World: r3wp

yes

whao...

So i have a difficult question : how do you handle intersection(s) 
between two paths ?

kib2: Note well.  
	either 0 [true][false]  ;== true
	either 1 [true][false]  ;== true

hence:
	either (modulo malong 2) [true][false]  ; == true, always...

kib, :-D
Do you expect me to remember, how postscript works. ;-)
I have to think a bit now ...

ahah

kib, I think, I remember the concept of paths in postscript. Can 
you give an example of such an intersection?

you're like me Geomol, after some months, my memory is garbage collected

LOL yes

I try to remember the really important things, the rest just hit 
the bin.

kib2: you can write:
	either (1 = modulo malong 2) [true][false]

In rebol, 0 is equivalent to true, not to false (as in many other 
languages).

Geomol if your memory works like mine, you only remember process 
and structures not contents

you remember abstract shapes, not data

well, I also remember data. I try to remember the important data.

like the greek alphabet. Doh! ;-)

all is data but the most important ones are data which build other 
data (rules) like in an inference engine

yes

Geomol: sorry, ....baby crying

Better to remember where do look something up, than to remember all 
that is in the book.

kib, np

exactly

i meant ie is there something for computing intersection between 
a line and a bezier path ?

better to know how to use a search engine (like google) instead of 
trying to remember all the url ;-)

kib, no there isn't much graphic routines in postscript, just box, 
boxfill, image and line:
http://www.fys.ku.dk/~niclasen/postscript/postscript.html

I have to check the original PostScript documentation to say, if 
those things are part of the definition of PS.

kib2, you mean intersection(s)* between a line and a bezier path.

Anton: yes, I've forgotten the (s)

It must be a fairly complex algorithm..

Anton: yes, that's why I was asking if someone else already wrote 
something like that. Computing such things much be a real headache 
!

if i had to do, i will use the draw engine with logical bitmap operators 
to find the points

it would be not really accurate but it would work

kib, I took a look at the PS documentation, and it has arcs, curves, 
etc. This isn't implemented in the REBOL ps dialect (yet). My dialect 
was just make fast to get some useful postscript out from REBOL.


I have a book on computer graphics, that might deal with the problem, 
you describe. I take a look ...

Geomol: thanks. Are you also the author of the PDF dialect ?

no, that's Gabriele, I think.

Gabriele is author of pdf-maker, yes.

I would not rest until I had computed the exact intersection(s) of 
line and bezier curve ! :)

Let's see, chapter 7, "Intersection in 2D". "7.3 Linear Components 
and Quadratic Curves", "7.4 Linear Components and Polynomial Curves". 
Hmm

Bezier curves are polynomial curves, so I guess that chapter 7.4 
has the answer.

you should be well informed, it's a dark matter

The book is called "Geometric Tools for Computer Graphics" by Philip 
J. Schneider and David H. Eberly.

:-)

Geomol: Worth a look ?

I think, it's an excellent book. I read about it on the web long 
ago, people discussing different books dealing with geometrical problems 
in computer graphics. I bought it back then and have used it often 
since.

Chapter 7.4 starts with "This section discusses how to compute points 
of intersection between the line and curve from both an algebraic 
and geometric perspective."

Taking some time to read and understand the chapter, I would guess, 
it wouldn't be too hard to construct an algorithm, that did the job.

Geomol: interesting....

what i don't understand, is your need to fulfill intersection points 
to postcript format, can't you send just an image of your drawnings 
?

Just realized, David H. Eberly is also the author of a book called 
"3D Game Engine Design". I should get this.