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Having trouble with physics

Posted: Fri Apr 24, 2020 8:44 pm
by Joe Love
I'm having a strange physics issue with my builds. Here's a test I did ... On the Kitely Merchant sandbox, I built a simple prim cylinder, 10 x 10, then opened a hole in it. Nothing fancy.. I stand on the cylinder and I fall through the hole. Works as expected. I take a copy of the build to my region, Evermore, rezz it. I stand on the cylinder and i do NOT fall through it. I delete it and rebuild it from scratch, and still I do not fall through it. Any ideas? Thanks Joe

Re: Having trouble with physics

Posted: Fri Apr 24, 2020 9:07 pm
by Ilan Tochner
Hi Joe,

This is happening because the sandbox is using a different physics engine than the one you've selected for your world. The Kitely Merchants Sandbox is using UbODE and your world is using BulletSim. BulletSim has issues with handling hollow prims, while ODE and UbODE don't have that issue.

If you wish to use hollow prims then I recommend you go to the Advanced tab of your world's Manage World dialog and change your world's physics engine to UbODE or ODE.

Re: Having trouble with physics

Posted: Fri Apr 24, 2020 10:55 pm
by TheMad Tadder
OK, in all honesty and with no intention of creating any sort of negativity or backlash, I would just like to point out MY EXPERIENCE since the upgrade to 9.0 and the ODE and UbODE platforms.

I can't actually say that ODE and UbODE are handling physX better than Bullet platform. And I have good reason with extensive experience.

In Kitely, I made a prim Lighthouse which the tower was constructed with several layers of cylinders, hollowed and tapered slightly. I took the prims to blender and converted them mesh. I know this method is controversial, but I have had years of success in OpenSim 8.0 and in SL using this method. I am an accomplished builder with over a decade of building experience and blender program abilities.

I then uploaded my new lighthouse objects inworld and onto a Bullet platform region and I was successfully able to walk up the spiral stairs completely to the top and out a door and all along a prim to mesh hollowed cylinder viewing platform with also a prim to mesh railing-- even without walking out or over it, as happens in many cases with prim to mesh railings. I must say I was complimented by many who saw and used it and I was indeed very happy with my accomplishment. I had no problems moving around it at all and I ventured on with texturing my achievement.

Then, while still in the final stages of finishing my Lighthouse, the region I am on was changed to UbODE with the 9.0 rollout and after that day I discovered I was no longer able to the traverse the tower stairs-- ascending or descending-- and when I walked on my viewing platform-- which performed as it was built (prim to mesh) on a Bullet sim-- my feet then sunk into it and I was unable to freely move around the tower completely (as though I was blocked) when just the day before I had been able to move throughout the entire prim to mesh structure when the region was operating on Bullet physX.

Believe me, I was entirely perplexed and then gutted because I was so close to finishing my Lighthouse project which had taken me over 4 months to build. So, my original prim build, which I converted to mesh worked perfectly on a Bullet PhysX region is now no longer 'workable' and I must either rebuild the entire structure in prims (or some other method) or trash the whole thing. I'm still undecided on that project.

Anyway, another sad draw back I've discovered with the new 9.0 ODE/UbODE platform is that 1000's of vehicle scripts (boats, cars & planes) are now rendered useless because the coding for all of them (and many are beautiful 'collectors items') was Bullet PhysX and there are very few new vehicle scripts with ODE or UbODE coding. Therefore, most of my inventory of beloved vehicles are now useless as well on ODE/UbODE operating regions.

I do believe in moving forward; when so many fought it, I welcomed mesh and learned as much as I could about it to begin creating with it after years of building with prims and sculpts. It is the 21st century after all, yet I'm of the old fashioned thinking; "If it's not broken, why fix it?" especially now when it comes to razzle dazzle upgrades.

Truly, without intention of insulting anyone or thing, I'm simply stating I've mostly encountered drawbacks with the 9.0 OpenSim upgrade and the ODE or UbODE PhysX applications. Nothing more appears to me as being improved, in fact, quite the contrary with my Lighthouse experience and, therefore I can not give a single hurrah to the 9.0 upgrade.

Well, perhaps server side is less taxed and maybe that's a good thing for less lag-- even though I rarely experienced lag in Kitely anyway-- but current inworld experience and performance with the things I've enjoyed for years has sadly degraded.

OK, that's just me. I'm sure plenty of folks are loving the upgrade. But, if there are folks that are having the same issues as I've encountered, feel free to comment with your agreements here. Perhaps it should be known, purely for decisions of grid improvement, that there is more than one person that's not really impressed with the 9.0 upgrade.

I still love Kitely grid and where I can I'll use my antiquated objects and create with my 'old ways' of building.

Thank you for reading down this far if you have and I wish everyone a wonderful time inworld.

Stay happy, safe and well in these days.

ONE FINAL NOTE: I have just been informed by Ilan Tochner, thank you sir, that BulletSim PhysX is still available as a choice to use on a region YOU own. So, I will soon be purchasing a mega region and running it on BulletSim this May. For this I shall raise a BIG HURRAH!

Re: Having trouble with physics

Posted: Fri Apr 24, 2020 11:23 pm
by Joe Love
GREAT suggestions.
Ok. I left for a few hours and came back to check the physics.. everything is working fine no physics issues. I can fall through the holes. IDK. I made no changes. Maybe the rolls at work. :D
All of my houses are mesh... so I can adjust the physic with the uploads. I try not to use prims, except for testing.

Evermore has lots of drivable roads, and we love racing. But I had to change to BulletSim a year ago to enjoy the driving. Have had little issues, but nothing I couldn't fix. LOVE the speed and upload in Kitely!!!

I may test ubODe and ODE physic engine to see if it make a difference. THANKS Joe

Re: Having trouble with physics

Posted: Fri Apr 24, 2020 11:24 pm
by Ilan Tochner
Hi TheMad Tradder,

The issue you encountered with your mesh is due to how ObODE treats meshes that weren't uploaded with a collision mesh (a physics mesh). Whereas ODE uses the mesh itself as the collision mesh when no collision mesh is provided, UbODE treats the object as being Convex when the collision mesh is missing.

The reason we switched the Kitely Merchants Sandbox to use ObODE is because many people upload and test content in that region and we wanted them to encounter this issue immediately, and not after one of their customers has taken their mesh into a region running UbODE.

To avoid this problem and ensure that your mesh will work as intended on all physics engines on all grids, use the following upload procedure: viewtopic.php?t=3199