In article <39627b45@news.povray.org>, "Rune" <run### [at] inamecom> 
wrote:

> I'm getting closer to an understanding of your particle system, but 
> there's still some things I don't understand. I appreciate that you 
> have so far taken the time to discuss it with me.

No problem. :-)


> So when using method 2 (and method 0, for that matter) the total 
> number of cycles for the entire animation (for example from clock=0 
> to clock=1) is always exactly the same, independent on the number of 
> frames?
> 
> Then how is the number of cycles chosen?

Something like:
particle_system {
    iterations TOTAL_AMT*clock
    time TOTAL_TIME*clock
...
for method 0,

run_particle_system {PART_SYS_IDENTIFIER
    iterations NUM_PER_FRAME
    time TIME_PER_FRAME
...
for method 1, and

run_particle_system {PART_SYS_IDENTIFIER
    iterations TOTAL_NUM*clock_delta
    time TOTAL_TIME*clock_delta
...
for method 2.


> Yes, that's the advantage, but you still haven't told me what the
> DIS-advantage is, using method 2.
> 
> Which advantages has method 0 over method 2?

None, other than simplicity of coding.


> Which advantages has method 1 over method 2?

If you want to set up a certain amount of time between frames and render 
a longer animation to see the system progress, you would probably choose 
method 1. Having the particle_system time tied to the frame number is 
it's only disadvantage, and it is only a disadvantage in certain 
situations(the majority of situations, given POV's usual animation 
techniques, but not all).


> I can understand that.
> 
> What do I do If want to if I want to render frame 60 to 70 out of 100 
> in an animation where the particle system is synchronized with the 
> clock using method 2?

You will have to have frame 60 calculate the whole particle system up to 
that point, then you can continue from there. It shouldn't be difficult 
to set up the scene file to do this automatically.

BTW, persistent variables seem to be broken in my compile, :-(, I think 
it might be something to do with the official Mac version's interface 
(since I haven't modified any of the persistence code), so I can't even 
test this feature in an animation(I have to do it all within one frame, 
and "pretend" it is an animation).
But I might have come up with an even better solution: file input-output 
of the particle system, like the feature for radiosity info and photon 
mapping. save_file would save all particle system data to a file, and 
load_file would replace the current system with the loaded data. You 
could do the calculations for a still image once and tweak rendering as 
much as you want.

-- 
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/

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