nrbplot.m

非均匀有理B样条的matlab程序

function nrbplot(nurbs,subd,p1,v1)
% 
% Function Name:
% 
%   nrbplot - Plot a NURBS curve or surface.
% 
% Calling Sequence:
% 
%   nrbplot(nrb,subd)
%   nrbplot(nrb,subd,p,v)
% 
% Parameters:
% 
% 
%   nrb		: NURBS curve or surface, see nrbmak.
% 
%   npnts	: Number of evaluation points, for a surface a row vector
% 		with two elements for the number of points along the U and
% 		V directions respectively.
% 
%   [p,v]       : property/value options
%
%               Valid property/value pairs include:
%
%               Property        Value/{Default}
%               -----------------------------------
%               light           {off} | true  
%               colormap        {'copper'}
%
% Example:
%
%   Plot the test surface with 20 points along the U direction
%   and 30 along the V direction
%
%   plot(nrbtestsrf, [20 30])

%  D.M. Spink
%  Copyright (c) 2000.

nargs = nargin;
if nargs < 2
  error('Need a NURBS to plot and the number of subdivisions!');
elseif rem(nargs+2,2)
  error('Param value pairs expected')
end

% Default values
light='off';
cmap='copper';

% Recover Param/Value pairs from argument list
for i=3:2:nargs
  Param = eval(['p' int2str((i-3)/2 +1)]);
  Value = eval(['v' int2str((i-3)/2 +1)]);
  if ~isstr(Param)
    error('Parameter must be a string')
  elseif size(Param,1)~=1
    error('Parameter must be a non-empty single row string.')
  end
  switch lower(Param)
  case 'light'
    light = lower(Value);
    if ~isstr(light)
      error('light must be a string.')
    elseif ~(strcmp(light,'off') | strcmp(light,'on'))
      error('light must be off | on')
    end
  case 'colormap'
    if isstr(Value)
      cmap = lower(Value);
    elseif size(Value,2) ~= 3
      error('colormap must be a string or have exactly three columns.')
    else
      cmap=Value;
    end
  otherwise
    error(['Unknown parameter: ' Param])
  end
end

colormap('default');

% convert the number of subdivisions in number of points
subd = subd+1;

% plot the curve or surface
if iscell(nurbs.knots)
  % plot a NURBS surface
  p = nrbeval(nurbs,{linspace(0.0,1.0,subd(1)) linspace(0.0,1.0,subd(2))});
  if strcmp(light,'on') 
    % light surface
    surfl(squeeze(p(1,:,:)),squeeze(p(2,:,:)),squeeze(p(3,:,:)));
    shading interp;
    colormap(cmap);
  else 
    surf(squeeze(p(1,:,:)),squeeze(p(2,:,:)),squeeze(p(3,:,:)));
    shading faceted;
  end
else
  % plot a NURBS curve
  p = nrbeval(nurbs,linspace(0.0,1.0,subd));

  if any(nurbs.coefs(3,:))
    % 3D curve
    plot3(p(1,:),p(2,:),p(3,:)); 
    grid on;
  else
    % 2D curve
    plot(p(1,:),p(2,:));
  end
end
axis equal;

% plot the control surface
% hold on;
% mesh(squeeze(pnts(1,:,:)),squeeze(pnts(2,:,:)),squeeze(pnts(3,:,:)));
% hold off;