z value is missing during using surf for plotting

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jarvan
jarvan 2014-12-14
评论： Star Strider 2014-12-14
I have a user-program which is download on http://tinyurl.com/p4uqz4r. I have to use surf to plot a right circular cone with base R=1at r1= [0, 0, 0] and apex R=0 at r2=[1, 1, 1]. However, when I put R=0,r1= [0, 0, 0],r2=[1, 1, 1] the surf function cant go through because I dont have a z value. I don't have how can I plot with surf with above requirment, which is R=1at r1= [0, 0, 0] and apex R=0 at r2=[1, 1, 1].
function [X, Y, Z] = cylinder2P(R, N,r1,r2)
% The parametric surface will consist of a series of N-sided
% polygons with successive radii given by the array R. Axial
% distance Z increases in equal sized steps from 0 to 1 along
% the line lying between points r1 and r2.
% Author: Luigi Barone
% Date: 9 September 2001
% Modified: Per Sundqvist July 2004
% Set up an array of angles for the polygon.
theta = linspace(0,2*pi,N);
m = length(R); % Number of radius values
% supplied.
if m == 1 % Only one radius value supplied.
R = [R; R]; % Add a duplicate radius to make
m = 2; % a cylinder.
end
X = zeros(m, N); % Preallocate memory.
Y = zeros(m, N);
Z = zeros(m, N);
v=(r2-r1)/sqrt((r2-r1)*(r2-r1)'); %Normalized vector;
%cylinder axis described by: r(t)=r1+v*t for 0<t<1
R2=rand(1,3); %linear independent vector (of v)
x2=v-R2/(R2*v'); %orthogonal vector to v
x2=x2/sqrt(x2*x2'); %orthonormal vector to v
x3=cross(v,x2); %vector orthonormal to v and x2
x3=x3/sqrt(x3*x3');
r1x=r1(1);r1y=r1(2);r1z=r1(3);
r2x=r2(1);r2y=r2(2);r2z=r2(3);
vx=v(1);vy=v(2);vz=v(3);
x2x=x2(1);x2y=x2(2);x2z=x2(3);
x3x=x3(1);x3y=x3(2);x3z=x3(3);
time=linspace(0,1,m);
for j = 1 : m
t=time(j);
X(j, :) = r1x+(r2x-r1x)*t+R(j)*cos(theta)*x2x+R(j)*sin(theta)*x3x;
Y(j, :) = r1y+(r2y-r1y)*t+R(j)*cos(theta)*x2y+R(j)*sin(theta)*x3y;
Z(j, :) = r1z+(r2z-r1z)*t+R(j)*cos(theta)*x2z+R(j)*sin(theta)*x3z;
end
%surf(X, Y, Z);

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采纳的回答

Star Strider
Star Strider 2014-12-14
You can do that with the built-in cylinder function, using its ability to create shapes from cylinders:
q = 0:0.1:1;
[X,Y,Z] = cylinder(q);
figure(1)
surf(X,Y,Z)
Experiment with it to get the result you want.
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Star Strider
Star Strider 2014-12-14
My pleasure!
The cylinder2P function looks useful. I suppose it would be possible to do much the same thing with cylinder and rotate, similar to this archive ‘spilled bottle’ code:
f = @(x) x.*exp(-x);
x = linspace(0, 5, 31);
[X, Y, Z] = cylinder(f(x));
figure(1)
h = surf(X, Y, Z)
rotate(h, [0 1 0], 90)
xlabel('X')
ylabel('Y')
zlabel('Z')
axis equal

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