>> Perhaps what I should do instead is set the derivatives to zero for 
>> the edge points? But that would still give me a set of points that 
>> never actually move... hmm...
> 
> No no, set the 1st derivatives outside of the grid to be zero, then when 
> you calculate the 2nd derivative you could still get a non-zero value.

I might try this if I have time...

> Hehe I just worked out how to use YouTube ;-)
> 
> http://www.youtube.com/watch?v=0GeDiFxCY9s
> (make sure you click the "watch in high quality" text)
> 
> That's using a 256x256 grid, but it's drawing it in 3D as well as 2D so 
> it runs a bit slower (~150fps).

I have no idea how hard this is for your GPU, but my CPU was loaded to 
75% just playing this back!

[I think there's something "wrong" with my PC. Any task involving the 
graphics card seems to put the CPU under an absurd amount of load. Like, 
if I open Notepad and scroll the window, the CPU goes to 100% until it 
stops scrolling. And if I twizzle the mouse wheel, the screen can't keep 
up with me...)

>> That's a GPU?? You'd have to have, like, 50,000,000,000 polygons to 
>> make it anywhere near that smooth!
> 
> Not that many, you just need each polygon to be roughly the size of a 
> pixel.

...which varies according to polygon distance of course. :-P

>> (And the RAM requirements alone preclude doing that.)
> 
> The results are stored as textures on the GPU, the actual polygon data 
> does not ever exist fully, the GPU creates the polys on-the-fly from the 
> texture data.  I think every GPU is fine with a few 1024x1024 textures.

Hmm, well whatever. I'll take implicit surfaces any day! ;-)

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