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## Copyright (C) 2014 Philip Nienhuis
##
## This program is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program. If not, see <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} [@var{val}, @var{npts}, @var{pprt}] = clipplg (@var{val}, @var{npts}, @var{pprt}, @var{sbox}, @var{styp})
## Undocumented internal function for clipping (poly)lines within a bounding
## box and interpolating M and Z-values.
##
## @seealso{}
## @end deftypefn
## Author: Philip Nienhuis <prnienhuis@users.sf.net>
## Created: 2014-12-01
function [val, tnpt, tnpr] = clippln (val, tnpt, tnpr, sbox, styp=3)
## Backup
btnpr = tnpr;
## Prepare augmented npr array for easier indexing into subfeatures
ttnpr = [tnpr tnpt];
ctnpr = {};
## Initialize output array
valt = [];
## First step is to check all polyline vertices whether they lie in sbox
[aa, bb] = inpolygon (val(:, 1), val(:, 2), sbox(:, 1), sbox(:, 2));
if (any (aa) || any (bb))
## So there are. Morph bounding box into something that OF geometry likes:
## Parametric representation of bounding box. "createLine" is in OF geometry
ssbox = createLine (sbox(1:4, :), sbox (2:5, :));
## Create sbx from sbox ([minx max miny maxy])
sbx = [min(sbox(:, 1)), max(sbox(:, 1)), min(sbox(:, 2)), max(sbox(:, 2))];
## For those points ON the boundary no interpolation is needed.
## First treat those points requiring interpolation (1st inside,
## 2nd outside or vice versa)
for ll=1:numel (tnpr)
## Start at end of polyline-part to avoid mixing up tnpr pointers
ii = numel (tnpr) - ll + 1;
nprt = [];
## Select polyline part
valn = val(ttnpr(ii)+1:ttnpr(ii+1), :);
a = aa(ttnpr(ii)+1:ttnpr(ii+1));
if (any (a))
b = bb(ttnpr(ii)+1:ttnpr(ii+1));
da = diff (a);
idx = find (da);
## Find out which bounding box segments have been crossed where
## 1. Parametric representation of line
lines = createLine (valn(idx, 1:2), valn(idx+1, 1:2));
## 2. Compute intersections. clipLine & distancePoints are in OF geometry
for jj=1:numel (idx)
## Start at end of polyline-part to avoid mixing up tnpr pointers
kk = numel (idx) - jj + 1;
## Skip points on border
if (! b(idx(kk)+1))
intsc = reshape (clipLine (lines(kk, :), sbx), 2, 2)';
dst = distancePoints (intsc, valn(idx(kk):idx(kk)+1, 1:2));
## If segment goes out, take nearest point to valn(idx(kk)+1)
if (da(idx(kk)) < 1)
[~, ix] = min (dst(:, 2));
else
[~, ix] = min (dst(:, 1));
endif
fac = dst(ix, 2) / sum (dst(2, :));
intsc = intsc (ix, :);
## Insert new intersection point
valn(idx(kk)+2:end+1, :) = valn(idx(kk)+1:end, :);
valn(idx(kk)+1, 1:2) = intsc(1:2);
if (styp > 3)
valn(idx(kk)+1, 3:4) = valn(idx(kk)+2, 3:4) + fac * ...
