Code covered by the BSD License

# geom3d

### David Legland (view profile)

19 Jun 2009 (Updated )

Library to handle 3D geometric primitives: create, intersect, display, and make basic computations

### Editor's Notes:

This file was selected as MATLAB Central Pick of the Week

drawPolyhedron(nodes, faces, varargin)
function varargout = drawPolyhedron(nodes, faces, varargin)
%DRAWPOLYHEDRON Draw polyhedron defined by vertices and faces
%
%   drawPolyhedron(NODES, FACES)
%   Draws the polyhedron defined by vertices NODES and the faces FACES.
%   NODES is a NV-by-3 array containing coordinates of vertices, and FACES
%   is either a NF-by3 or NF-by-4 array containing indices of vertices of
%   the triangular or rectangular faces.
%   FACES can also be a cell array, in the content of each cell is an array
%   of indices to the nodes of the current face. Faces can have different
%   number of vertices.
%
%   H = drawPolyhedron(...);
%   Also returns a handle to the created patche.
%
%   Example:
%   [n f] = createSoccerBall;
%   drawPolyhedron(n, f);
%
%   polyhedra, drawMesh, drawPolygon
%
%   ---------
%
%   author : David Legland
%   INRA - TPV URPOI - BIA IMASTE
%   created the 10/02/2005.
%

%   HISTORY
%   07/11/2005 update doc.
%   04/01/2007 typo
%   18/01/2007 add support for 2D polyhedra ("nodes" is N-by-2 array), and
%       make 'cnodes' a list of points instead of a list of indices
%   14/09/2007 rename as drawPolyhedron
%   16/10/2008 better support for colors
%   27/07/2010 copy to 'drawMesh'

%% Initialisations

% process input arguments
switch length(varargin)
case 0
% default color is red
varargin = {'facecolor', [1 0 0]};
case 1
% use argument as color for faces
varargin = {'facecolor', varargin{1}};
otherwise
% otherwise do nothing
end

% overwrites on current figure
hold on;

% if nodes are 2D points, add a z=0 coordinate
if size(nodes, 2) == 2
nodes(1,3) = 0;
end

%% main loop : for each face

if iscell(faces)
% array FACES is a cell array
h = zeros(length(faces(:)), 1);

for f = 1:length(faces(:))
% get nodes of the cell
face = faces{f};

if sum(isnan(face))~=0
% Special processing in case of multiple polygonal face.
% each polygonal loop is separated by a NaN.

% find indices of loops breaks
inds = find(isnan(face));

% replace NaNs by index of first vertex of each polygon
face(inds(2:end))   = face(inds(1:end-1)+1);
face(inds(1))       = face(1);
face(length(face)+1)= face(inds(end)+1);
end

% draw current face
cnodes  = nodes(face, :);
h(f)    = patch(cnodes(:, 1), cnodes(:, 2), cnodes(:, 3), [1 0 0]);
end

else
% array FACES is a NC*NV indices array, with NV : number of vertices of
% each face, and NC number of faces
h = zeros(size(faces, 1), 1);
for f = 1:size(faces, 1)
% get nodes of the cell
cnodes = nodes(faces(f,:)', :);
h(f) = patch(cnodes(:, 1), cnodes(:, 2), cnodes(:, 3), [1 0 0]);
end
end

% set up drawing options
if ~isempty(varargin)
set(h, varargin{:});
end

% format output parameters
if nargout > 0
varargout = {h};
end