Mesh and Li

[vanettda Lassard]

I have created a rock/stoney hot tube in Blender along with a corresponding PHYS file. I go into second life and open the upload screen. I open the dea file and attach the PHYS file and adjust the LODs. I end up with about 12Li. I upload it into second life and it comes in perfect--12 li. . I then go to features and select prim as physics shape and all of a sudden it jumps to 97? changing the physics shape back to convext hull changes nothing. in a wild grasp I decide to link it to a wooden deck and the combined Li total goes down to 20. but the physic shape need to be defined again. I select prim and it jumps up to 400li? can anybody help me with a deceptively simple solution that I am obviously missing?

[Wulfie Reanimator]

How about a screenshot of your hot tub's physics model? It's a tub -- you probably don't need anything substantially more complex than a 6-sided cube.. maybe an indent if you want to let people freely stand in it.

[vanettda Lassard]

here are the screen shots. I do want the indent. the simplified PHYS could be lower but it fits within my house needs. So you are saying that the PHYS model is causing the issue? I've had more complex PHYS files and never had this problem.

https://gyazo.com/collections/276661b1360c795bd6f7cd5ff54d567a

 

[Wulfie Reanimator]

35 minutes ago, vanettda Lassard said:

here are the screen shots. I do want the indent. the simplified PHYS could be lower but it fits within my house needs. So you are saying that the PHYS model is causing the issue? I've had more complex PHYS files and never had this problem.

https://gyazo.com/collections/276661b1360c795bd6f7cd5ff54d567a

Yeah, you can tell it's the physics shape simply from seeing the LI shoot up after you set the physics mode to Prim. That's when it's using your custom shape, so the change in LI is a direct result of that.

And when it comes to your physic model, it's way too detailed, I would've expected it (and your other physics models) to have high LI before even checking!

When making a physics model, remember that it's never actually seen. It's just there to approximate collisions. For example, you don't need that beveled edge on the step inside the tub. You also don't need that many loops around the cylinder, you can safely remove half of them with no noticable effect on the "shape" of the pool.

Getting rid of those should significantly ease the LI cost of the tub already. There's a whole bunch of other simplifications that could be done, but this might be enough.

Edited October 21, 2023 by Wulfie Reanimator

[Aquila Kytori]

19 hours ago, vanettda Lassard said:

the simplified PHYS could be lower but it fits within my house needs. So you are saying that the PHYS model is causing the issue? I've had more complex PHYS files and never had this problem.

The final Land Impact cost will be the equal to the rounded up value of either the Download cost or the Physics cost, whichever is the highest.

 

If you upload with the Firestorm viewer you can check the Physics costs of your model before bringing it into SL.

At the bottom of the upload window  there is a little Physics cost panel.

• Base Hull  =  the physics cost when the Physics Shape Type is left at the default Convex Hull.
• Mesh  =  the physics cost when the physics model was not Analyzed in the mesh uploader (for Triangle based Physics) and the Physics shape Type is set to Prim.
• Analyzed  =  the physics cost when the physics model was Analyzed in the mesh uploader and the Physics Shape Type set to prim. (Analysing  converts the physics model uploaded in Step 1 of the Physics tab into a collection of convex hulls).

As a general rule, to reduce the Physics cost increase the average size of the triangles in the Physics mesh. This can be done, as Wolfie has already explained by reducing the complexity of the geometry and removing any small thin triangles (quads).

In the example below the physics model was not analysed (has a triangle count of 78). The Download cost = 1.835 and the Physics cost (Mesh) will be 0.5 when rezzed and set to Prim. LI will be 2 when rezzed.

 

Check the download and physics cost when reszzed by clicking on the more info text in the edit floater :

 

Below is an example of  an Analyzed physics mesh. Analysing created a collection of 19 hulls which when the model is rezzed in-world and set to Physics Shape Type Prim would give a physics cost of 7, (6.92 round up). Each of these physics hulls usually costs 0.36,     (19 x 0.36 = 6.84). :

 

 

 

 

Edited October 21, 2023 by Aquila Kytori