Sunday, May 14, 2006

Goo Fragmentation

In recent days I have modified the operation of the cannon of my Gun Balloon, to add effects that I find rather pleasing: there is now a two-stage particle effect upon impact, consisting of a brief yellow/red explosion and a longer-lasting plume of smoke, and more importantly, the shell itself produces shrapnel. A quick sensor call is used to determine whether there are avatars within three metres of the detonation point, and, if so, the shell launches a fragment directly at them at 20m/s (plus their detected velocity - there will be no escaping here!) If not, or if there are less than three avatars in the radius (likely) up to three fragments are ejected in random directions, biased towards the horizontal.

Thus, for instance, if nobody is around the point of detonation, three fragments will shoot out at random. If one person is within three metres, one will shoot at them, and two others in random directions. And so on. It would be nice not to have to rely on this sort of targetted fragmentation, but in practice one cannot easily simulate a blast wave and dozens if not hundreds of potentially lethal fragments exploding in all directions - thus three will have to serve.

Now, the scripting element here was influenced by the thread in the forums regarding a Grey Goo Fence. This construction has been put into place to counter the threat of self-replicating objects which threaten the integrity of the Grid, which I'm sure we would all agree is a laudable aim. In theory, any device rezzing objects at a rate of more than 40 per second - or rezzing objects which rez other objects and so on down the line - will find itself shut down for a period.

As a figure this does not seem too unreasonable, and given the rezzing procedure of each shot of the cannon:
  • one cannon shell
  • three fragments upon impact of shell
  • one empty cartridge
totalling five rezzes per shot, I decided on a rate of five rounds per second, meaning twenty-five rezzes, to be absolutely safe.

I have to say though that this has not turned out to be the case. The rate of fire is controlled by a timer in the cannon, which issues linked messages to subscripts whenever it fires whilst the trigger is being held. Thus it is possible to control the rate quite effectively. For any timer interval below 0.25 seconds - in other words, any rate of fire greater than 4 per second, or any rate of rezzing greater than 20 per second - one receives after a few seconds of sustained fire the ominous message:
grey goo fence: rapid or recursive rez
This is not as was advertised. I was concerned that the original version of the fence would hamper the operation of such creations as fractal trees, but really, if we are to have a fence at all, let it be set high. If I had not deliberately tested this I would be facing complaints from purchasers, I'm sure - even if one must fire for several seconds before encountering this message.


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