've ever had to upload a model with an even slightly complex physics shape it has increased the cost significantly

I wouldn't call it expertise or black magic, I deliberately did everything as hastily/lazily as I could. I kept duplicating a cube and moving it to where I wanted the wall to be, then just joined everything into one.

Edited August 28, 2020 by Wulfie Reanimator

[ChinRey]

Just now, Wulfie Reanimator said:

I genuinely can't tell if you know this, but my example is not analyzed.

No, I didn't realize that. I shuold have noticed but I was too lazy to do the math.

 

[animats]

Basic house, in Blender. One mesh piece. No trickery at all. Solid walls, beveled connection at the corners, door cutout.

Convex decomposition. Extra contrast in the display window.

Now, this is almost perfect. The convex decomposer got all the right hulls, except for the left side, which was split into two triangles.

Exported with Blender SL static defaults. Same model used for all LODs and physics. Analyzed "solid" physics, no "simplify". 3 LI.

Next, analyzed "surface" physics.

 

[animats]

Uploading in "surface" mode. This, too, generates convex hulls. This time, 6 instead of 7. It's followed the original geometry more closely. The joints between the sides are beveled, and the hulls match that.

That's as good as it can get for this model. Incidentally, the image above has been contrast-enhanced so you can see what's going on. The upload window is trying to show the convex hull pieces as translucent, and the image is just too dim.

 

In world. 2 LI. Getting from 7 hulls to 6 brought us down by one LI, as it should. 0.360 LI per hull, as Chin Rey points out.

So this is the "house and door" problem done in a straightforward way. One big mesh for the whole object, with correct geometry in Blender. No duplicate vertices, no interior faces. Given clean geometry, the uploader seems to be able to do the right thing.

Files for this example:

• http://www.animats.com/sl/misc/basichouse04a.blend
• http://www.animats.com/sl/misc/basichouse04a.dae