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On Sun, 23 Jul 1995, James Jones/Nibbles and Bits wrote:

>    Do you think Impact! (you're right, that exclamation point is
> rather annoying) could do a simulation of a Trebuchet?
>
>    [ Aside on what the hell is a Trebuchet:  Ancient siege weapon used
> to hurl rocks, large rocks, corpses and various farm animals (and
> recently pianos and small cars) long distances.
>    Interesting article in July Scientific American about 'em.]
>
>    I'd guess that a simulation would require accounting for friction
> and centrifugal force in addition to mass and gravity.

Impact! would definitely be able to simulate a catapult (that's what I
call them) and could probably do a very good job of destroying whatever
the target is.  Some of the cooler features of Impact! would make this
example very possible...you can assign physical attributes, like mass,
elasticity, roughness...and the program will automatically calculate the
center of gravity.  So, a large, heavy, solid rock object could be flung
through the air and slam into a larger, heavier, more solid wall and
have little or no affect...or it could slam into something with the
attributes of a wooden house and be smashed to bits. (provided, of
course, if you modeled all the seperate little bits)

At this point, Impact! can't simulate wind or general air resistance, but
there may be ways of faking this by putting Gravity wells in key places
or perhaps by by using one of the Force Field engines.  One very cool
feature is the ability to put an envelope on these engines, so that the
strength of the Gravity well would vary over the course of the
simulation....you can also limit the axes that are affected by these
engines, so an enveloped Gravity well or Force Field could be added that
only affects objects on their X or Z axis.


>    It would also be neccessary to simulate a rope. (Perhaps a string
> of short cylinders hinged end-to-end?)

I tried to simulate a chain (individual link objects) with previous
versions, but didn't have much success because Arbitrary Shape collision
detection wasn't implemented yet, but now it should be possible.  I've
got a ton of different things to try out with Impact! now and will keep
you all posted, if the interest is there and you don't mind my
long-winded posts.  =)



>    As a simpler example, can Impact! assign a fixed point of rotation
> to an object, like the board on a see-saw?

Impact! makes use of standard LightWave hierarchies, so all you would
need to is parent the see-saw board to a null-object, or better yet,
parent it to the pivot point for the actual see-saw and it would work.
This is sort of a standard feature at this point...since a see-saw needs
to be perfectly centered on it's pivot point to work properly, it needs
to have the same length of board on each side...Impact! would automatically
calculate it's center of gravity/pivoty point and you'd be in business.



>    I was just thinking that animations of space warfare have been
> overdone... Maybe some medieval warfare would be a nice change. :)

I like the catapult (escuse me, Trebuchet) idea...that one has moved to
the top of the list for Impact! simulations...if it comes out good, I'll
upload the scene to FTP and let you know when/if it's up there.


                                      -David Warner
                                       Event Horizon Graphics


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