Kitely Forums

Unless there is a specific reason for the other 2 options ODE is the most trustable classic way

Hi Minethere,

For the time being I recommend sticking with ODE. Bullet isn't quite ready for prime time yet.

I know, I was just trying to be funny...physics don't really matter to me

I happen to be a fan of BulletSim. Well actually, I'm not a fan of any physics engine but I hate BulletSim less than all the others! So I have enabled it on my 3x3 world Panthalassa. Come on by and see if you can feel the difference.

I've hung out on other grids that have converted to BulletSim, and it has worked fairly well. Have you ever had the problem where your avatar hops up and down and bounces down-hill into the water when you were not touching any controls? That never happens with BulletSim. ODE is an old tired project that has NO-ONE working on fixing bugs in it. BulletSim is an active project with very smart people working to improve it. I think it has become much better in the last year and will continue to improve.

BulletSim attempts to be like the SL physics engine, especially where the vehicle script calls are concerned. If you bring a vehicle script from SL it has a chance to run under BulletSim, and that chance will become better as time goes by. ODE never attempted to be compatible and had parameters that were off by 7 times from the SL values for the same call. ODE has known bugs in it that nobody has tried to fix for years. For example, the vehicle linear motor cannot go up! So the only way to make an airplane fly up at an angle is to use the linear motor to go sideways and something else, like buoyancy, to make it go up.

By the way, I spent a great deal of time figuring out ways to move objects in virtual worlds without physics. So all my vehicles and critters will work on any OpenSim grid. I like to say they work DESPITE ODE, BulletSim, PhysX, Havok or any other physics engine.

Minethere Always wrote:I know, I was just trying to be funny...physics don't really matter to me

Yeah, you seem more of a chemistry person.

Deuce Halsey wrote:

Minethere Always wrote:I know, I was just trying to be funny...physics don't really matter to me

Yeah, you seem more of a chemistry person.

lol [I think...lol]

Although it is now six years later... options still continue to hurt my head.

Currently Opensim / Kitely has three primary physics systems: ODE, BULLET, UBODE. The problem is none of the three do all things.

Today we ran into major problems, and had to choose between the lesser of three evils.

ODE is slow, and most vehicles don't run. However regular physics and mesh works fine with ODE. So all our mesh homes and games worked well.

BULLET is faster and a lot of vehicles work under Bullet. Most mesh worked well. However standard physics often broke, rendering many physics-dependent games inoperable. (For example, drop a simple ball down a curving tube with a significantly large opening. The ball will often hang.)

UBODE is fast, but Bullet vehicles don't work well and it is incompatible with many existing meshes, not recognizing mesh openings.

Yes, under Ubode a mesh can be totally re-worked (if one happens to have built the original mesh). Another "fix" is to turn a home totally phantom (or unlink part of it and turn that part phantom)... and use an invisible solid prim to form the floors. Most would agree that's a hassle and not very efficient.

Reality is none of the systems is ideal. I suspect someone is trying to improve these systems regularly, but having three different physics systems on Opensim grids... none of the three ideal... yes, that is a head hurts. ; )

In our case we finally decided to just go back to ODE, because our world has a lot of mesh buildings and games, and we want them to work. Would be nice to have vehicles and a faster system, but one has to choose what needs to work.

Fortunately Kitely allows the world owner to choose between all three, which is good. We at least have that choice. But surely do wish some deep-tech genius would fix one of those physics systems to handle everything correctly. Would be nice to have our games, vehicles and homes all three totally functional.

Tight beanie caps with propellers hurt my head

Wellspring has become an always-on Megaworld (64 regions)... and we've decided to stick with ODE. Why?

ODE is not compatible with Bullet or Ubode, but being the first physics engine, remains very compatible with buildings and standard physics. There are cars and ships that will work on ODE, and ODE-compatible scripts by the score. It may not be the fastest thing on the market, but it works.

Bullet became severely outdated mainly because it didn't recognize cut prims. If the prim is cut or hollowed, we can see the cut or hollow but Bullet recognizes it as solid. Can't walk through open doorways, meshes, etc. In my dwagony opinion, that system should have never even gotten off the ground. Can't help but wonder how it became so widespread with such major problems.

Ubode, same reasons listed above. It's not compatible with either ODE and Bullet, which breaks just about everything. Buildings don't function, Bullet vehicles don't work, can't walk through open doorways, caverns turn solid, etc etc. Ubode is fast and (for some reason) the choice of general preference, but it didn't maintain backward compatibility, which made it useless with countless pre-existing mesh creations and Bullet vehicles.

What is it they say about three strikes?

Summary:
ODE is slower, but works. Cant' use Bullet or Ubode vehicles, but works with everything else.
Bullet has good vehicles, but otherwise bleh.
Ubode is the fastest physics, but is incompatible with everything else. Requires strict mesh rules. Incompatible with many existing mesh creations.

The first strike is not as bad as the third. So Opensim has three physics systems, none of which are ideal. But for us... ODE at least works. It lets us walk through any open door, which is kind of a big deal on virtual worlds.