d57nnr$hr5$1@chho.imagico.de...
> Note this is more 'scanline rendering' than raytracing.  For raytracing 
> you would position the 'string' to one pixel of the 'image' after the 
> other and look into the 'scene' where it points at.  Here the string is 
> positioned in the scene and from there you look where it intersects the 
> image.

Well, given the technology shown here, it couldn't be "raytracing" stricto 
sensu obviously. The interesting thing is that these people were already 
creating pictures using analog rays instead of digital ones.

I couldn't find my book but here's a more detailed explanation:
http://www.vam.ac.uk/images/5166-popup.html

"A pointer is attached to a thread running through a pulley on the wall. The 
thread represents a ray of light passing through the picture plane to the 
theoretical eye-point denoted by the pulley. As one man fixes key points on 
the lute, his assistant records the vertical and horizontal co-ordinates of 
the thread as it passes through the frame, and plots each new point to 
create a drawing. The principle is correct, but the procedure is complicated 
and rarely produced good results. "


G.

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