B-spline: Difference between revisions

* [https://www.cl.cam.ac.uk/teaching/2000/AGraphHCI/SMEG/node4.html B-splines]

<br><br>

=={{header|ALGOL 68}}==

{{Trans|Lua}}Which is {{Trans|Wren}}Suppresses unused parts of the plot.

 

# mode to hold a B Spline #

[ lb : ub ]INT range;

FOR n FROM lb TO ub DO range[ n ] := n OD;

END # uniform knot vector # ;

 

PROC calculate bspline = ( REF BSPLINE bs, INT i, k, x )REAL:

THEN ABS ( ( t OF bs )[ i ] <= x AND x < ( t OF bs )[ i + 1 ] )

PROC helper = ( REF BSPLINE bs, INT i, k, x )REAL:

IF ( t OF bs )[ i + k ] /= ( t OF bs )[ i ]

REAL sum x := 0;

REAL sum y := 0;

REAL f = calculate bspline( bs, i, k OF bs, x );

sum x +:= f * ( control points OF bs )[ i, 1 ];

sum y +:= f * ( control points OF bs )[ i, 2 ]

OD;

points[ x, 2 ] := round( sum y )

OD;

INT x := x0;

INT y := y0;

INT dy := ABS ( y2 - y );

INT dir y = IF y2 > y THEN 1 ELSE -1 FI;

dx *:= 2;

dy *:= 2;

 

PROC plot line = ( REF[,]BOOL plot, INT x1, y1, x2, y2 )VOID:

, ( REF[,]BOOL plot, INT x, INT y )VOID: IF x >= 0

AND y >= 0

AND y < 2 UPB plot

THEN plot[ x + 1, y + 1 ] := TRUE

);

 

PROC plot bspline = ( REF BSPLINE bs, REF[,]BOOL plot, REAL scale x, scale y )VOID:

IF k OF bs > n OF bs OR k OF bs < 1 THEN

stop

ELSE

)

OD

 

# print the plot - outputs @ or blank depending on whether the point is plotted or not #

);

INT k = 4; # Polynomial degree is one less than this i.e. cubic. #

, UPB control points

, k

plot bspline( bs, plot, scale x, scale y );

print plot( plot )

{{out}}

leading blank lines removed...

<pre>

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=={{header|Julia}}==

Choose BSpline D of 2, ie degree 1.

 

Point(t::Tuple) = Vec2(Float64(t[1]), Float64(t[2]))

plt = plot(map(a -> a.x, controlpoints), map(a -> a.y, controlpoints))

savefig(plt, "BSplineplot.png")</syntaxhighlight>

=={{header|Lua}}==

 

{{trans|Wren}}

 

local range = {}

for n = from, to do table.insert(range, n) end

@@@

</pre>

=={{header|Mathematica}}/{{header|Wolfram Language}}==

BSplineCurve[{{171, 171}, {185, 111}, {202, 109}, {202, 189}, {328,

160}, {208, 254}, {241, 330}, {164, 252}, {69, 278}, {139,

{{out}}

Outputs a graphical representation of a B-spline.

=={{header|Perl}}==

{{trans|Raku}}

use warnings;

use Class::Struct;

$surf->write_to_png($OUTPUT);</syntaxhighlight>

Output: [https://raw.githubusercontent.com/SqrtNegInf/Rosettacode-Perl-Smoke/master/ref/b-spline.png b-spline.png] (offsite image)

=={{header|Phix}}==

{{trans|Wren}}

{{libheader|Phix/online}}

You can run this online [http://phix.x10.mx/p2js/bspline.htm here].

<span style="color: #000080;font-style:italic;">--

-- demo\rosetta\B-spline.exw

<span style="color: #000000;">main</span><span style="color: #0000FF;">()</span>

<!--</syntaxhighlight>-->

=={{header|Processing}}==

//Aamrun, 26th June 2022

 

 

</syntaxhighlight>

=={{header|Raku}}==

A minimal translation of [https://www.cypherpunk.at/download/bspline/bspline_1.1.tbz2 this C program], by [https://github.com/rahra Bernhard R. Fischer].

 

use Cairo;

 

Output: [https://drive.google.com/file/d/1dInRJeecA18meybDF2D0usEaWMGFqoBj/view (Offsite image file) ]

=={{header|Wren}}==

{{libheader|DOME}}

 

If one uses a value for k of 1, then the script will simply plot the control points as in the Julia example.

import "graphics" for Canvas, Color