[NTG-context] Re: enhancing MetaPost presentation progress graphics

[Taco Hoekwater <taco@bittext.nl>]

Hi,

First, find the actual point along the curve of the wave you want, then you can ask for the direction of the wave at that time, and its point:

\startuseMPgraphic{Waves}
numeric height,stops,yoffset;
stops := 10;
height := OverlayHeight/10;
path wave[]; % storing waves

draw (0,0)--(OverlayWidth,0)--(OverlayWidth,OverlayHeight) withcolor white withpen pencircle scaled 0.01;

for j=1 upto 3:
 definecolor [name="Sea", y=(j/20), c=2*(j/10), m=(j/20)];
 yoffset := height/(j*2);
 wave[j] := (0,0)--(0,yoffset)...
 for i=1 upto stops:
   (OverlayWidth*i/(stops+1), (yoffset) randomized (height/2)) ...
 endfor
 (OverlayWidth,yoffset);
 fill ((0,0)--wave[j]--(OverlayWidth,0)--cycle) withcolor "Sea";
endfor;

xpos := OverlayWidth * RealPageNumber/NOfPages;
path ship;
ship := (0,10)---(70,10)...(60,0)---(10,0)...cycle;

pair itime, iangle, boatpos;

itime = (wave[3] intersectiontimes ((xpos,0)--(xpos,infinity)));
iangle = direction (xpart itime) of wave[3];
boatpos = (point (xpart itime) of wave[3]) shifted (-5,0); % shift to center horizontally

fill ship xysized (10,5) shifted boatpos rotatedaround (boatpos, angle iangle) withcolor red;
\stopuseMPgraph

> On 19 Jul 2023, at 12:32, Henning Hraban Ramm <texml@fiee.net> wrote:
> 
> Hi,
> I’d like a presentation progress indicator that looks like a boat on waves – and if it works, it can also become a bike on hills or a mars rover on dunes. But my math skills are lacking.
> 
> Below’s a mostly working draft.
> 
> * I find the waves not yet very convincing. Would it make sense to use a randomized sinus? (How?)
> 
> * The boat should sit on the middle wave and be rotated by the current slope. I know I need the “time” of the upper curve and get the 1st derivation, but how?
> 
> """
> \setuppapersize[SW]
> 
> \startuseMPgraphic{Waves}
> numeric height,stops,yoffset;
> stops := 10;
> height := OverlayHeight/10;
> path wave;
> 
> draw (0,0)--(OverlayWidth,0)--(OverlayWidth,OverlayHeight) withcolor white withpen pencircle scaled 0.01;
> 
> for j=1 upto 3:
>  definecolor [name="Sea", y=(j/20), c=2*(j/10), m=(j/20)];
>  yoffset := height/(j*2);
>  wave := (0,0)--(0,yoffset)...
>  for i=1 upto stops:
>    (OverlayWidth*i/(stops+1), (yoffset) randomized (height/2)) ...
>  endfor
>  (OverlayWidth,yoffset)--(OverlayWidth,0)--cycle;
>  fill wave withcolor "Sea";
> endfor;
> 
> pair pos;
> pos := (OverlayWidth * RealPageNumber/NOfPages, height/2 randomized 2);
> path ship;
> ship := (0,10)---(70,10)...(60,0)---(10,0)...cycle;
> 
> fill ship xysized (10,5) shifted pos rotatedaround (pos, 15) withcolor red;
> \stopuseMPgraphic
> 
> \defineoverlay[Waves][\useMPgraphic{Waves}]
> 
> \setupbackgrounds[state=repeat]
> \setupbackgrounds[page][background={Waves}]
> 
> \starttext
> 
> \dorecurse{10}{\recurselevel\page}
> 
> \stoptext
> """
> 
> Hraban
> ___________________________________________________________________________________
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> 
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> ___________________________________________________________________________________


— 
Taco Hoekwater              E: taco@bittext.nl
genderfluid (all pronouns)


___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / https://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : https://www.pragma-ade.nl / http://context.aanhet.net
archive  : https://bitbucket.org/phg/context-mirror/commits/
wiki     : https://contextgarden.net
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