here the requirements are not the same as in games.
For these areas, there still aren't many alternatives to Bullet, ODE, Havok, Newton and Ageia. The one and only alternative is Vortex from CMLabs which is superior to all the other in e.g. precision of constraints, friction model etc. but it doesn't scale well at all, and the direct solver is not great at handling ill-conditioned problems that often occur in interactive simulations. OpenTissue is also an alternative, but very slow if you go for precision and in addition you need to be very keen on templates to use it.
My interest in validating physics engines by measuring residuals, unphysical damping, computational complexity, realism of friction model, etc. is based on exntensive experience from real-world examples (e.g. medical sims, vehicle sims, robotics) and insight into various classes of algorithms.
I most certainly think such tests can be of interest to game developers, and certainly to engine developers.
The reason I don't like "plausibility" is that it is very far from well defined. It never helps anyone to understand how to further improve a physics engine or the algorithms used - and STILL the details of such algorithms is exactly what is discussed in these fora all the time - but usually with no metrics whatsoever. You can say that something is plausible, but I have never heard anyone say that this is very plausible or not plausible enought - so the metric is useless when improving engines.
You say "plausibility, robustness and speed". Well - why not determine what these are in terms of what can be measured?
Speed is typically about measuring computational complexity and overhead of heterogeneous systems when growing from small size to large size. It is also about benchmarking standardized simulations with some constraints on precision.
Robustness (e.g. absence of blow-ups and jitter) is usually very closely coupled to e.g. energy/momentum conservation, dissipation and timestep - and therefore also couples to physical correctness. For example, a symplectic or variational integrator typically makes your simulation dramatically more stable than first order explicit Euler - and the reason is that it gives much smaller (bound) global errors in the physical conservation laws. Even Disney benefits from this...
Don't want "real physics" but "animation physics". Yes, but the point is
that this is still well defined, or at least it can be!
I say: It makes very much sense to understand animation physics in terms of physics, but I would never dream of asking a Disney animator to use "more realistic physics".
Plausibility is in the eye of the beholder and some try to define it in terms of psycho physics but more than anything it means very different things to different people and in different contexts. It is usually used as an excuse, and therefore I don't use it much...
Dirk Gregorius wrote:I don't get this point. AGEIA, Havoc and also Bullet main purpose is physical simulation in games. You will sell no more licenses of your engine if it is more physical correct than another. The most important things that count are plausibilty, robustness, speed, and ease of use. If it is then physical correct this is nice if not it really doesn't matter.for stress testing physics libraries beyond "plausibility" (still hate that term) of blow-em-up and debris.
I suggest reading: M. Blum: Using Dynamics in Disney?s Production Environment
A quote from the slides:
"Don't want "real" physics but "animation" physics."
You can find it in the Baraff rigid body Siggraph presentation from 1997.
I agree that well defined testbeds are a nice thing to have, but physical correctness is not the major criterium. This totally misses the point.