In Poser you can use the gravity script for the ingredients in free fall, but you have to do the impact stage manually, deforming frame by frame when the mere details are relevant.

Perhaps Cloth Room might work out for leaves of salad and the piece of cheese (it will require as much effort as doing those manually), but it will splash the burger completely as its considered a dress with no-one in.

Same holds for other software I guess, I'm not aware of any good dynamic burger assembly simulators. Particles systems can do things like that, but these will fall short on the movements of the particles themselves (the salad leaf wobbling etc).

have fun :-)

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though