Real-Time Physics Simulation Forum

I haven't used JBullet before so i'm not 100% sure how it works, you could dig into bullets code to ascertain why the objects are colliding. btCollisionWorld has a function called needsCollision which checks the groups and masks to see if they should collide. I don't know if you can step in there wi...

The way I like to think of the whole collision masking situation is as follows. Think of the group as what ever group the object belongs to and the mask as a list of groups that object can collide with. Internally Bullet just does a bitwise & with the mask and group of either object respectively...

Hello all, So I stumbled across this forum post http://www.bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=17&t=8995#p31234 from a while ago about collision margins and shapes. I watched the video and thought to myself, this is amazing. It's going to solve all of my problems. However when someth...

c6burns wrote:I don't know what code path you've actually changed, but NEON isn't implemented for android. Only for apple.

I'm not using Android devices, i'm using Apple devices.

So I have another question about collision masks and groups. Say I create an object and add it to the world with a given mask and group, how do I then change those? Is it possible to do without removing it and re-adding it back into the world? I read somewhere that this was the safest way to do it b...

Thanks for the reply, CCD isn't an option for me unfortunately. Its too expensive. I don't think my issue is to do with the objects travelling too fast. It could be, but they aren't travelling very fast at all so I suspect its the issue where they are colliding with the back side of the polygons. I'...

I'd like to resurrect this thread because i'm experiencing this issue. It happens with all shapes but it seems that boxes are the worst. Also i'm using a btBvhTriangleMeshShape for my terrain. Is it better to use the Terrain Height field?

c6burns wrote:

Wil McV wrote:SSE seems to work fine on iOS

SSE instructions aren't implemented on ARM processors

Sorry, Meant NEON

Hey thanks for the replies. I have semi solved the issue. It would seem that it no longer happens if I disable SSE by commenting out #define BT_USE_SSE_IN_API around line 83 of btScalar.h I had previously enabled this to try and get a bit more performance but it's not worth it if they is going to ha...

Just another quick update on this issue if anyone is still reading this. I still haven't solved it yet but it would seem that when ever the shape has a rotation applied to its transform that this causes the issue. When I say a rotation I don't necessarily mean that I'm rotating the shape manually. T...

Hey, thanks for the reply. The large box is 10mx10mx10m and the smaller one is 1mx1mx1m so I thought that would be within the scale that bullet supports. I have tried shrinking everything and making it bigger as well and the same thing happens. As for the time step i'm currently calling stepSimulati...

Here is another image that shows a far simpler case. http://i1292.photobucket.com/albums/b567/mcvwi623/physics_issue_2_zpsmjnkt49b.gif The box will collide once but then it seems to no longer collide. Because its only in release builds, it could be an uninitialised variable or something. Does anyone...

Hello everyone, I have a really strange issue that I have been struggling with for 2 days now. Basically when I drop objects on top of other objects instead of them colliding and bouncing off each other like you would expect, they seem to collide, then penetrate each other and shake violently for a ...

Bump,

How have other people done this?

Hi All, I'm currently writing some code to deal with collisions. Ideally I want to know if two objects have just collided, are still colliding or have just separated. What i've currently done is registered for a post step callback so that I can check the state of the overlapping pairs. I iterate ove...