Drawing oriented paths in MetaFun

Drawing oriented paths in MetaFun

[Giuseppe Bilotta]

Does MetaFun provide some macro to draw oriented paths? I
would like it to basically add a small arrow *in the middle*
of the path? Such a macro

draworiented somepath somespecs ;

would have to act like

drawarrow firsthalf(somepath) somespecs ;
draw secondhalf(somepath) somespecs ;

Is it available already, or should I roll my own?

-- 
Giuseppe "Oblomov" Bilotta

Re: Drawing oriented paths in MetaFun

[Giuseppe Bilotta]

Wednesday, November 16, 2005 Giuseppe Bilotta wrote:

> Does MetaFun provide some macro to draw oriented paths? I
> would like it to basically add a small arrow *in the middle*
> of the path? Such a macro

> draworiented somepath somespecs ;

> would have to act like

> drawarrow firsthalf(somepath) somespecs ;
> draw secondhalf(somepath) somespecs ;

> Is it available already, or should I roll my own?


Hm. I came up with

def draworiented expr c =
  path _c_ ; _c_ := c ;
  do_draworiented
enddef ;

def do_draworiented text t =
  draw _c_ t ;
  drawarrow subpath(0, length(_c_)/2) of _c_ ;
enddef;
 
which works, although I have to do

draworiented (reverse p1)

Is there an easy way to have it work with

draworiented reverse p1 ?

-- 
Giuseppe "Oblomov" Bilotta

Re[2]: Drawing oriented paths in MetaFun

[Giuseppe Bilotta]

Wednesday, November 16, 2005 Giuseppe Bilotta wrote:

> Wednesday, November 16, 2005 Giuseppe Bilotta wrote:

>> Does MetaFun provide some macro to draw oriented paths? I
>> would like it to basically add a small arrow *in the middle*
>> of the path? Such a macro

>> draworiented somepath somespecs ;

>> would have to act like

>> drawarrow firsthalf(somepath) somespecs ;
>> draw secondhalf(somepath) somespecs ;

>> Is it available already, or should I roll my own?


> Hm. I came up with

> def draworiented expr c =
>   path _c_ ; _c_ := c ;
>   do_draworiented
> enddef ;

> def do_draworiented text t =
>   draw _c_ t ;
>   drawarrow subpath(0, length(_c_)/2) of _c_ ;
> enddef;
 
> which works, although I have to do

> draworiented (reverse p1)

> Is there an easy way to have it work with

> draworiented reverse p1 ?


Oh sorry it works ... however, it traces half of the curve
twice. So I came up with the next:

def draworiented expr c =
  path _c_ ; _c_ := c ;
  do_draworiented
enddef ;

def do_draworiented text t =
  drawarrow subpath(0, length(_c_)/2) of _c_ t ;
  draw subpath(length(_c_)/2, length(_c_)) of _c_ t ;
enddef;
 
This still isn't perfect, but it works. It needs a little
tuning so that the arrow is more centered, and of course it
could be improved to put the arrow at any arbitrary point on
the path.

-- 
Giuseppe "Oblomov" Bilotta

Re: Drawing oriented paths in MetaFun

[Hans Hagen]

Giuseppe Bilotta wrote:

>Wednesday, November 16, 2005 Giuseppe Bilotta wrote:
>
>  
>
>>Does MetaFun provide some macro to draw oriented paths? I
>>would like it to basically add a small arrow *in the middle*
>>of the path? Such a macro
>>    
>>
>
>  
>
>>draworiented somepath somespecs ;
>>    
>>
>
>  
>
>>would have to act like
>>    
>>
>
>  
>
>>drawarrow firsthalf(somepath) somespecs ;
>>draw secondhalf(somepath) somespecs ;
>>    
>>
>
>  
>
>>Is it available already, or should I roll my own?
>>    
>>
>
>
>Hm. I came up with
>
>def draworiented expr c =
>  path _c_ ; _c_ := c ;
>  do_draworiented
>enddef ;
>
>def do_draworiented text t =
>  draw _c_ t ;
>  drawarrow subpath(0, length(_c_)/2) of _c_ ;
>enddef;
> 
>which works, although I have to do
>
>draworiented (reverse p1)
>
>Is there an easy way to have it work with
>
>draworiented reverse p1 ?
>
>  
>
add another step (do_do_) , first pick up 'reverse p1' as expression, 
save that in a path variable, and then pick up the text

Hans

Re: Drawing oriented paths in MetaFun

[Hans Hagen]

Giuseppe Bilotta wrote:

>Does MetaFun provide some macro to draw oriented paths? I
>would like it to basically add a small arrow *in the middle*
>of the path? Such a macro
>
>draworiented somepath somespecs ;
>
>would have to act like
>
>drawarrow firsthalf(somepath) somespecs ;
>draw secondhalf(somepath) somespecs ;
>
>Is it available already, or should I roll my own?
>
>  
>
it's there; watch out, i just added a scaling option

\starttext

\setupcolors[state=start]

\startMPpage

vardef arrowheadonpath (expr p, s) =
  save autoarrows ; boolean autoarrows ; autoarrows := true ;
  set_ahlength(scaled ahfactor) ; % added
  arrowhead p if s<1 : cutafter (point (s*arclength(p)+.5ahlength) on p) fi
enddef ;

path p ; p := (0,0)--(10cm,10cm) ;

draw p withcolor red ;
ahfactor := 5 ; % default is 2.5
fill arrowheadonpath(p,.5) withcolor blue ; % try .25

currentpicture := currentpicture xsized (10cm) ;
\stopMPpage

\stoptext