Havoc Physics

[Quinavery]

Hello, this is nothing new, but I have noticed some things about the Physics Engine...

Can someone explain to me what is going on here with the Prim Attributes?

Thank you : )

 

 

[Lindal Kidd]

I'm no expert at the Havok physics engine. But I do know that prims touching each other, made Physical, experience a small repulsive force. This is what makes the annual "Cake Stage demolition" at the SL Birthday event so spectacular. The clever doggie here seems to be taking advantage of this effect to get prims to spin and swing with "perpetual motion".

[Ardy Lay]

@Falcon Linden

@Simon Linden

Y'all might find this entertaining to explain.

I will make some guesses.

The physics engine does not do lighting for Second Life.

I want to say that physical representations in Second Life are imprecise numerically out of necessity because more precision requires expensive computational resources.

Physical shapes and sizes are not identical to visible shapes and sizes.

Energy is added to the physics computations to keep objects from sticking to each other in disappointing and computationally expensive ways.  Touching objects result in longer collision solution times.

Interpenetration resolution is a process where physical representations found to be occupying each other's volumes are pushed apart from each other using velocity injected at varying vectors until their physical volumes no longer intersect.

Physics is calculated 45 times per second and is only allocated a portion of that 45th of a second to complete.  Solutions that are taking too long to resolve are short-cut with an estimate using the results of the previous iteration.  Failing this, the contributing objects are frozen for a period of time, then released in increments to prevent physics loads from hobbling the rest of the simulator.

Edited June 22, 2022 by Ardy Lay

[Love Zhaoying]

28 minutes ago, Lindal Kidd said:

The clever doggie here seems to be taking advantage of this effect to get prims to spin and swing with "perpetual motion".

Clever indeed! My doggies can barely speak, and only understand a few dozen words.

I need to get one of those floor mats with all the word buttons.

Maybe then, they will be able to grow opposable thumbs to learn Second Life and demonstrate Havoc Physics.

[Ardy Lay]

3 minutes ago, Love Zhaoying said:

Clever indeed! My doggies can barely speak, and only understand a few dozen words.

I need to get one of those floor mats with all the word buttons.

Maybe then, they will be able to grow opposable thumbs to learn Second Life and demonstrate Havoc Physics.

Yes, I want to see them keep going at this and show us how physics behaves in Second Life.  I just fear that they will lose interest after finding that physics in Second Life is not a precise and accurate model of real world physics.

[Ardy Lay]

I must try to make a bridge like that!

[Love Zhaoying]

Unfortunately, the answer to the original question may be along the lines of, "Nobody knows exactly because Havoc is a third-party engine. There are not necessarily 'real life' counterparts to the things you can do in Havoc".  Etcetera.

[Ardy Lay]

Just now, Love Zhaoying said:

Unfortunately, the answer to the original question may be along the lines of, "Nobody knows exactly because Havoc is a third-party engine. There are not necessarily 'real life' counterparts to the things you can do in Havoc".  Etcetera.

But, they are using the scientific method!  They can figure it out and explain it to us!

And yes, don't expect this wacky numerical hooliganism that is "Havoc" and the real world to work alike.

[Bree Giffen]

Those look fun to try building. Whenever I set things to physical they somehow manage to roll off into the distance. 

[Rolig Loon]

8 minutes ago, Ardy Lay said:

I must try to make a bridge like that!

I was thinking the same.  I want to fiddle with some of the other devices as well, like that lovely trebuchet.  As a scripter, I tend to approach movement challenges with LSL tools, but there are certainly places where you can get more realistic effects (and potentially easier) by messing with physics.  Like a lot of people, I've experimented with exploding structures, hamster balls, and anti-grav toys, but not in any systematic or scientific way.

[Love Zhaoying]

15 minutes ago, Ardy Lay said:

But, they are using the scientific method!  They can figure it out and explain it to us!

Brilliant!

[Love Zhaoying]

Side note: Unless the original poster created the scripts themselves and is aware of what they do.. things can get scripted to "change" the physics behavior in reaction to timer, touch, collision, etc.  That's an example where the "real world" physics can't be diddled the same.

