(Apologies for originally posting on p.a. - it looked like p.b.a to my
tired eyes...)

OK, I've been trying out the Mechsim part of Megapov, and I'm running
into problems.  Could anyone explain why the fourth domino is
"transparent" to the one that should push it over, but everything else
works?  Here's the topology block I'm using:

topology {

#declare Move = transform {rotate <0,90,10> translate <2,0.001,0.001>}

group {MechSim_Generate_Box(<0,0,0>, 0.025, 100, 20000, 5000, true,
<0.25,0.25,0.05>, <3,5,3>, Move, 3)}

#declare loop = 0;
#while (loop < 5)

    #declare Move = transform {rotate <0,90,0> translate
<1.5-(loop*0.5),0.001,0>}

    group {MechSim_Generate_Box(<0,0,0>, 0.025, 100, 20000, 5000, true,
<0.25,0.25,0.05>, <3,5,3>, Move, 3)}

    #declare loop = loop + 1;
    #end

save_file "dominoes.mech"
}

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Attachments:
Download 'Dominoes.m1v.mpg' (235 KB)

"Andrew" <ast### [at] hotmailcom> wrote in message
news:3e3c2a58@news.povray.org...
> (Apologies for originally posting on p.a. - it looked like p.b.a to my
> tired eyes...)
>
> OK, I've been trying out the Mechsim part of Megapov, and I'm running
> into problems.  Could anyone explain why the fourth domino is
> "transparent" to the one that should push it over, but everything else
> works?  Here's the topology block I'm using:
>
> topology {
>
> #declare Move = transform {rotate <0,90,10> translate <2,0.001,0.001>}
>
> group {MechSim_Generate_Box(<0,0,0>, 0.025, 100, 20000, 5000, true,
> <0.25,0.25,0.05>, <3,5,3>, Move, 3)}
>
> #declare loop = 0;
> #while (loop < 5)
>
>     #declare Move = transform {rotate <0,90,0> translate
> <1.5-(loop*0.5),0.001,0>}
>
>     group {MechSim_Generate_Box(<0,0,0>, 0.025, 100, 20000, 5000, true,
> <0.25,0.25,0.05>, <3,5,3>, Move, 3)}
>
>     #declare loop = loop + 1;
>     #end
>
> save_file "dominoes.mech"
> }

At a guess, I'd say the problem is that the third domino is hitting the fourth with
the most
force out of all of them, and the settings somehow aren't correct, so domino 3 goes
inside
domino 4. I still mainly guess what settings to use when I use mechsim, so I can't say
for
definite, but it could be that your step is not small enough.

If this doesnt help, then probably better waiting for Christoph to reply.

All the best,

Andy Cocker

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> At a guess, I'd say the problem is that the third domino is hitting
the fourth with the most
> force out of all of them, and the settings somehow aren't correct, so
domino 3 goes inside
> domino 4. I still mainly guess what settings to use when I use
mechsim, so I can't say for
> definite, but it could be that your step is not small enough.
>
> If this doesnt help, then probably better waiting for Christoph to
reply.
>
> All the best,
>
> Andy Cocker


I hadn't considered that.  I think I am using a fairly large step, but
the calculation time is already large, and I plan to use more dominoes
than this.  I guess I'll play around with the settings a bit and see if
I can make the dominoes with less masses.

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I have another question to add here.  I intend to make quite a large
number of dominoes, but it seems that the calculations will become
prohibitively complicated.  The best I can do to reduce this is to form
two groups of dominoes, domino number n being in group number mod(n,2).
But this still means that each mass will be tested against half of the
total number - obviously very inefficient in this case where only the
neighbouring dominoes matter.  Is there any better way of doing this?

If not, then perhaps a feature request would be in order:  Allow each
group to specify which other groups it interacts with, as opposed to
interacting with every other group but itself (in collision mode 2).  I
don't know whether this would be a trivial modification, though I
suspect it would already be a feature if it were :)  But it sure would
be useful for scenes like this, although I think I've picked a
near-worst-case-scenario here.

Post a reply to this message

Andrew wrote:
> 
> OK, I've been trying out the Mechsim part of Megapov, and I'm running
> into problems.  Could anyone explain why the fourth domino is
> "transparent" to the one that should push it over, but everything else
> works?  Here's the topology block I'm using:

This does not help finding the problem, you should post the whole scene
(but please make it small).

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 31 Dec. 2002 _____./\/^>_*_<^\/\.______

Post a reply to this message

Andrew wrote:
> 
> [...]
> 
> If not, then perhaps a feature request would be in order:  Allow each
> group to specify which other groups it interacts with, as opposed to
> interacting with every other group but itself (in collision mode 2).  I
> don't know whether this would be a trivial modification, though I
> suspect it would already be a feature if it were :)  But it sure would
> be useful for scenes like this, although I think I've picked a
> near-worst-case-scenario here.

I will consider it.  

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 31 Dec. 2002 _____./\/^>_*_<^\/\.______

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If you watch carefully the fourth Domino is actually very slightly affected
by the third before the second one knocks it over.

Another thing I note that in your anim the Domino's are flexible... where as
in real life they aren't, well none I've seen are.  :)  I'm not sure about
Megapov or the mechsim part but I assume you can set the HARDNESS of an
object?

> OK, I've been trying out the Mechsim part of Megapov, and I'm running
> into problems.  Could anyone explain why the fourth domino is
> "transparent" to the one that should push it over, but everything else
> works?  Here's the topology block I'm using:



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> Another thing I note that in your anim the Domino's are flexible...
where as
> in real life they aren't, well none I've seen are.  :)  I'm not sure
about
> Megapov or the mechsim part but I assume you can set the HARDNESS of
an
> object?

Yes, they were a bit flexible weren't they :)  Mechsim works using
masses connected by springs rather than shapes like boxes and spheres.
The dominoes here were grids of masses, several to a side, and the
springs between them were simply not stiff enough to make them look
rigid.

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