Basic question about Mesh primcount

[Lupo Ellison]

Just uploaded a hollowed octagon.

In the menu edit build I read:

1 object (1 prim, 49 prim equivs) selected.
Physics wheight 48,7 - Render cost 70

I rezzed it at my enabled for Mesh sim (Magnum server), and saw in about land that the primcount of the item seems to be = 49

If I properly understood, is the primcount of a Mesh in the words:  "49 prims equivs" ?

So for example if a person has a 1024 land with 234 prims available, after rezzing the octagon, as swimmingpool maybe, more then 1/5 of the available prims are gone. 

[Gaia Clary]

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Lupo Ellison wrote:

Just uploaded a hollowed octagon.

In the menu edit build I read:

1 object (1 prim, 49 prim equivs) selected.

Physics wheight 48,7 - Render cost 70

 

I rezzed it at my enabled for Mesh sim (Magnum server), and saw in about land that the primcount of the item seems to be = 49

If I properly understood, is the primcount of a Mesh in the words: 

 "49 prims equivs"

 ?

So for example if a person has a 1024 land with 234 prims available, after rezzing the octagon, as swimmingpool maybe, more then 1/5 of the available prims are gone. 

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Since the PE is calculated from the MAXIMUM of the three values "Physics weight", "Server weight" and "Upload weight", in your case it is the physics weight which makes the trouble.

The easiest way to step out of this problem is by given your object a custom physics shape during upload. If your object not even needs physics at all, you can get away with something very simple, like just a triangle for example. then the physics costs go down to near zero and now either the "Server Weight" or the "Upload Weight" will rule the PE.

If you need physics on your object, consider to use a minimal shape like for example just the objects bounding box. You can use a siple cube (8 vertices, 6 quads ) for example. As far as i can tell, it will be automatically adjusted to scale to the true bounding box. So you could make a "one fits all" minimal physics shape for all your future mesh projects...

Another approach would be to go to the physics tab, there select "create physics shape from "LOWEST" LOD...

And finally you could simply create a linkset where the base object is a simple invisible cube and the mesh is a child of the cube. Then disable physics on the mesh and you get the physics cots of the cube (which is not as low as it would be if you probvided your own bounding box as explained above).

You see, you have many possibilites to get your PE realy down ;-)

[DanielRavenNest Noe]

A hollow octagon should be nowhere near 49 Prim Equiv (PE).  Check the original model to see how many triangles make up each side of the octagon, it should be two, and the total triangle count about 64: two for each side - outside, inside, top and bottom times 8 sides.

What drives up the PE cost of a mesh are mainly:

- Triangle count, especially for the lower Levels of Detail and the physics shape

- Size, if over about 4 meters it gets an increasing penalty because it is seen at higher detail for longer distances on the region.

(if you don't know what levels of detail are - they are simplified versions of the model seen at longer distances.  Textures do that too, a less detailed version is loaded when you are far away and it does not take up much space on your monitor)

[Drongle McMahon]

As Gaia said, it is the physics weight that is high, and you can decreae it as she says.

If you don't specify a physics shape at all, it will be the default convex hull of the whole mesh. That can have many points for meshes wioth curved surfaces and can thus be very expensive.

If you specify a shape, with a special mesh or one of the LOD meshes, and don't "Analyze", you get a triangle-based physics shape whose weight varies surprisingly with the size of the object. It gets larger as the object gets smaller, until any dimension reaches 0.5m (when last tested). At that point the physics shape is switched to the default convex hull, but it can get very high before that happens.

If you "Analyze" the specified physics shape it is turned ("decomposed") into a set of convex hulls, and then the weight does not change with size. It can still be expensive if there are many hulls and/or many points in each. What we need to learen is to minimising the complexity, and thus the weight, of the physics shape while making sure it functions as needed for the type of object you are creating. I don't know a better way than trial and error to learn this.