[Bf-funboard] Particles

Paul Lunneberg bf-funboard@blender.org
Fri, 15 Aug 2003 11:51:15 -0400

An idea I had from the Lightwave 8 demos I watched online during siggraph that
could be applied to the rewrite of the particle system.

Newtek showed a new feature of some new particle system effect that once the
particles have been calculated you would then be able to grab a specific
particle and move its motion path or even just its location during that key
frame and it would modify the path without haveing to recalculate all the
particles again.  This is a huge time saver especially when your trying to get
particles to avoid the camera correctly or if something looks great except one
small piece.

They also showed this feature and how it applies to cloth dynamics and such that
if a characters dress is waving around and the characters leg pops through the
dress on one frame you can just pull and modify the verts on that frame instead
of trying to recalculate or using higher res deflectors.

Something to think about for possible use in the new particle system rewrite and
even in any other type of simulation work being done.  Water, cloth, hair..

Who knows.  Just a thought.
Paul Lunneberg

Quoting Martin Poirier <theeth@yahoo.com>:

> > >> There's also the important topic of memory
> > >> consumption, and having a
> > >> system that can be evaluation at any timeframe
> > (as
> > >> opposed to needing
> > >> to do it in forward timesteps). The choice for
> > >> keypositions in Blender
> > >> particles is based on that.
> > >
> > > I think the best way to do that while still using
> > > little memory would be the variable time interval
> > > keyframe thing that I was explaining earlier.
> > 
> > I don't find that info at our mailing list, if you
> > mean at the forums,  
> > can you provide a link to that?
> Oh, I thought I had explained this earlier. Anyway,
> the concept is simple: instead of keyframing at a
> fixed interval, you only keyframe when it is necessary
> to do it (basicly, it would work on the same kind of
> algorithm that removes superfluous CVs from NURBS
> curves).
> Those keyframe would contain this kind of data:
> - Time
> - Position
> - From and Away vector (their length are not fixed,
> they help in the interpolation both of the position
> and of the time, just like bezier handles).
> Advantages: 
> - saves memory
> - faster load/save of big particles system
> - the ability to define keyframe at non-whole time
> (fram 10.5 for example) when extraordinary event
> (collisions) happens that disturb the smooth motion of
> the particle.
> - Contrary to fixed keyframes, the motion between two
> keyframes is always a curve, you don't have to mix
> data between keyframes to create smooth motion in
> between keyframes.
> Disadvantge
> - Slower to recalculate (could be optimized probably)
> - a little slower to calculate the motion of the
> particles. Since the keyframes are not fixed, you have
> to iterate through the list until you find those you
> need to use.
> that's about it, I spared you that math part, since
> it's mostly in my head and not written already.
> Martin
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