I’m creating a simulator that uses “Force” in Motion actuators to slide my object along a plane surface. I’ve been using Sumo physics up to this point but would really like to use Bullet physics instead. The problem is that it seems that no matter what I set Friction, Damping, Mass or Force to, my objects don’t want to slide, only roll.
I’ve tried some of the “work-arounds” I found in past threads, but it’s not working. Am I missing something or is this just a big bug in Bullet physics?
Thanks!
I’m quite sure it’s a bug. For example I’ve tried using linV to ram a cube into a tower of cubes. Not only does the sensor decide to pulse (it’s “Always” but not pulsed), but gravity has no effect on the moving object.
I’ve been able to get objects to slide in a new scene created following this thread:
https://blenderartists.org/forum/viewtopic.php?t=61254&highlight=slide+bullet+physics
But am unable to get it to work with my prototype simulator no matter what settings I use for friction, mass, etc.
FYI, there is also an ongoing thread on this topic at Erwin’s site:
http://continuousphysics.com/Bullet/phpBB2/viewtopic.php?p=718#718
I hope he is able to fix this bug. Sumo physics will be sufficient for my current project, but lacks the realism possible with Bullet physics.
I have already reported most of the bugs you have found with your projects (except the workaround not possible in existing projects)
The .blend file I sent to Erwin shows 3 bugs
1). Friction is higher on the y-axis then the x-axis
2). LinV objects don’t really fall down.
3). Objects running into a wall using dLoc squeezes through it.
EDIT: I found the workaround works with existing projects according to doing it in one of my old game engine files, but indeed the object does slide better in sumo as the slope of friction isn’t so steep.
Hi Icoxo,
I saw your posts here and the Physics Sim Forum.
How did you get Bullet Physics to work with an existing project?
I just switched to bullet and did the workaround I mentioned on the forum. Though the friction has to be pretty low to get it to work (like 0.010(could be up to 0.050 for steep surfaces)).
Another problem I have is that if you have an object with multiple actions:
left, right, forward, and backward for example, you can only do one at a time. So no diagonals! I think this was with LinV, not force.
Icoxo: I’ve followed your “workaround” and it doesn’t work for me. No matter what settings I change mass or friction, my objects won’t slide. Any other ideas?
Post it at Erwin’s site.
bigkahuna, strange, I managed to do the workaround in two of my other game engine files and they worked, just remember that the friction on the y-axis is a bit more then on the x-axis for some reason.
bigkahuna, strange, I managed to do the workaround in two of my other game engine files and they worked, just remember that the friction on the y-axis is a bit more then on the x-axis for some reason.
Yeah, it is strange. I’ve tried setting friction to 0, 0.01, 0.05 and everything in-between. I’ve tried hardbodies on and off. I tried creating a different ground plane. I’ve tried every mass value from 0 to 10,000 (max). It just won’t slide.
I’m thinking it’s because of my “object’s” mesh. It’s a low-poly ship model with a flat bottom. Sumo sees it like any other “box” type object, but Bullet doesn’t seem to.
Although it’s still a prototype, the project is already pretty involved (a fair bit of Python code and logic blocks), so I’m not sure where the glitch is. I’m going to make another version before working on the final app, so I’ll give bullet one more try then.
Sorry for “beating around the bushes” I couldn’t help noticing that someone mentioned that linV overrid gravity and other stuff… isn’t that the idea of linV? Or else it would just behave like Force…
going back on topic, I was disencouraged with the “rolling objects” phenomenom too, but I’ll give it another try now with the friction settings, thanks! (i don’t think of this as a bug actually)
No. LinV is used for an object to reach a speed instantly. Essentially, it’s going into the object’s status and setting its speed to a value. Force is for gradual, “realistic” speed changes.
oh, well, thanks for clearing that out 
silly silly me…