nrb4surf.m

强大的nurbs的工具箱 nurbs曲线

function srf = nrb4surf(p11,p12,p21,p22)
% 
% Function Name:
% 
%   nrb4surf - Constructs a NURBS bilinear surface.
% 
% Calling Sequence:
% 
%   srf = nrb4surf(p11,p12,p21,p22)
% 
% Parameters:
% 
%   p11		: Cartesian coordinate of the lhs bottom corner point.
% 
%   p12		: Cartesian coordinate of the rhs bottom corner point.
% 
%   p21		: Cartesian coordinate of the lhs top corner point.
%  
%   p22		: Cartesian coordinate of the rhs top corner point.
% 
%   srf		: NURBS bilinear surface, see nrbmak. 
% 
% Description:
% 
%   Constructs a bilinear surface defined by four coordinates.
% 
%   The position of the corner points
% 
%          ^ V direction
%          |
%          ----------------
%          |p21        p22|
%          |              |
%          |    SRF       |
%          |              |
%          |p11        p12|
%          -------------------> U direction
% 

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

if nargin < 4
  error('Four corner points must be defined'); 
end

coefs = [zeros(3,2,2); ones(1,2,2)];
coefs(1:length(p11),1,1) = p11(:);    
coefs(1:length(p12),1,2) = p12(:);
coefs(1:length(p21),2,1) = p21(:);
coefs(1:length(p22),2,2) = p22(:);
             
knots  = {[0 0 1 1] [0 0 1 1]}; 
srf = nrbmak(coefs, knots);