View Full Version : BULLET - MAKING A CAR DOOR INTERACT WITH the flipping CAR (pun alert)

10-21-2014, 04:37 PM
i've got a question about bullet.

I'm working on my exploding car project again, and i've got a car that sits at a curb and gets blown (flips) to the other side of the street. Someone mentioned to use a proxy object and attach the hi rez car to it after the simulation,
thats brilliant, and works super, making the calculation really fast, and fine tuning a soution in minutes instead of hours.

heres the problem, how do you make all the bits of the car work in bullet? If i say parts, they all fly off!!

so far i've tried parenting a door to the proxy object, but i dont see any settings in bullet to link it to the car proxy object.
it just "ejects" off the car, instead of flinging around. I want it to slam open and closed.

Is there a way to add all sorts of bits and pieces and have them interact with a base parent?

how about a base car flinging (got that animation nicely) and having all sorts of bells planted on the car, how would you get bullet to let the bells interact with the base swaying the bells back and forth as physics allows?

so far i've got the proxy flipping, thats it. I'd like to get the car door to bang around, i havn't found a way for the car door to interact with bullet aside from flying off in the distance, I can manually animate it flopping about thanks to the parent to the proxy concept. That really worked so well, so i'm not stuck per say, i would however like bullet to drive the door animation.

I also want to crumple one side, so i'm thinking morph targets, but i saw someone on youtube do a softbody dynamics desctruction of a car (running into something) that was just amazing. Is softbody the answer, i have not played with softbody in bullet at all.

although interesting, not very realistic as i'd like to see a way for the truck to stay mostly intact and have only dislodged pieces, or major damage in the front end but the back end, well have no damage.
can anyone speaking german tell the fine points of what hes talking about?
he has some great stuff on youtube by the way

heres the car softbody

thanks prometheus - it was lw guru

also whats up with weights(in kg) or density in bullet, i can have a 1 pound object totally flip a 100,000 kg object.. =)

10-21-2014, 05:08 PM
I think the car crash was lightwave guru(german) to bad he hasnīt posted that with english narration.

I also think he just used one single car object that was fractured, donīt know exactly how he did it though.
Car crash is probably quite tricky to do with both crumpling,pieces flying and also have crumple in there..one style at the time is easy, but combining it all isnīt done easy.

10-21-2014, 06:07 PM
i see the second video ; this is not realistic ;in realflow th result much better and real

10-21-2014, 08:32 PM
neither lw gurus impact are directly realistic..the first well it deforms and indents inwards but lack crumpled body..and the second, well ..a true crash crumple and not just break the pieces..it is a deforming metal body, so I am not sure bullet is the ideal tool for it..I may actually think that clothfx will be better for it.
you could also simply morphit and trigger it based on proximity or localized morphing, so you model your crumpled car, you could for instance use textured point map and weighmaps in layout to add that weight textures and then stretch or move it based on weight falloff in modeler to crumple it in a deformed way..splinegod might have some clips on that.

you could also rig the part of the car you want to deform with skelegons and use bone dynamics.


there are multi ways to rig the car with skelegons/bones...in modeler either draw skelegons, or use the parts themself to create skelegons, if you select edges around a car or a part of the car, copy it to another layer it will create polylines..and then you can convert those to skelegons, and then in layout convert to bones.
use Ik booster and dynamic bones so they react to the old dynamic collision objects...not bullet forces.


10-21-2014, 08:35 PM

- - - Updated - - -

aim for this...


10-22-2014, 12:36 AM
here a very nice example created with lightwave



10-22-2014, 10:33 AM
here a very nice example created with lightwave



yes I recall that, good "still" example....I would like to see that in motion though..I reckon it was done with workarounds for a still image shot...but he might have used the cloth fx and hard fx tools in a mix anyway, hardfx for the glass and cloth fx for the body..or maybe that he simply morphed or modeled the deformation manually?

10-22-2014, 11:53 AM
or he use rigid bodies or soft bodies ?
can lightwave create soft bodies ?

10-22-2014, 01:15 PM
ok soft body called deforming body in lightwave

10-22-2014, 04:45 PM
ok soft body called deforming body in lightwave

Setting the terms right, there are two dynamic system in lightwave ..the older one, which has hard fx for hard parts and there is clothfx for softer cloth effects,water look alike effects or rubber effects, but there is also softFx which isnīt as flexible as clothfx,but can be useful for wobbly things or wheels etc. Those are the 3 old dynamics body systems, and apart from that you have the old dynamic wind and collision forces.

Then there is bullet soft body which is more similar to clothfx than the old softFx system.
but we also have these...
and we got bullet parts wich is similar to the old hardfx system.
and we got bullet static
and we got bullet rigid
and we got bullet kinematic

So that is 5 different types in the new bullet system...and apart from that we now also got new forces not to confuse with the old dynamic collision system or wind system..
mostly neither of these system is intended to be working with the older or the newer different parts, in some cases some stuff can work together though.

the old system has value, and can be used with particles and bone dynamics, and particles can create collisions in a clothfx simulation creating wakes etc..in bullet that isnīt possible...Yet.

10-22-2014, 05:13 PM
thanks for informations and explanation
i will learn this systems in lightwave ; i tried them in 3dsmax ; blender ; realflow and they are easy to use and setup and these softwares used the same terms
realflow create very realistic result but can't create good cloth !
i like alot these systems in lightwave after open the example scenes and see some videos

10-30-2014, 03:35 AM
well, here is the example of using a bounding box proxy in bullet with a car parented to the proxy.
solved alot of problems of the parts of the car all flying off.
next up would be to figure out how to make the glass fracture into little pieces.

parenting doesn't seem to be the answer for glass though, seems it needs to be it's own simulation that somehow interacts with the proxy, yet is separate.

note the shadows are also quick proxy objects
heres a quick gif clip =) of the flippin car.