[Lucia Nightfire]

Havok isn't to blame.

LL nerfed the physics engine many times in preparation for pathfinding, particularly with energy transfer.

Edited June 22, 2022 by Lucia Nightfire

[Ceka Cianci]

I'm not anywhere near experienced in these things and don't even know the first thing about the engine..

I can say it was really interesting to watch and was amazed it does all this without scripts..

To me, it looks like the same energy that is pushing them apart from the outer shell is the same energy  on the inner shell pushing inward and outward which is really the neatest thing..

It makes me want to go play with it now!! \o/

I love how he created a spin with a ,tetra cut I think it's called, and a cylinder.. I wonder if steam punk creators use this..

I'm gonna be playing with this today for sure, just to see what I can come up with..

Edited June 22, 2022 by Ceka Cianci

[ValKalAstra]

2 hours ago, Ardy Lay said:

Interpenetration resolution is a process where physical representations found to be occupying each other's volumes are pushed apart from each other using velocity injected at varying vectors until their physical volumes no longer intersect.

That would more or less be my guess. Anyone that has ever played a game with the Havok engine can attest to the abrupt chaos when two physics objects intersect. The two objects will push away from one another, usually with wild and explosive results.

This can lead to some funky and funny bugs where players circumvent entire levels by slamming a kitchen board into the floor in ways that result in an aimed physics tantrum.

Also for those sculptures, if players without engine access can aim the collisions well enough to make use of it for glitches, fun and chears, people with access to the physics properties like in SL can probably create controlled experiments with it.

[ST33LDI9ITAL]

Well, first of all I love your physics lab and builds! Looks like a lot of fun! Intro vid is hilarious, lol.. I like to play with physics as well and would def like to join you sometime. As well as get ahold of whatever you smoking! To answer though... there is no RL correlation with Havok physics and unseen forces in reality. At all. It's just software glitchy jankyness at it's finest.

 LL's implementation of Havok isn't very good. It's outdated (like everything else) and they don't use nearly all the features that Havok provides. SL really only provides a rather small chunk of Havok.. the basics I suppose. If you'd like to see a good implementation in a sandbox environment then I would HIGHLY recommend you to go pick up Garry's Mod (it's a physics sandbox game, based on Source physics, which is based on Havok) and give it a whirl. Or, you could pick up Unity engine and play around in it, as it supports a Havok implementation as well, along with their own physics and 3rd party. A lot of physics bugs in SL, yes they are bugs and not features, are due to the constant counter energy, repulsion that is applied to physical objects, rounding errors, a physical object's "energy", and things others have mentioned already. 

Overall, it's just a half done implementation. Garry's Mod is just as old as SL and had way better physics simulation. Constraints, joints, soft body, and done in a way that was much more accessible and easier to use for the user. If SL had the same feature set as Garry's Mod, it would be incredible. But no, such will never be. LL doesn't have the resources, expertise, or will to do it. They will forever be smashing bugs on the broken engine and viewer they refuse to rewrite until the end.

I've built and seen some amazing contraptions on GM... talking massive all physical robots, cars with actual suspension and even gearboxes or transmissions made of actual gears. Tornado simulations. All kinds of contraptions people have made over the years. Sure, GM has it's fair share of bugs as well, as most physics engines and simulators do, but I still encourage you to at least try it out so you can see how Havok's potential on here is nothing near what it could be. There is a successor to GM in the works called S&Box that's been in making for awhile now and due to be released maybe later this year or next. So looking forward to that because it will be awesome! 

Also, if you want better physics, use mesh instead of prims. Cause prims are kind of wonky and retarded in some aspects. Take the sphere for example. It will stop rolling on a flat surfaces and just kind of skids. But, if you make an icosphere.. it will remain rolling. It's just a shame we are limited to 256 hulls/faces. Because we could have a whole nother resolution of icospheres if they'd bump that up to 320, giving much better sphere physics.

Edited June 28, 2022 by ST33LDI9ITAL

[Vincent Nacon]

On 6/22/2022 at 2:16 PM, Lucia Nightfire said:

Havok isn't to blame.

