% Create the object's surface<BR>
function MakeSurface(sX,sY,pX,pY,size,edgeflag,styleflag,alt,azm,res);
<P>
cla;
<P>
% Lighting<BR>
kd = .7 ;			% Diffuse<BR>
ka = .1 ;			% Ambient<BR>
ks = .7 ; ns = 10 ;	% Specular
<P>
% Set up edges vs shading<BR>
if edgeflag == 1<BR>
   Edgemode = 'black' ;<BR>
   Lmode = 'none' ;<BR>
else<BR>
   Edgemode = 'none' ;<BR>
   Lmode = 'phong' ;<BR>
end
<P>
% Set up surface variables<BR>
n = length(pX);<BR>
xMat = zeros(n,n);<BR>
yMat = zeros(n,n);<BR>
zMat = zeros(n,n);
<P>
% Create the surface by scaling<BR>
if styleflag == 1<BR>
   xMat = pX' * sX;<BR>
   yMat = pY' * sX;<BR>
   zMat = ones(n,1) * sY;
<P>
% Create the surface by rotation<BR>
else<BR>
   for i = 1:n<BR>
      % Calculate the components of slope<BR>
      if (i == 1)<BR>
         dx = pX(2) - pX(1);<BR>
         dy = pY(2) - pY(1);<BR>
      elseif (i == n)<BR>
         dx = pX(n) - pX(n-1);<BR>
         dy = pY(n) - pY(n-1);<BR>
      else<BR>
         dx = pX(i+1) - pX(i-1);<BR>
         dy = pY(i+1) - pY(i-1);<BR>
      end
<P>
      % Specify rotation angle theta<BR>
      if (dx == 0)<BR>
         if (dy > 0)<BR>
            theta = pi/2;<BR>
         else<BR>
            theta = 3*pi/2;<BR>
         end<BR>
      else<BR>
         theta = atan(dy/dx);<BR>
         if (dx < 0)<BR>
            theta = theta + pi;<BR>
         end<BR>
      end
<P>
      % Create a single cross-section<BR>
      xMat(i,:) = -sX * sin(theta) + pX(i);<BR>
      yMat(i,:) = sX * cos(theta) + pY(i);<BR>
      zMat(i,:) = sY;<BR>
   end
<P>
   % If the path is closed, overlap the edges to ensure their connection<BR>
   if (pX(1) > pX(n)-0.01) & (pX(1) < pX(n)+0.01) & (pY(1) > pY(n)-0.01) & (pY(1) < pY(n)+0.01)<BR>
      xMat = [xMat;xMat(1,:)];<BR>
      yMat = [yMat;yMat(1,:)];<BR>
      zMat = [zMat;zMat(1,:)];<BR>
   end<BR>
end
<P>
% Plot the surface<BR>
hndl = surfl(xMat,yMat,zMat);
<P>
% Specify surface characteristics<BR>
set(hndl,'EdgeColor',Edgemode);<BR>
set(hndl,'FaceColor',[1,.6,.4]);<BR>
set(hndl,'FaceLighting',Lmode);<BR>
set(hndl,'DiffuseStrength',kd);<BR>
set(hndl,'AmbientStrength',ka);<BR>
set(hndl,'SpecularStrength',ks);<BR>
set(hndl,'SpecularExponent',ns);
<P>
% Specify view parameters<BR>
view(azm, alt) ;<BR>
light ('position', [1, 1 ,0] )
<P>
% Set axes<BR>
axis([-size size -size size -size size])