Hi guys

I want to somehow drop spheres into a box, and someone on pov.general
suggested that I use megapov's mechsim function. I have taken a look at it,
but it looks quite involved... am I correct in stating the following, and
if not, why:

1. The mechsim functions can only work with iso-surfaces. I cannot, for
example, construct a "container" / constraining set of surfaces from CSG,
and expect it to work. Is this wrong or right?

2. The mechsim functions are uni-axial - don't know how to express this...
let's say my "container" looks liks this:

|      |
|      |
|      |
|------|

It seems there is no way to do this with mechsim:

|     o|
|oooooo|
|oooooo|
|------|

o = sphere

but the result will be this:

|     o|
|oooooo|
|oooooo|oooo
|------|oooooo
----------------

I.e  can I constrain masses in the Z axis (the "bottom" of the holder) AND
the sides (say, in the X axis).? I. e. can I use two axises for constraints
and reactions? One being the apparently easily defined mechsim plane, and
the other the "inner" surfaces of an isosurface containing the masses?

3. How about a circular container (like containing masses in a cylinder?)
This seems exactly what Christoph Hormann did in one of the images on his
site (if I'm not being an idiot), but I'm buggered if I can even begin to
envision the syntax for that.

4. Non - circular masses? I know about bars, but can you use another
isosurface or a well-behaved mesh with an in and outside? I. e. use
something other than a sphere or a bar as a visual representation for a
mass?

5. Mechsim works exclusively in animations - if I thus want to use it in a
scene, I will need to setup animation parameters and pick a certain frame
where the mechanical simulation has progressed to the point I want. Mechsim
is useless outside an animation. Is it possible to simulate a bar deform,
for example, at its "halfway" point, -without- using an animation...?

If I am asinine or not worth answering, does anybody have a pointer to any
tutorials or docs except those that already come with MegaPov? I'd like
some more info than the examples provide - not as a criticism of the docs,
of course, but merely because I need more info due to my own limitations
(especially mathematical, and regarding isosurfaces!) in understanding the
mechsim patch.

Thanks!
-- 
Stefan Viljoen
Software Support Technician / Programmer
Polar Design Solutions

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Stefan Viljoen <spamnot@ wrote:
> Hi guys
> 
> I want to somehow drop spheres into a box, and someone on pov.general
> suggested that I use megapov's mechsim function. I have taken a look at it,
> but it looks quite involved... am I correct in stating the following, and
> if not, why:
> 
> 1. The mechsim functions can only work with iso-surfaces. I cannot, for
> example, construct a "container" / constraining set of surfaces from CSG,
> and expect it to work. Is this wrong or right?

Wrong.  Both functions and objects are supported as environments.  Yet 
there are good reasons for using functions (as outlined in the docs).

> [...]
> 
> I.e  can I constrain masses in the Z axis (the "bottom" of the holder) AND
> the sides (say, in the X axis).? I. e. can I use two axises for constraints
> and reactions? One being the apparently easily defined mechsim plane, and
> the other the "inner" surfaces of an isosurface containing the masses?

Sorry but i have no idea what you are talking about.  A sample scene 
with explanation what should work differently might be helpful.

> 4. Non - circular masses? I know about bars, but can you use another
> isosurface or a well-behaved mesh with an in and outside? I. e. use
> something other than a sphere or a bar as a visual representation for a
> mass?

As explained in the docs you can build up arbitrarily complex shapes 
from masses, connections and faces.  mechsim.inc contains macros for 
some basic ones (blocks, patches and lines).  How you visualize the 
simulation results is up to you (mechsim.inc contains macros for this as 
well).

> 5. Mechsim works exclusively in animations

No.  The mechsim patch in fact works completely independent from the 
animation feature (although you can of course use the clock variable).

> If I am asinine or not worth answering, does anybody have a pointer to any
> tutorials or docs except those that already come with MegaPov?

In fact the sample and tutorial scenes already contain several examples 
quite close to 'filling spheres into a container'.  tutorial03.pov and 
glow_sim.pov in particular might be useful (in combination with 
simulation method 4).

Christoph

-- 
POV-Ray tutorials, include files, Landscape of the week:
http://www.imagico.de/ (Last updated 31 Oct. 2005)
MegaPOV with mechanics simulation: http://megapov.inetart.net/

Post a reply to this message

Christoph Hormann spake:

> Stefan Viljoen <spamnot@ wrote:
>> Hi guys
>> 
>> I want to somehow drop spheres into a box, and someone on pov.general
>> suggested that I use megapov's mechsim function. I have taken a look at
>> it, but it looks quite involved... am I correct in stating the following,
>> and if not, why:
>> 
>> 1. The mechsim functions can only work with iso-surfaces. I cannot, for
>> example, construct a "container" / constraining set of surfaces from CSG,
>> and expect it to work. Is this wrong or right?

Hi Christoph,
 
> Wrong.  Both functions and objects are supported as environments.  Yet
> there are good reasons for using functions (as outlined in the docs).

I did read the doc well before posting - I'll just go and take a look again.
 
>> [...]
>> 
>> I.e  can I constrain masses in the Z axis (the "bottom" of the holder)
>> AND the sides (say, in the X axis).? I. e. can I use two axises for
>> constraints and reactions? One being the apparently easily defined
>> mechsim plane, and the other the "inner" surfaces of an isosurface
>> containing the masses?
> 
> Sorry but i have no idea what you are talking about.  A sample scene
> with explanation what should work differently might be helpful.

Hehe - no need. I went and rendered every mechsim animation in the
distribution archive, and I see that the question is irrelevant. I'll just
try to figure out how the syntax connects to what I see on the screen.
 
>> 4. Non - circular masses? I know about bars, but can you use another
>> isosurface or a well-behaved mesh with an in and outside? I. e. use
>> something other than a sphere or a bar as a visual representation for a
>> mass?

> As explained in the docs you can build up arbitrarily complex shapes
> from masses, connections and faces.  mechsim.inc contains macros for
> some basic ones (blocks, patches and lines).  How you visualize the
> simulation results is up to you (mechsim.inc contains macros for this as
> well).

Ok - I'll see if I can figure it out...
 
>> 5. Mechsim works exclusively in animations
> 
> No.  The mechsim patch in fact works completely independent from the
> animation feature (although you can of course use the clock variable).

Hmm.
 
>> If I am asinine or not worth answering, does anybody have a pointer to
>> any tutorials or docs except those that already come with MegaPov?
 
> In fact the sample and tutorial scenes already contain several examples
> quite close to 'filling spheres into a container'.  tutorial03.pov and
> glow_sim.pov in particular might be useful (in combination with
> simulation method 4).

I rendered all of them, I'll just have to puzzle out the syntax myself then.
 
> Christoph

Thanks for the reply! 

Regards,
-- 
Stefan Viljoen
Software Support Technician / Programmer
Polar Design Solutions

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