"Peter Popov" <pet### [at] vipbg> wrote in message
news:nl34stcs8gm8pve5cb98o9vg5kuifhi5mc@4ax.com...
> Michael,
>
> a few weeks ago I defended my BEng final project on elastic deformable
> body dynamics. I am waiting for the 3.5 stable release to start
> working on patching what I've done into POV. Drop me a line if you
> need some geeky info.
>
>
Cool.  Thanks for the offer.  I think the framework I've got now is pretty close
to done.  I just need to add info to keep track of orientation and make sure the
algorithm works with whatever I give it.

I'm personally not a fan of using patched POV for highly specialized stuff (like
gels) because I think macros are more flexible, but it is much faster once it's
done.  Maybe the ClothRay and yours could be combined?  Of course, strings would
have to be added in too.  (simple - 1D cloths :-)  That would be great.  But,
then would POV-Ray be a ray-tracer or a simulation engine?

Again, thanks for the offer.  I might take you up on that.

Michael
--
#macro M(D,J)text{ttf"cyrvetic.ttf"D 1,0translate-J}#end#macro N(E,K)#local A=
M(E,K)light_source{-z*30rgb 1projected_through{A}}#end N("Michael"<1.6,-.2,5>)
N("Johnson"<1.9.8,5>)sphere{z*9,4pigment{gradient x+y scale 10color_map{[0 rgb
x][1rgb x+y]}sine_wave}} // (c)2001 Michael D Johnson red### [at] wvadelphianet

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"Mahalis" <don### [at] fakeycom> wrote in message
news:3bc1807d$1@news.povray.org...
> Neat! I like how the shock waves travel up and down the object.
>
Thanks!  Once the simulation was done right, it did that all by itself!  I was
heartily impressed.  I always find it amazing that once I get done with all the
math stuff, the thing actually looks real.

Michael
--
camera{location<8,20>look_at<6,0,4>}light_source{<8,8>rgb 1}difference{union{
#macro M(D,J)#local R=asc(substr(D,J,1))-32;<div(R,10)*2,mod(R,10)>#end#macro
E(D,B,R)prism{-D,4+D,R#local C=1;#while(C<R+1)M(B,C)#local C=C+1;#end}#end E(
0," (2:FPKAD80* U_dZU"18)sphere{2,2}#macro T(N)cylinder{<9,-N,3><9,4+N,3>3-N}
#end T(0)}T(2)E(1"45LNXUK4"8)pigment{rgb x+y/2}}//(c)2001 MDJohnson(Redbeard)

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"Redbeard (MDJohnson)" wrote:

>  Otherwise it *would* be possible to fall
> through the surface.  In this case, the surface is a plane, and if the gel is
> falling too fast (or an element is) it might pass right through the plane and
> miss the trace check.

Yeah, it was say  1E-06 pov units from the floor and plummetting at the floor at a
breathtaking 1E-04 units/frame.  It seems silly, but I guess that was what was
happening, so I just shelved the whole idea.  My project was actually perfect
rolling/bouncing balls on a golf course...

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> I'm personally not a fan of using patched POV for highly specialized stuff
(like
> gels) because I think macros are more flexible, but it is much faster once
it's
> done.  Maybe the ClothRay and yours could be combined?  Of course, strings
would
> have to be added in too.  (simple - 1D cloths :-)  That would be great.
But,
> then would POV-Ray be a ray-tracer or a simulation engine?

Isn't ratracing simulation of light?

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ARTis wrote:

> Isn't ratracing simulation of light?

No. Ratracing is where you take two of more rats and have them compete
in a race. Betting is usually involved. :)

-- 
Ken Tyler

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> > Isn't ratracing simulation of light?
>
> No. Ratracing is where you take two of more rats and have them compete
> in a race. Betting is usually involved. :)

And what is rayacing? (:

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ARTis wrote:
> 
> > > Isn't ratracing simulation of light?
> >
> > No. Ratracing is where you take two of more rats and have them compete
> > in a race. Betting is usually involved. :)
> 
> And what is rayacing? (:

Raytracing is essentially shooting imaginary rays of light out into space.
When one of those imaginary rays of light intersects something a pixel color
is returned to the screen depending upon the shape, color, and surface
properties described for that object. One could call it the simulation
of light but it does not truly model the physical properties of light as
one would expect from a scientific light modelling program. Raytracing
deals more with object properties than it does light properties.
Certainly there is an overlap that occurs to accomplish this but I
don't think calling Raytracing a "simulation of light" an accurate all
encompassing statement.