(valn(idx(kk), 3:4) - valn(idx(kk)+2, 3:4));
else
valn(idx(kk)+1, 3:4) = [NaN NaN];
endif
## Also update a, b, da and idx. Also mark first point outside sbox
aa(ttnpr(ii)+idx(kk):ttnpr(ii)+idx(kk)+1) = 1;
a = [ a(1:idx(kk)); 1; a(idx(kk)+1:end) ];
b = [ b(1:idx(kk)); 1; b(idx(kk)+1:end) ];
endif
if (da(idx(kk)) < 0)
## Segment leaves bbox. Replace first outer point with NaN row
valn(idx(kk)+2, :) = NaN (1, 6);
## Be sure to include NaN row
a(idx(kk)+2) = 1;
endif
endfor
## Update valt, ttnpr
valn = valn(find(a), :);
if (! isempty (valn))
## Remove last NaN row if present
if (all (isnan (valn(end, 1:2))))
valn(end,:) = [];
endif
isn = 1;
while (! isempty (isn))
isn = find (isnan (valn(:, 1)));
if (! isempty (isn))
## Insert new subfeature pointer. npart pointers are 0-based
nprt = [ nprt isn(1) ];
valn(isn(1), :) = [];
endif
endwhile
## Build up new points from top down
valt = [ valn; valt ];
## nprt only gets non-empty if a polyline part was split up
## FIXME moet net als bij polygons
ttnpr = [ ttnpr(1:ii) (nprt+ttnpr(ii)-1) ttnpr(ii+1:end) ];
endif
endif
endfor
tnpt = size (valt, 1);
tnpr = ttnpr(1:end-1);
endif
## There's still the possibility of segments crossing through Bounding Box
## w/o having points inside. Search these segments one by one
cc = find (! aa);
if (numel (cc) > 1)
## Find discontinuities; and merge wit tnpr (multipart) discontinuities
ci = find (diff(cc) > 1)';
## Make sure to only include multipart discontinuities within range of cc
ctnpr = unique ([max(btnpr, cc(1)-1) cc(ci)' min(cc(end), size (val, 1))]);
## Create sbx from sbox ([minx max miny maxy])
sbx = [min(sbox(:, 1)), max(sbox(:, 1)), min(sbox(:, 2)), max(sbox(:, 2))];
for ic=1:numel (ctnpr) - 1
valc = val(ctnpr(ic)+1:ctnpr(ic+1), :);
## Eliminate segments that lie to one outside of the bounding box.
## Step 1: assess which side of the bounding box the segments lie
f1 = valc(:, 1) < min (sbox(:, 1));
f2 = valc(:, 1) > max (sbox(:, 1));
f3 = valc(:, 2) < min (sbox(:, 2));
f4 = valc(:, 2) > max (sbox(:, 2));
ff = [f1'; f2' ; f3' ; f4']';
## Step 2: find those segments that cross > 2 extended sbox boundary line
dd = find (sum ([abs(diff(f1)'); abs(diff(f2)'); ...
abs(diff(f3)'); abs(diff(f4)')]) > 1);
## If there are any vertices changing orientation w.r.t. bounding box:
if (! isempty (dd))
## Create array of lines potentially crossing sbox
lines = [];
for ii=1:numel (dd)
lines = [ lines; createLine(valc(dd(ii), 1:2), valc(dd(ii)+1, 1:2))];
endfor
## For each of that segment, try to compute intersections with sbox
for ii=1:numel (dd)
## clipLine is in OF geometry
jntsc = reshape (clipLine (lines, sbx), 2, 2)';
## Check if there are any intersections at all
if (! any (isnan (jntsc)))
valn = [ jntsc NaN(2, 4) ];
## Interpolate M and Z values. valc(dd(ii)+1) also required ...
dist = distancePoints (valc(dd(ii):dd(ii)+1, 1:2), valn(:, 1:2));
## ... for length of original segment:
sl = sum (dist(:, 1));
## Find closest point of original segment
valn(1, 3:4) = valc(dd(ii), 3:4) + dist(1, 1) / sl * ...
(valc(dd(ii)+1, 3:4) - valc(dd(ii), 3:4));
valn(2, 3:4) = valc(dd(ii), 3:4) + dist(1, 2) / sl * ...
(valc(dd(ii)+1, 3:4) - valc(dd(ii), 3:4));
## Adapt tnpr
tnpr = [ tnpr size(valt, 1) ];
valt = [ valt; valn ];
endif
endfor
tnpr = unique (tnpr);
endif
endfor
endif
valt(:, 5:6) = repmat (val(1, 5:6), size (valt, 1), 1);
val = valt;
endfunction
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