Second Life Forums Archive - Physics on large/heavy builds.

Damien Took

Meat Popsicle

Join date: 3 Dec 2004

Posts: 151

01-19-2006 15:25

Does anyone know how the physics engine evaluates prims and builds to judge their mass?
Is it strictly their size? Is it the size of their bounding box? Does it have anything to do with being hollow or not?

I am trying to build larger people movers, over 10m but under 32 prims, and I cannot get the builds to hover or ground repel.
I would rather not use llSetPos to move them because of the jerky motion in which it moves.

Any input on this would be appreciated.

Thanks you.

Rickard Roentgen

Renaissance Punk

Join date: 4 Apr 2004

Posts: 1,869

01-19-2006 16:21

are you using vehicle code?

_____________________

Zepp Zaftig

Unregistered Abuser

Join date: 20 Mar 2005

Posts: 470

01-19-2006 16:40

The mass is smaller for hollow objects. I'm unsure how it calculates mass, for a box it seems to be approximately volume * 10, but for other shapes I haven't been able to calculate the mass consistently with neither the bounding box volume, nor the volume of the object.

Davan Camus

Registered User

Join date: 13 Sep 2005

Posts: 67

01-19-2006 16:41

...I've found that hovering and MoveToTarget kinds of things start failing as your object's mass gets to about 100. I find it handy to do a SetText with the mass, on a timer, while working on stuff.

If you make your prims very thin, and also hollow them out, you can get big things with low mass. It is a trick though! good luck...

_____________________

Visit Cubes at Alice 100,18.
--------------------------------------------------
Davan Camus, born: 2005 September 8
Out-world location: Santa Cruz, CA
UI Proposal: http://davancamus.hexaflexagon.com/blog/?p=39

Damien Took

Meat Popsicle

Join date: 3 Dec 2004

Posts: 151

01-19-2006 18:03

Sorry, I forgot to mention that I'm not using vehicle code.

I have tried hollowing out the prims but I still get the same results.
It just seems like once you pass a certain size physics are out of the question.

Thanks for the input.

Ziggy Puff

Registered User

Join date: 15 Jul 2005

Posts: 1,143

01-19-2006 18:04

Look up the wiki stuff on 'energy', that'll explain why larger/heavier objects 'run out of steam' and can't hover/float any more after a while. I've been bitten by this too.

And listen to what Rickard says - try turning it into a vehicle and using the vehicle hover calls. That stuff is supposed to keep the object hovering even after it would normally have run out of 'energy'.

Rickard Roentgen

Renaissance Punk

Join date: 4 Apr 2004

Posts: 1,869

01-19-2006 18:10

yep, the vehicle code does not rely on energy and the vehicle hover and movement works pretty much regardless of mass.

_____________________

Damien Took

Meat Popsicle

Join date: 3 Dec 2004

Posts: 151

01-19-2006 18:38

I will look that stuff up, thanks.

Don't you have to have an AV control the prim if it is a vehicle though?
I was trying to design something more automated.

Thanks.

Tip Baker

Registered User

Join date: 12 Nov 2005

Posts: 100

01-20-2006 00:22

Damien,

No, you can make an automated vehicle just fine. And you get one more prim to play with if there is no driver

.

Damien Took

Meat Popsicle

Join date: 3 Dec 2004

Posts: 151

01-20-2006 07:55

Tip,

Sweet! That is the route I will take then.
Thank you all for the responses.

Physics on large/heavy builds.
Damien Took Meat Popsicle Join date: 3 Dec 2004 Posts: 151	01-19-2006 15:25 Does anyone know how the physics engine evaluates prims and builds to judge their mass? Is it strictly their size? Is it the size of their bounding box? Does it have anything to do with being hollow or not? I am trying to build larger people movers, over 10m but under 32 prims, and I cannot get the builds to hover or ground repel. I would rather not use llSetPos to move them because of the jerky motion in which it moves. Any input on this would be appreciated. Thanks you.
Rickard Roentgen Renaissance Punk Join date: 4 Apr 2004 Posts: 1,869	01-19-2006 16:21 are you using vehicle code? _____________________
Zepp Zaftig Unregistered Abuser Join date: 20 Mar 2005 Posts: 470	01-19-2006 16:40 The mass is smaller for hollow objects. I'm unsure how it calculates mass, for a box it seems to be approximately volume * 10, but for other shapes I haven't been able to calculate the mass consistently with neither the bounding box volume, nor the volume of the object.
Davan Camus Registered User Join date: 13 Sep 2005 Posts: 67	01-19-2006 16:41 ...I've found that hovering and MoveToTarget kinds of things start failing as your object's mass gets to about 100. I find it handy to do a SetText with the mass, on a timer, while working on stuff. If you make your prims very thin, and also hollow them out, you can get big things with low mass. It is a trick though! good luck... _____________________ Visit Cubes at Alice 100,18. -------------------------------------------------- Davan Camus, born: 2005 September 8 Out-world location: Santa Cruz, CA UI Proposal: http://davancamus.hexaflexagon.com/blog/?p=39
Damien Took Meat Popsicle Join date: 3 Dec 2004 Posts: 151	01-19-2006 18:03 Sorry, I forgot to mention that I'm not using vehicle code. I have tried hollowing out the prims but I still get the same results. It just seems like once you pass a certain size physics are out of the question. Thanks for the input.
Ziggy Puff Registered User Join date: 15 Jul 2005 Posts: 1,143	01-19-2006 18:04 Look up the wiki stuff on 'energy', that'll explain why larger/heavier objects 'run out of steam' and can't hover/float any more after a while. I've been bitten by this too. And listen to what Rickard says - try turning it into a vehicle and using the vehicle hover calls. That stuff is supposed to keep the object hovering even after it would normally have run out of 'energy'.
Rickard Roentgen Renaissance Punk Join date: 4 Apr 2004 Posts: 1,869	01-19-2006 18:10 yep, the vehicle code does not rely on energy and the vehicle hover and movement works pretty much regardless of mass. _____________________
Damien Took Meat Popsicle Join date: 3 Dec 2004 Posts: 151	01-19-2006 18:38 I will look that stuff up, thanks. Don't you have to have an AV control the prim if it is a vehicle though? I was trying to design something more automated. Thanks.
Tip Baker Registered User Join date: 12 Nov 2005 Posts: 100	01-20-2006 00:22 Damien, No, you can make an automated vehicle just fine. And you get one more prim to play with if there is no driver .
Damien Took Meat Popsicle Join date: 3 Dec 2004 Posts: 151	01-20-2006 07:55 Tip, Sweet! That is the route I will take then. Thank you all for the responses.

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Physics on large/heavy builds.