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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{pptr}] = clipplg (@var{val}, @var{npts}, @var{pptr}, @var{sbox}[, @var{styp]})
## Undocumented internal function for clipping polygons & interpolating Z & M
## values.
##
## @seealso{}
## @end deftypefn
## Author: Philip Nienhuis <prnienhuis@users.sf.net>
## Created: 2014-11-18
## Updates:
## 2014-11-22 Create stanza for finding back vertices and interpolating Z & M
## 2014-11-25 Fix interpolating M & Z values, properly treat new corner points
## of clipped polygons
## 2014-11-26 Update tnpt and tnpr arrays
## 2015-07-10 Provision for segments crossed twice by clipping polygon
function [val, tnpt, tnpr] = clipplg (val, tnpt, tnpr, sbox, styp=5)
## Indices to start of each subfeature, plus end+1
tnprt = [(tnpr + 1) tnpt+1];
## Initialize total number of clipped vertices
tnptclp = 0;
tnprclp = cell (numel (tnpr, 1));
for kk=1:numel (tnpr)
## Work from end back to start of subfeatures to avoid mixing up index arrays
jj = numel (tnpr) - kk + 1;
## Select rows belonging to this partial feature. First save non-selected rows
b_val = e_val = [];
if (jj > 1)
## There's one or more subfeatures lower down
b_val = val(1:tnprt(jj)-1, :);
endif
if (jj < numel (tnpr))
## There's one or more subfeatures higher up
e_val = val(tnprt(jj+1):end, :);
endif
tval = val(tnprt(jj):tnprt(jj+1)-1, :);
## oc_polybool is in OF geometry package
[X, Y, npol, b, c] = oc_polybool (tval(:, 1:2), sbox, 'AND');
## Initialize new number of points & new part pointers in clipped polygon(s)
nptclp = 0;
nprclp = 0;
valn = [];
if (npol)
## Make an XY matrix, remove NaNs on upper and lower row
valc = [X Y](2:end-1, :);
## Augment NaNs for Z and M, and augment type + shape record index columns
ncl = size (valc, 1);
valc = [ valc NaN(ncl, 2) tval(1, 5)*ones(ncl, 1) tval(1, 6)*ones(ncl, 1) ];
## Pointers to subpolygons resulting from clipping
ipt = find (isnan (valc(:, 1)))';
ipt = [ 0 ipt (size (valc, 1) + 1) ];
## For each new polygon...
for ipol=1:npol
valn = valc(ipt(ipol)+1:ipt(ipol+1)-1, :);
## Update total number of points in clipped polygon(s)
nptclp += size (valn, 1);
tnptclp += size (valn, 1);
## Add a new 0-based pointer to next part
nprclp = [ nprclp nptclp ];
## Compute all interdistances. distancePoints is in OF geometry package
## Avoid polygon end point ( = start point)
dsts = distancePoints (valn(1:end-1, 1:2), tval(1:end-1, 1:2));
## Find matching points in sub and out polygon (row, col)
[rw, cl] = ind2sub (size (dsts), find (abs (dsts) < eps));
## Transfer known Z and M-values
valn(rw, 3:4) = tval(cl, 3:4);
## cl indices refer to original shape, rw indices to clipped shape
if (numel (cl) >= 1)
## Separate polygon segments clipped, or vertex on bounding box side
## For each valn row coords not in tval, interpolate Z and M values
im = setdiff ([1:size(valn, 1)-1], rw);
## mi equals cl filled with zeros for non-matches, to easen indexing
mi = zeros (1, size (valn, 1) - 1);
mi(rw) = cl;
## Find direction of polyline
pdir = find (abs (diff (rw)) - 1 < eps);
if (isempty (pdir))
## Single point within bounding box. Direction doesn't matter then
drctn = 1;
