View Full Version : Bullet physics tweaks

02-17-2013, 07:33 AM
Hi all,

I have yet to splash out on the latest LW (What can I say? It's the economy right now), but I've tried out version 11's bullet suite.

I've also had some time using Blender (which is a good product for Open Source, and has a number of features above mere 3D production).

What I would like to see incorporated into Bullet is a per-object newtonian physics controller (thrust, torque etc) that can either be driven by set values, or using values attached to a child (or unparented) null in the scene.

Sure, you can keyframe an approximation, which is most likely what many people will do, but (as an example), I would like to animate a craft flying in space (or in an atmosphere), being hit by an object, reacting to that object in a realistic way, and then using realistic physics, compensating for that action according to how you set up the null values at the given frame(s).

I can achieve this in Blender's Game Engine using physics, by using the built in motion controller, and exporting the results as keyframes, but with some of the problems involved with the transition to LW, I would prefer an in-app solution that works a similar way. I've read somewhere about 11.5 having forcefields, vortices and explosion physics, but (from what I've been told) these are all global, and you can't parent them to the object you wish to control (as Lightwave's standard FK ignores the location of the parent object after physics has been applied to the object's coordinates)

So can this be achieved by allowing access to the coordinates of an object that has been affected by Bullet on a given frame, so that parenting another object is possible? And can forcefield/vortex dynamic objects be set to per-object in Bullet as well? I believe this will achieve what I am looking for.

Somewhat related is the ability to have working with compound objects (I'm thinking of a tire on the floor, given torque to make it spin, and being made to move as a result, which is possible at the moment, but to then have that tire's motion be transferred to the parent object, as would be the case for a vehicle). This is something that is currently possible in Blender with their vehicle rigging solution, but it's a kludge, and it doesn't save the results out to keyframes (as far as I'm aware). This one I can probably live without, as I can do the inverse by using wheel rotators on a physics-driven vehicle to give the tires motion, but the thrust and torque I would really like to see implemented if at all possible.

Thanks all.

03-18-2013, 08:58 AM
I really wish this was possible too - I'm currently trying to animate a phone bouncing around on a table top using forces (being bounced by a bass sound wave), and I want to do the simulation using a low-poly proxy, then parent the original object to the proxy.

Seems daft you can't apply the end result as baked position and rotation keyframes, particularly for non-deforming objects. Massively limits its usefulness. Maybe it's possible to link with FXmetalink?

03-18-2013, 09:13 AM
Actually - just been testing and parented objects do seem to inherit motion from bullet-derived movement. Awesome! Didn't even have to use metalink, just standard parenting

03-19-2013, 11:43 AM
Annnnnnnnnnd.... I'm proven wrong. It does seem to translate the position, but rotation is not provided. Very frustrating! trying to get this to work using FX hardlink and DP motion kit, no joy so far though.

03-19-2013, 02:31 PM
There's now a node-based metalink. Use that.

03-19-2013, 02:58 PM
Good to know, but will that support parenting? I got some answers here: