mk_tri_2dfc.m

function [tri,xy,nt] = mk_tri_2dfc(dat,clip,dist,tol,iplt)
%MK_TRI_2DF Makes a triangular mesh by using boundary line data from
%        a two-dimensional digitized MRI slice.  The first line is
%        assumed to be cartilage and the second line is assumed to
%        be bone.
%
%        [TRI,XY] = MK_TRI_2DF(DAT,CLIP) given a cell array containing
%        two (2) columns matrices with boundary line coordinate point
%        data, DAT, and a two elements logical array which is true if
%        the ends of the bone line need to be clipped, CLIP, returns a
%        three (3) column triangle connectivity matrix, TRI, and X and
%        Y coordinates in a two columns matrices XY.
%
%        [TRI,XY,NT] = MK_TRI_2DF(DAT,CLIP) returns the number of
%        triangles, NT.
%
%        [TRI,XY] = MK_TRI_2DF(DAT,CLIP,DIST) given a distance, DIST,
%        ensures truncated endpoints on the second boundary line are
%        within two DIST distances of the first boundary line endpoints.
%
%        NOTES:  1.  Each boundary coordinate data matrix must
%                correspond to one index into the cell array DAT.
%
%                2.  The coordinates should be ordered in the same
%                direction in each line.  The dot product of the
%                directions of the adjacent lines are used to check the
%                ordering direction and the ordering direction is
%                reversed if the dot product is negative.
%
%                3.  The second boundary line may be truncated if it
%                extends pass the first boundary line if CLIP is true
%                for either end of the line.
%
%                4.   M-files lsect2a.m and near2.m must be in the
%                current directory or path.
%
%                5.  Similar to mk_tri_2dc.m except the slopes of the
%                end points are in the opposite directions.
%
%        07-Feb-2023 * Mack Gardner-Morse
%

%#######################################################################
%
% Check for Inputs
%
if (nargin<2)
  error(' *** ERROR in mk_tri_2dfc:  Two inputs are required!');
end
%
clip = clip(:);
%
if nargin<3||isempty(dist)
  dist = Inf;            % No distance checking
end
%
diste = 2*dist;         % Distance from cartilage end points to line of bone points
diste = diste*diste;    % Squared distance for comparison to squared lengths
%
if nargin<4||isempty(tol)
  tol = 0.1;
end
%
if nargin<5
  iplt = false;
end
%
dat = dat(:);
nslice = size(dat,1);
%
if nslice~=2
  error([' *** ERROR in mk_tri_2dfc:  Input cell array must ', ...
         'have two elements containing 2D coordinates for two lines!']);
end
%
% Get First (Cartilage) Line and Slopes at the Ends of the Line
%
xy1 = dat{1};
npts1 = size(xy1,1);
%
vec1 = xy1(npts1,:)-xy1(1,:);          % Direction of line
vec1 = vec1./norm(vec1);
%
dd = diff(xy1);
de = dd([1,npts1-1],:);                % Slopes at ends of top line
%
% Ends of First (Cartilage) Line
%
mp = -de(:,1)./de(:,2); % 90 degrees
ids = abs(de(:,2))<1e-8;
mp(ids) = sign(mp(ids))*1e+4;          % Large but not infinite slope
% mp(2,1) = (de(2,1)-de(2,2))./(de(2,1)+de(2,2));  % 45 degrees
% mp(1,1) = (de(1,2)+de(1,1))./(de(1,1)-de(1,2));  % 45 degrees
% ratio = tan(pi/3);      % Opposite to adjacent for 60 degrees (pi/3 radians)
% mp(2,1) = (de(2,2)+ratio*de(2,1))./(de(2,1)-ratio*de(2,2));     % 60 degrees
% mp(1,1) = (ratio*de(1,2)-de(1,1))./(de(1,1)+ratio*de(1,2));     % 60 degrees
xp = xy1([1; npts1],1);
yp = xy1([1; npts1],2);
bp = yp-mp.*xp;
%
% Get Second (Bone) Line
%
xy2 = dat{2};
npts2 = size(xy2,1);
%
vec2 = xy2(npts2,:)-xy2(1,:);
vec2 = vec2./norm(vec2);
%
% Check for Slices with a Reverse Digitization
%
dotp = vec1*vec2';
%
if dotp<tol
  xy2 = flipud(xy2);
  clip = flipud(clip);
  vec = xy2(npts2,:)-xy2(1,:);
  vec = vec./norm(vec);
  dotp2 = vec1*vec';
  if dotp2<dotp         % Revert back to original ordering
    warning([' *** WARNING in mk_tri_2df:  Ordering of points', ...
             ' in the slices may not be in the same direction!']);
    xy2 = flipud(xy2);
    clip = flipud(clip);
  end
end
%
% Cut Off Extra Points on Second (Bone) Line
% Fails if Second (Bone) is Not Longer Than First (Cartilage) Line
%
id1 = 1;
itrap1 = false;
if clip(1)
  [xyi,id1] = lsect2a(mp(1),bp(1),xy2);     % Get all intersections
  ni = size(id1,1);
  if ni>1
    idp = near2([xp(1) yp(1)],xyi);    % Get nearest point
    id1 = id1(idp);
    xyi = xyi(idp,:);
  end
  d = xyi-xy1(1,:);
  d = d*d';
  if d>diste            % Bone line within 2 DIST of cartilage end points
    id1 = 1;
  end
  if isempty(id1)
    itrap1 = true;
    id1sav = npts2-1;
    xy3 = xy2;
    id1 = 1;
  end
  if id1>npts2/1.5      % Intersection at other end of femoral bone?
    itrap1 = true;
    id1sav = id1;
    xy3 = xy2;
    id1 = 1;
  end
end
%
id2 = npts2-1;
itrap2 = false;
if clip(2)
  [xyi,id2] = lsect2a(mp(2),bp(2),xy2);     % Get all intersections
  ni = size(id2,1);
  if ni>1
    idp = near2([xp(2) yp(2)],xyi);    % Get nearest point
    id2 = id2(idp);
    xyi = xyi(idp,:);
  end
  d = xyi-xy1(npts1,:);
  d = d*d';
  if d>diste            % Bone line within 2 DIST of cartilage end points
    id2 = npts2-1;
  end
  if isempty(id2)
    itrap2 = true;
    id2sav = 1;
    xy3 = xy2;
    id2 = npts2-1;
  end
  if id2<npts2-npts2/1.5     % Intersection at other end of femoral bone?
    itrap2 = true;
    id2sav = id2;
    xy3 = xy2;
    id2 = npts2-1;
  end
end
%
idc = id1:id2+1;
nptc = length(idc);
xy2 = xy2(idc,:);
xy = [xy1; xy2];
%
% Delaunay Triangulation
%
n = [0; cumsum([npts1; nptc])];
%
c1 = [(n(1)+1:n(2)-1)' (n(1)+2:n(2))'; n(2) n(3); (n(3):-1:n(2)+2)' ...
      (n(3)-1:-1:n(2)+1)'; n(2)+1 n(1)+1];       % Constraints
%
dt1 = delaunayTriangulation(xy,c1);    % Delaunay Triangulation
%
[~,id] = lastwarn;
if contains(id,'delaunay','IgnoreCase',true)&&(itrap1||itrap2)
  if itrap1
    id1 = id1sav;
    xy2 = xy3;
  end
  if itrap2
    id2 = id2sav;
    xy2 = xy3;
  end
%
  idc = id1:id2+1;
  nptc = length(idc);
  xy2 = xy2(idc,:);
  xy = [xy1; xy2];
%
  n = [0; cumsum([npts1; nptc])];
%
  c1 = [(n(1)+1:n(2)-1)' (n(1)+2:n(2))'; n(2) n(3); (n(3):-1:n(2)+2)' ...
        (n(3)-1:-1:n(2)+1)'; n(2)+1 n(1)+1];       % Constraints
%
  dt1 = delaunayTriangulation(xy,c1);     % Delaunay Triangulation
%
  lastwarn('');
end  
%
idin = isInterior(dt1);
tri = dt1(idin,:);
nt = size(tri,1);
%
% Plot Triangulations?
%
if iplt
%
  h1 = figure;
  orient tall;
%
  xt = xy(:,1);
  yt = xy(:,2);
%
  plot(xt,yt,'k.','LineWidth',1,'MarkerSize',7);
  hold on;
  npts = size(xt,1);
  text(xt,yt,int2str((1:npts)'),'Color','k','FontSize',10);
%
  trimesh(tri,xt,yt);
  text(mean(xt(tri),2),mean(yt(tri),2),int2str((1:nt)'), ...
       'Color','r','FontSize',10);
%
  h2 = figure;
  orient tall;
  plot(xy2(:,1),xy2(:,2),'k.-','LineWidth',1,'MarkerSize',7);
  hold on;
  plot(xy1(:,1),xy1(:,2),'b.-','LineWidth',1,'MarkerSize',7);
  text(xt,yt,int2str((1:npts)'),'Color','k', ...
       'FontSize',10);
%
  xp = reshape(xy(tri,1),nt,3)';
  yp = reshape(xy(tri,2),nt,3)';
  xp = repmat(mean(xp),3,1)+0.75*(xp-repmat(mean(xp),3,1));
  yp = repmat(mean(yp),3,1)+0.75*(yp-repmat(mean(yp),3,1));
  patch(xp,yp,[1 0.7 0.7]);
  text(mean(xt(tri),2),mean(yt(tri),2),int2str((1:nt)'), ...
       'Color','r','FontSize',10);
%
  axis equal;
  pause;
  close(h1,h2);
%
end
%
return