LL nerfed the physics engine many times in preparation for pathfinding, particularly with energy transfer.

Andrew Linden is the one to blame for the countless physic glitches, which most still carried over to latest Havok 4 update and the pathfinding update. I'm glad he's gone from the lab. However, they (Simon and Falcon) didn't nerf anything other than the impulse force and speed limit. Energy transfer is still intact. Even they don't fully understood what Andrew had done, which is why we're still dealing with all the terrible patched up fixes today.

[Lucia Nightfire]

1 hour ago, Vincent Nacon said:

Andrew Linden is the one to blame for the countless physic glitches, which most still carried over to latest Havok 4 update and the pathfinding update. I'm glad he's gone from the lab. However, they (Simon and Falcon) didn't nerf anything other than the impulse force and speed limit. Energy transfer is still intact. Even they don't fully understood what Andrew had done, which is why we're still dealing with all the terrible patched up fixes today.

Andrew returned in November. He is now known as Leviathan Linden. Maybe ask him to fix his bugs?

[Mollymews]

5 minutes ago, Vincent Nacon said:

Andrew Linden is the one to blame for ...

Second Life

without Andrew Linden there wouldn't be a Second Life

Philip Linden at the SLB19 mentioned that in the early days of Second Life, Linden was scoffed at by 'the industry' for being a bunch of hackers who didn't know nothing.  And Philip said yes we didn't know anything about how to build a 3D virtual world that emulates the real world  from a design perspective and neither did anyone else. So we (;Linden) went with design-by-doing. Which means in practice, we hacked it together, to get it up and running and making money before the VC funding ran out. We meaning Cory and Andrew, hackitty hack hack. Wooo! that works, not great but oh! well. Crude actually working is better than elegant not working at all. So release it and we come back and have another go at it another day

which is what Linden did. 19 years later, Second Life still up and running, and being unhacked (Improvements Viewer most recent part of the work) and Second Life still making money

Oz Linden let it slip on occasion that the codebase he inherited as VP Engineering drove him and his team nuts sometimes, when responding to user requests. But when he stepped back and looked at the Second Life codebase in its wholeness, then was a marvelous thing. And that every software engineer knows that hindsight programming is even more marvelous

[Vincent Nacon]

8 minutes ago, Lucia Nightfire said:

Andrew returned in November. He is now known as Leviathan Linden. Maybe ask him to fix his bugs?

Oh you got to be kidding me... 🤦‍‍

Edited June 29, 2022 by Vincent Nacon

[Mollymews]

3 minutes ago, Vincent Nacon said:

Oh you got to be kidding me... 🤦‍‍

so how is your virtual world product getting on ?

[Vincent Nacon]

8 minutes ago, Mollymews said:

so how is your virtual world product getting on ?

Oh they're great! Thanks for asking. They ended up being part of my large collection of personal backburner projects, gathering dusts in the hot attic, with a bunch of webs and skeleton of mice.

 

 

Yeah... I should probably do something about them.

[Love Zhaoying]

36 minutes ago, Mollymews said:

But when he stepped back and looked at the Second Life codebase in its wholeness, then was a marvelous thing. And that every software engineer knows that hindsight programming is even more marvelous

 

[Mollymews]

On 6/23/2022 at 2:09 AM, Quinavery said:

Can someone explain to me what is going on here with the Prim Attributes?

 

my only explanation is as has been mentioned in the vid already, which Ardy touches on also.  The repel force when two prims collide can be greater than the prim's mass and gravity. Gravity in Second Life is not constant, is prim (and/or script) dependent. So two other-wise identical prims can be made to fall down at different rates of speed

with what you are showing here tho, I now want physical avatar attachments. I be able to make hair and neko tail that wouldn't intersect my avatar body. I probably end up being a worse physics lag monster than a sion chicken but would look pretty cool

[Love Zhaoying]

10 minutes ago, Mollymews said:

with what you are showing here tho, I now want physical avatar attachments. I be able to make hair and neko tail that wouldn't intersect my avatar body. I probably end up being a worse physics lag monster than a sion chicken but would look pretty cool

Would this act kind of like flexi-hair?