On 07-Sep-08 12:47, Chris B wrote:
> 
> "Thomas de Groot" <t.d### [at] internlDOTnet> wrote in message 
> news:48c3964b@news.povray.org...
>> Once in a while I try to solve this puzzle, but I give up. It is 
>> beyond my skills.
>>
>> How would one model this pavement in POV-Ray? It looks simpler than it 
>> is as - obviously - the inner arc of a row of stones is smaller than 
>> the outer arc. In RL (as on the examples below) this is constantly 
>> compensated I suppose to keep the pattern regular and symmetrical....
>>
> 
> I would think that the key distances of any significance in the sample 
> picture you posted are the radius of the outer edge of an arc and the 
> centre to centre distance.  In your image I would think that the stick 
> is used to keep the outer radius constant and that the strings keep the 
> centre to centre distance constant (and, in this instance the lines 
> straight). The radius of the inner edge is already set by the previous 
> arc of stones and would be used only as a guide to pick a block of the 
> right depth.
> 
> To get a good join, the tangent to one arc should pass through the 
> centre of the other arc (and visa versa) so that you get a right angle 
> at the joins and you can use a square block there to give a perfect 
> join. This means that the centre to centre distance would have to be the 
> Radius times the square root of 2.
> 
I am not sure if I understand what you mean. But let me put it in a way 
that I can understand. There are two special stones. One is at the end 
of one arc and at the beginning of the next one. The other is the one in 
the middle of an arc. Referring to my picture, the latter is the highest 
one in the arc and has a horizontal lower line. The other is 45 degrees 
turned. No matter how you position the other stones. The corner one 
advances sqrt(2) times the side of that stone every arc. The middle one 
can only advance by the side of that stone. So you'll end up with 41% 
space between the center stones of two consecutive arcs . That does not 
happen in real life. Either because not all stones have the same size or 
they are cheating in another way.

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