Keith,
> Le 26 nov. 2020 à 12:12, Keith McKay <mckaymeis...@gmail.com> a écrit :
> Thanks Fabrice and Hans.
>
> I now see I can simplify some lines of the code:
>
> pp := ((xpart a[i])/cf*cm, (ypart a[i])/cf*cm); now becomes pp:= a[i];
>
> and
>
> pp := pp --- ((xpart a[i+1]/cf)*cm, (ypart a[i+1])/cf*cm); now becomes pp :=
> pp --- a[i +1] ;
>
> However I still have the problem in the calculation of xcoord and ycoord
> which are used in the creation of path pp:
>
> for squig = 1 step 1 until 15:
>
> xcoord := uniformdeviate(1) - 0.5 + (xpart a[i]/cf);
>
> ycoord := uniformdeviate(1) - 0.5+ (ypart a[i]/cf);
>
> pp := pp .. {curl 100}(xcoord*cm, ycoord*cm);
>
> endfor;
>
> I'm adding a small random amount to the x and ypart of the pair a[i] to
> produce a path that is like a squiggle (gribouiller in French, according to
> Google). I have to use cf to convert to the x and yparts to centimeters since
> they seem to loose the centimeter units on separation. I can't see anyway
> round this, or am I missing something?
>
> Thanks
> Keith McKay
First « uniformdeviate(1) - 0.5 » could be modified to « uniformdeviate(0.5)».
To add noise, you can use the randomized function of Metafun. For exemple, you
can write:
draw pp randomized 1cm ;
Fabrice.
>
> On 26/11/2020 15:19, Fabrice L wrote:
>> Hi keith,
>>
>>> Le 26 nov. 2020 à 10:09, Keith McKay <mckaymeis...@gmail.com
>>> <mailto:mckaymeis...@gmail.com>> a écrit :
>>>
>>> Hi,
>>>
>>> I have been using xpart and ypart to extract these values from pairs of
>>> points in a path but I wasn't getting the correct result. I was expecting:
>>>
>>> pair (2cm, 11cm) to give xpart 2 and ypart 11
>>>
>>> However I was getting:
>>>
>>> pair (2cm, 11cm) -> xpart 56.6929 and ypart 311.8096
>>>
>>> After much head scratching and reading the MetaPost and MetaFun manuals, I
>>> realised that the units of xpart or ypart are in Postcript points or Big
>>> Points (bp), and 1 bp is 1/72 of an inch, and thus to get the values of
>>> xpart or ypart in cm I would have to use a correction factor. I had made
>>> the assumption that since the x and ypart in the pair was in cm that the
>>> result would be in cm, but I see now that this is not the case. Will I have
>>> to continue doing this or is there some magic within MetaFun which takes
>>> account of the units in a pair and outputs the result of x and ypart in the
>>> same units?
>>>
>>> The MWE belows shows what I have been doing.
>>>
>>> Thanks
>>>
>>> Keith McKay
>>>
>>> %%% MWE %%%
>>> \setuppapersize [A5, landscape][A4, portrait]
>>> \usecolors[crayola]
>>> \starttext
>>> \startMPpage
>>> StartPage;
>>> width := PaperWidth ; height := PaperHeight ; unit := cm ;
>>> numeric squig;
>>> pair a[]; a0 = (2cm,11cm); a1 = (4cm,10cm); a2 = (6cm,9cm); a3 =
>>> (8cm,8cm);
>>> show xpart a[0], ypart a[0]; %Example of result from x and ypart before
>>> applying correction factor (cf) %
>>> cf := 72/2.54; %Converts points/in to points/cm%
>>> path pp;
>>> for i = 0 step 1 until 3:
>>> pp := ((xpart a[i])/cf*cm, (ypart a[i])/cf*cm);
>>> for squig = 1 step 1 until 15:
>>> xcoord := uniformdeviate(1) - 0.5 + (xpart a[i]/cf);
>>> ycoord := uniformdeviate(1) - 0.5+ (ypart a[i]/cf);
>>> pp := pp .. {curl 100}(xcoord*cm, ycoord*cm);
>>> endfor;
>>> pp := pp --- cycle;
>>> if i < 3 :
>>> pp := pp --- ((xpart a[i+1]/cf)*cm, (ypart a[i+1])/cf*cm);
>>> fi;
>>> f :=((1.4 - 0.6) * uniformdeviate(1)) + 0.8; % Factor to lighten/darken
>>> colour %
>>> draw pp withpen pencircle xscaled 0.5mm yscaled .1mm rotated 45
>>> withcolor (f[white,\MPcolor{BurntSienna}]);
>>> endfor;
>>> StopPage;
>>> \stopMPpage
>>> \stoptext
>>> %%%%%%%%%%%%%%
>>>
>>
>> MetaPost (MetaFun) is taking care of everything regarding units. As you ave
>> discovered, everything is translated to a unique internal dimension. So you
>> can write:
>>
>> a := (1cm,2in) ;
>>
>> with no problem. The « cm » and « in » parts of the expression will become
>> numbers to translate this number on the right unit.
>> Fabrice.
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