else
drctn = sign (diff (rw([pdir pdir+1])))(1);
endif
for ii=1:numel (im)
## Get matching outer vertex. Below IF-ELSEIF order = critical to
## avoid index out-of-range errors
if (im(ii) == 1)
## Clipped off outer vertex = previous in tval. diff(cl) = direction
intpl = true;
idx = mi(im(ii)+1) - drctn;
ovtx = tval(idx, :);
cvtx = tval(mi(im(ii)+1), :);
elseif ((! ismember (im(ii)-1, rw)) && (! ismember (im(ii)+1, rw)))
## Probably a corner point. Just retain NaN values
intpl = false;
elseif (! ismember (im(ii)-1, rw))
## Clipped off outer vertex = previous in tval. diff(cl) = direction
intpl = true;
idx = mi(im(ii)+1) - drctn;
ovtx = tval(idx, :);
cvtx = tval(mi(im(ii)+1), :);
elseif (! ismember (im(ii)+1, rw))
## Clipped off outer vertex = next in tval. diff(cl) = direction
intpl = true;
idx = mi(im(ii)-1) + drctn;
ovtx = tval(idx, :);
cvtx = tval(mi(im(ii)-1), :);
endif
## Parent points found, now interpolate M and Z (if appropriate)
if (intpl && styp > 5)
## Compute missing M and Z values. Invoke largest diff of X/Y coordinates
difx = abs (cvtx(1) - ovtx(1));
dify = abs (cvtx(2) - ovtx(2));
if (difx > dify)
## X distance is greater
fac = (valn(im(ii), 1) - cvtx(1)) / difx;
else
## Y distance is greater
fac = (valn(im(ii), 2) - cvtx(2)) / dify;
endif
fac = abs(fac);
## FIXME a debug stmt to detect wrong interpolation => wrong vertices
if (fac > 1.0)
printf ("Oops - fac > 1..\n");
% keyboard
endif
if (isfinite (ovtx(3)))
valn(im(ii), 3) = fac * (ovtx(3) - cvtx(3)) + cvtx(3); ## Z-value
endif
if (isfinite (ovtx(4)))
valn(im(ii), 4) = fac * (ovtx(4) - cvtx(4)) + cvtx(4); ## M-value
endif
endif
endfor
## Remove last nprclp entry and temporarily store it in a cell arr
tnprclp(jj) = nprclp;
elseif (numel (cl) == 0)
## One polygon segment clipped twice. Simply assign nearest Z & M values
## FIXME proper interpolation required
## Find points interpolated on segment(s); they're not in sbox
[im, ix] = min (distancePoints (sbox(1:end-1, :), valn(1:end-1, 1:2)));
im = find (im > 0);
ix = ix(im);
## Find nearest polygon points (could be on another polygon segment !)
[~, ix] = min (distancePoints (tval(1:end-1, 1:2), valn(im, 1:2)));
## Assign Z and M values
valn(im, 3:4) = tval(ix, 3:4);
## Remove last nprclp entry and temporarily store it in a cell arr
tnprclp(jj) = nprclp;
endif
## Last row of polygon equals first
valn(end, :) = valn(1, :);
## Augment new polygon after (yet untouched) previous polygons
b_val = [ b_val; valn ];
endfor ## clipped subpolygons
else
## No intersection at all. Just drop tval
% tnprclp = {};
endif
val = [b_val ; e_val];
tnprt(jj+1:end) -= tnprt(jj+1) - tnprt(jj) - size (valn, 1);
if (isempty (valn))
## This subfeature has no points in boundingbox +> drop from list
tnprt(jj+1) = [];
endif
endfor
## Adapt & clean up npt
tnpt = tnptclp;
## Adapt & clean up npr. Concatenate all pointers created by oc_polybool
tnpr = [ tnprclp{1} ];
for ii=2:numel (tnprclp)
## Skip empty entries
if (! isempty (tnprclp{ii}))
tnpr = [tnpr(1:end-1) (tnprclp{ii} + tnpr(end)) ];
endif
endfor
if (! isempty (tnpr))
tnpr(end) = [];
endif
endfunction
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