On 22-6-2017 13:50, Bald Eagle wrote:
> Thomas de Groot <tho### [at] degrootorg> wrote:
> 
>> This is a nice try but... it is not a /stacking/ of stones. It is a
>> crackled volume. If you drop stones, they will behave differently from
>> what you see here.
> 
> Indeed - it wasn't really even supposed to be a "try" - it was just a blatant
> cut&paste with a minor tweak or two to get it to run and close up the gaps a bit
> - to show that with a wee bit of POV-Ray magic, a 3-dimensional Voronoi diagram
> that gives the appearance of a pile of "stones" is THAT quick and easy - no
> math, no (user-written) algorithms, no staying up late, pulling out one's
> (remaining) hair, no crying in the corner because you're stoopid.
> 
> And to pick nits, if you drop stones, they will of course [sic] behave
> differently than if you stack them.
> 
> AND the end result is going to be a product of however the user codes the scene
> anyway, will will be a further layer of deviation from reality.
> 
> I'd say we're at a juncture where the parameters of the project need to be
> defined.  But there still all sorts of fun variations on the theme that we can
> play with - unconstrained by the prof.   :)
> (which is what the _really_ good students ought to be doing along the way / in
> addition to the stated project)
> 
> "So, I made that rock pile that you wanted - but I also did a few old Scottish
> castles, the Great Wall of China, a cross-section of an archaeological
> excavation site with some fossil meshes thrown in, an animated exploding Rice
> Krispy treat, the rubble in the aftermath of a Kalifornia earthquake, and I've
> begun a study on the kinetics of settling in a mixture of sand, aggregate, and
> cement in pre-mixed concrete....... by the way is there any more coffee?"
> ;)
> 
> 

I can only agree with you :-)

To tell the truth, I was not criticising your crackle which is fine by 
itself and useful in other contexts (a mortared wall?) I wanted to draw 
attention (mine included) to the very different geometry presented by 
stacking stones. Obvious, and yet something to ponder deeply for 
modelling purposes. :-)

-- 
Thomas

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On 6/23/2017 7:37 AM, Thomas de Groot wrote:
> To tell the truth, I was not criticising your crackle which is fine by
> itself and useful in other contexts (a mortared wall?) I wanted to draw
> attention (mine included) to the very different geometry presented by
> stacking stones. Obvious, and yet something to ponder deeply for
> modelling purposes. :-)

I've spent two days making rocks and trying to lay them in a single 
layer. I'm really struggling with it.

-- 

Regards
     Stephen

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On 23-6-2017 12:09, Stephen wrote:
> On 6/23/2017 7:37 AM, Thomas de Groot wrote:
>> To tell the truth, I was not criticising your crackle which is fine by
>> itself and useful in other contexts (a mortared wall?) I wanted to draw
>> attention (mine included) to the very different geometry presented by
>> stacking stones. Obvious, and yet something to ponder deeply for
>> modelling purposes. :-)
> 
> I've spent two days making rocks and trying to lay them in a single 
> layer. I'm really struggling with it.
> 

Yes it is a very difficult task, especially considering how easily 
Mother Nature does it herself. ;-)

Steering clear from specialised modelling packages which can do this, 
and trying to restrict myself to only POV-Ray, trace() is an obvious 
tool but it needs to be completed with some kind of gravity (vertical; 
trace -y) and/or stream energy (horizontal; trace +/-x or +/-z) control 
to settle individual grains before, during, and after impacts over a 
number of incrementing iterations. Not easy!

-- 
Thomas

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On 23-6-2017 13:21, Thomas de Groot wrote:
> Steering clear from specialised modelling packages which can do this, 
> and trying to restrict myself to only POV-Ray, trace() is an obvious 
> tool but it needs to be completed with some kind of gravity (vertical; 
> trace -y) and/or stream energy (horizontal; trace +/-x or +/-z) control 
> to settle individual grains before, during, and after impacts over a 
> number of incrementing iterations. Not easy!
> 

Something like this would be nice :-o

https://www.deltares.nl/academy/delft3d-4-modelling-sediment-transport-and-bed-dynamics/

-- 
Thomas

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I will just say that there apparently has been much work done on exactly this.

Makes for some very interesting reading.

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On 23-6-2017 21:19, Bald Eagle wrote:
> 
> I will just say that there apparently has been much work done on exactly this.
> 
> Makes for some very interesting reading.
> 
> 

Coastal engineering in the Netherlands has a worldwide reputation. 
However, I do not think that they model/stack the sand grains 
individually like we would like to do, and in fact that is far less 
interesting for their purpose. What they model are the different scale 
sediment transport mechanisms under variable space/time/sediment 
availability/composition conditions.

-- 
Thomas

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Am 2017-06-23 06:09, also sprach Stephen:

> I've spent two days making rocks and trying to lay them in a single 
> layer. I'm really struggling with it.
> 

I thought about it a little. I can easily do this in an animation, 
because of the constant recursive adjustments and tweaking of positions. 
  Building a single static image with everyone in the right place, not 
so much.

-- 
dik

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Thomas de Groot <tho### [at] degrootorg> wrote:

> > I will just say that there apparently has been much work done on exactly this.

Whoops - by "this", I meant the original objective.

I suppose that's the old / whole problem with pronouns, and I didn't want to
just hand out the links I was perusing - just yet.  ;)

I figured we'd see how Ari was coming along on this.

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On 26-6-2017 13:38, Bald Eagle wrote:
> Thomas de Groot <tho### [at] degrootorg> wrote:
> 
>>> I will just say that there apparently has been much work done on exactly this.
> 
> Whoops - by "this", I meant the original objective.
> 
> I suppose that's the old / whole problem with pronouns, and I didn't want to
> just hand out the links I was perusing - just yet.  ;)
> 
> I figured we'd see how Ari was coming along on this.
> 
> 
> 

I'll sit back and watch :-)


-- 
Thomas

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http://www.afhalifax.ca/magazine/wp-content/sciences/EmpilementDeDisques/ProducingPacking/Initialization.pdf

and

https://arxiv.org/pdf/1005.0011.pdf

 "For generally
shaped particles, finding the densest packings is notoriously difficult. This
salient point is

we
cannot guess or even closely approximate the answer, let alone prove it, and it
is difficult to
develop even a qualitative understanding of the effects of grain shape on

Until recently, very little was known about the densest packings of polyhedral
particles. The
difficulty in obtaining dense packings of polyhedra is related to their complex
rotational
degrees of freedom and to the non-smooth nature of their shapes [28, 29]."

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