bullet implementation

[com48]

hey guys,

So seeing as I have never programmed in c++ before I set myself a little task to learn it and the hdk... and bullet.

Here is my first implementations of it.

3000 convex objects. using the houdini 11 voronio. Simtime of about 3 frames per second at 10 substeps. nothing to fancy. just dropping and rolling. no glue or constraints.

next big thing to do is implement a first version of constraints. also multi-threading the creation of the objects as that currently slows down the process like crazy on 10.000+ pieces.

greetings,

Lars

[goldleaf]

Well done! And all the more impressive that you've never coded using C++ before!

Out of curiosity, are you doing this in DOPs or SOPs?

[pclaes]

Go Lars and nice to see it coming together! Really good sim times with your sop implementation. And here's me hoping this is going to be one of many hdk projects, now that you have tasted some of that speed, will you go back to python ?

Would love to take a look at your code some time and integrate it in a scene with my delayed load instancer . Rendering a huge amount of super high detailed debris.

Good luck with it and I'll be keeping an eye on your progress here as well.

[realer]

wow! awesome work and actually the first thing i see coming of bullet that looks stable and seems to come to a rest very nicely! great work and sick simtimes

[Macha]

Wow that's nice! I wish I had any clue about how to do such things. Very lovely indeed.

[com48]

thanks guys,

@goldleaf: yes it's Sop based. it's actually very stable for convex objects, ones you need concave you will get some speed slowdown. nothing to major though. basicly the difference between 1 frame per second or 5 frames. ofcource on 10.000 objects that might be a very different story.

@peter: haha I still love python. but for stuff like this I don't think I can go back. maybe the inline cpp sop can save me some day

@realer: there nothing to special about this sim. just turn down the bounce and up the friction. makes look a hole lot less cg.

With a little luck I might be able to release some of the code maybe one day.(fingers crossed)

[ikarus]

fantastic! implementation like that could have a lot of practical use.

if you manage to get constraints working that would be some ICE-type stuff I bet

[com48]

10.000 objects without constraints, I have implemented constraints and also being able to break them.

hopefully I can post a good video of that soon.

[CeeGee]

Great work... nice amount of object, speed?

[com48]

is averaged at around 4 and a half seconds a frame. about 10 min for 150 frames.

[goldleaf]

That's awesome lars! Is the constraint system have a threshold for breaking, or are they simply there, or not there?

[com48]

there based on a max impulse threshold. if the force is greater then the threshold they will be removed from the scene. as I'm creating them with points it nice to use a vopsop and some noise to create weak pockets of constraints to drive the simulation.

[com48]

also added a max distance of separation between the objects. the implementation of bullets getAppliedImpulse gives a good value to determine if the constraint is under a lot of stress but means the bodies can be far apart and not under a lot of pressure.

[blackchicken]

very very nice, hih, looks like that bullet is more and more wisible in houdini thats a good note. One of implementation of my friend from Czech rep.

[com48]

very very nice, hih, looks like that bullet is more and more wisible in houdini thats a good note. One of implementation of my friend from Czech rep.

Hey blackchicken, yea i've been following that thread closely. it looks great but I think there is a small difference in the philosophy of the approach. sadly I haven't seen a linux build yet so I haven't been able to test his version but it looks great. lots of nice features!