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From: Jim Holsenback
Subject: Filling a hourglass with sand?
Date: 21 Feb 2010 12:24:43
Message: <4b816c5b@news.povray.org>
Hola,

Looking for suggestions on how to fill a hourglass with sand. So far my 
attempt(s), (macro placing grains bounded_by hourglass shape), isn't giving 
any joy. Wasn't there a bowl of cheerios example floating around somewhere? 
If not, maybe I was thinking of something else!

Jim
BTW: want all the sand to be at the bottom


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From: Alain
Subject: Re: Filling a hourglass with sand?
Date: 21 Feb 2010 14:07:19
Message: <4b818467@news.povray.org>

> Hola,
>
> Looking for suggestions on how to fill a hourglass with sand. So far my
> attempt(s), (macro placing grains bounded_by hourglass shape), isn't giving
> any joy. Wasn't there a bowl of cheerios example floating around somewhere?
> If not, maybe I was thinking of something else!
>
> Jim
> BTW: want all the sand to be at the bottom
>
>

Do you want to place each *grain* individualy?
If so, fist, you create a reference object. Is must be a shell slightly 
smaller than the hourglass and have a relatively small thickness. That 
object will have the shape of the sand.
Then, you randomly chose points in it's bounding box and do an inside 
test. Keep trying until the point is inside the shell then place an 
object. You probably don't need to prevent the grains from intersecting, 
so, you can probably skip any colision test.
At each point, you place one grain: a sphere, a randomly rotated box or 
a small mesh, also randomly rotated.
You will probably end up with a few 1000000 objects. Put them all in a 
single union and use a single texture for the whole union.

The best way would be to have a single object very slightly smaler than 
the part where you want the sand to be. It can be a lathe or sor object 
intersected with a height_field.
Then, the trick is to create a nice sand texture.



Alain


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From: Jim Holsenback
Subject: Re: Filling a hourglass with sand?
Date: 21 Feb 2010 14:49:33
Message: <4b818e4d@news.povray.org>
"Alain" <aze### [at] qwertyorg> wrote in message 
news:4b818467@news.povray.org...
> Then, you randomly chose points in it's bounding box and do an inside 
> test. Keep trying until the point is inside the shell then place an 
> object.

ah ... thanks for the clarity I think this is what I was overlooking.

merci


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From: Darren New
Subject: Re: Filling a hourglass with sand?
Date: 21 Feb 2010 15:22:57
Message: <4b819621$1@news.povray.org>
Alain wrote:
> If so, fist, you create a reference object. Is must be a shell slightly 
> smaller than the hourglass and have a relatively small thickness. That 
> object will have the shape of the sand.

Also, unless your sand is semi-transparent or something, you can't see sand 
inside other sand. So you can build a punt[1] on the bottom to reduce the 
number of independent grains.

You might also want to perhaps do something to make sure you don't have 
grains floating in mid-air, or to make a higher hill in the middle in order 
to make it look like it poured in through the neck of the glass.


[1] http://www.glassblower.info/images/punt-indentation-wine-bottle.jpg

-- 
Darren New, San Diego CA, USA (PST)
   The question in today's corporate environment is not
   so much "what color is your parachute?" as it is
   "what color is your nose?"


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From: Jim Holsenback
Subject: Re: Filling a hourglass with sand?
Date: 21 Feb 2010 16:10:50
Message: <4b81a15a@news.povray.org>
"Darren New" <dne### [at] sanrrcom> wrote in message 
news:4b819621$1@news.povray.org...
> Also, unless your sand is semi-transparent or something, you can't see 
> sand inside other sand. So you can build a punt[1] on the bottom to reduce 
> the number of independent grains.

well ... learned something ... knew about pontil, but not punt (so that's 
what they call it). hey maybe that'll save me a quarter million grains or so 
;-)

posted what i have so far in images.

Jim


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