-- 
Ken Tyler

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Rayacing is when a guy named Ray gets A++ in every class.

"ARTis" <art### [at] aaaapollolv> wrote in message
news:3bc2f823@news.povray.org...
>
> > > Isn't ratracing simulation of light?
> >
> > No. Ratracing is where you take two of more rats and have them compete
> > in a race. Betting is usually involved. :)
>
> And what is rayacing? (:
>
>

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On Mon, 8 Oct 2001 19:28:36 -0400, "Redbeard \(MDJohnson\)"
<red### [at] wvadelphianet> wrote:

>I've been using Hugo Elias' page (http://freespace.virgin.net/hugo.elias/) as a
>reference for my simulations.  He's got some pretty good info, and if you like
>to explore he doesn't give you *too* much.

Keep in mind that what is shown on Hugo's page is *the* most
simplistic way of doing deformable body dynamics simulation. Linear
mass-spring models are in general simpler than, say, finite element
models, but the former can be made very realistic with introducing
different improvements.

As a start, I'd recommend reading anything you can find on the
subject, esp. the works of Demetri Terzopoulos, David Baraff, Andrew
Wittkin, James O'Brien and Chen Wu.

>As for falling through the surface - I'm cheating right now.  If the
>y-coordinate is less than 0 + radius of element, it's forced to that value.
>When I start adding the ability to bounce off of surfaces I'll have to start
>using trace and being *very* careful.

Keep in mind that contact forces are *very* hard to model
realistically. Collisions are even harder, as impulse propagation in
this case is almost a stepwise process. In addition, inertia has to be
taken into account.

The geeky lingo above is to say that you can't just place some nodes
on the surface they will collide with and expect realistic results.

Maybe I'm just jealous (gelous?). Again someone beat me to it :)

Keep up the good work!

 
Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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"Peter Popov" <pet### [at] vipbg> wrote in message
news:jsfastgausb9ouu35jhbp7a5shefje1oi9@4ax.com...
> On Mon, 8 Oct 2001 19:28:36 -0400, "Redbeard \(MDJohnson\)"
> <red### [at] wvadelphianet> wrote:
>
> >I've been using Hugo Elias' page (http://freespace.virgin.net/hugo.elias/) as
a
> >reference for my simulations.  He's got some pretty good info, and if you
like
> >to explore he doesn't give you *too* much.
>
> Keep in mind that what is shown on Hugo's page is *the* most
> simplistic way of doing deformable body dynamics simulation. Linear
> mass-spring models are in general simpler than, say, finite element
> models, but the former can be made very realistic with introducing
> different improvements.
>
I do realize that (I was an engineering major and was exposed to some FEM) but
I'm not really looking for *super* realistic right now.  In fact, the animation
I was working for IRTC (which I still hope to finish, though not in time for the
contest) is going to use the gel to do a *very* unrealistic construction of a
bridge :-)

> As a start, I'd recommend reading anything you can find on the
> subject, esp. the works of Demetri Terzopoulos, David Baraff, Andrew
> Wittkin, James O'Brien and Chen Wu.
Thanks.  I'll check into them.

> >As for falling through the surface - I'm cheating right now.  If the
> >y-coordinate is less than 0 + radius of element, it's forced to that value.
> >When I start adding the ability to bounce off of surfaces I'll have to start
> >using trace and being *very* careful.
>
> Keep in mind that contact forces are *very* hard to model
> realistically. Collisions are even harder, as impulse propagation in
> this case is almost a stepwise process. In addition, inertia has to be
> taken into account.
Again, I'm not looking for full realism, just something that looks good in an
animation.  I will probably have to cheat at most steps by introducing abitrary
forces.  The sotrage format I'm using takes that into account.

> The geeky lingo above is to say that you can't just place some nodes
> on the surface they will collide with and expect realistic results.
Yep.

> Maybe I'm just jealous (gelous?). Again someone beat me to it :)
>
> Keep up the good work!
Thanks!  In fact, while I was away I figured out something that is wrong with my
model.  I hope to fix it over the weekend (now that beta 6 is out - thanks
Chris)

Michael

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