Remco de Korte <rem### [at] xs4allnl> wrote in

>I have already posted an mpeg version.
>I didn't really remember what codec I used. 
>I created the AVI with Fast Movie Processor 

I cannot really claim to know this stuff - like I mentioned, the paperplane 
was my first animation (discounting the tutorial) - but try VideoMach. It 
is a successor of the Fast Movie Processor, and it supports .png as input 
format, and mpeg1 (among others) as output. And most importantly for me 
it's easy to use...

>> Actually, it could possibly be done with meshes even in normal
>> POV-Ray, but it would have been a bit messy: You can apply textures to
>> individual triangles, just make a "hollow" paper, where the top and
>> bottom surfaces meet only at folding points, and are something like
>> 0.000001 apart at maximum.

>The problem with this approach is that you can 
>have folds crossing each other so it would be 
>rather difficult to calculate the triangles 
>(at least to me).

What I did was first fold the a real paperplane, unfold it and draw the 
creases on graph paper. Then it was time for some head-banging and 
trigonometry to find out the points where the creases cross each other or 
the edge of the paper. This process was much aided by rendering each 
relevant set of triangles (one set per area delimeted by creases) in a 
different color while having the "paper" in it's unfolded state. Easy 
visual verification for having the points right.

>There is something else, which I saw you also
>handled really well: the thickness of the 
>paper and the room between folds. I don't know 
>how you did it but it took me quite some 
>trial and error to get it right.

Thanks! It wasn't the hard part, really. Once I had the points (vectors) 
declared I used a simple macro to rotate the relevant points around the 
fold-lines. The hard part was the topology of the paper: which fold folds 
when, where and around what.

Also, I cheated:

A) only the "right" side of the plane is really modelled, the left side is 
just a copy of the right scaled <-1, 1, 1>. B) a couple of points along the 
center-line are checked to see if they have crossed to the wrong side. If 
they have, they are returned to the center line. If I didn't do this the 
paper would "tear" on a couple of points.

Yours,

 -- Nikodemus

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