Changing from 2D plot to 3D plot and to STL file

Hello everyone, I have these following codes: All of them creates a 2D plot, now I really want to create a 3D plot with Z: the thickness of plot XY. Then I want to convert it to STL file.

clc;
clear all;
close all;
% Input
R0 = 0.15;
a = 25*pi/180;
theta = 0:pi/1000:3*pi;
theta2 = theta + pi;
delta = pi/2;
%% Curl 1
R1 = R0*exp(a*(theta-delta));
X1 = R1.*cos(theta-delta);
Y1 = R1.*sin(theta-delta);
%% Curl 2
R2 = R0*exp(a*(theta-delta));
X2 = R2.*cos(theta);
Y2 = R2.*sin(theta);
%% Curl 3
R3 = R0*exp(a*(theta2-delta));
X3 = R1.*cos(theta2-delta);
Y3 = R1.*sin(theta2-delta);
%% Curl 4
R4 = R0*exp(a*(theta2 - delta));
X4 = R2.*cos(theta2);
Y4 = R2.*sin(theta2);
%% Extra plot (arc)
radius = R0*exp(a*(3*pi-pi/2));
a1 = pi/2;
b1 = pi;
h = 0;
k = 0;
t1 = linspace(a1,b1,3001);
X_arc1 = radius*cos(t1) + h;
Y_arc1 = radius*sin(t1) + k;

a2 = -pi/2;
b2 = 0;
t2 = linspace(a2,b2,3001);
X_arc2 = radius*cos(t2) + h;
Y_arc2 = radius*sin(t2) + k;

R5 = 0.05;
X5 = R5.*cos(theta);
Y5 = R5.*sin(theta);
%% Plot
figure(1);
plot(X1,Y1, 'k', 'LineWidth', 3); hold on
plot(X2,Y2, 'k', 'LineWidth', 3); hold on

P1 = plot(X_arc1, Y_arc1, 'k');
set(P1,'linewidth',3);
axis([h-radius-1 h+radius+1 k-radius-1 k+radius+1]) 
axis square; hold on;

plot(X3,Y3, 'k', 'LineWidth', 3);hold on
plot(X4,Y4, 'k', 'LineWidth', 3);hold on
plot(X5,Y5, 'k', 'LineWidth', 3); hold on

P2 = plot(X_arc2, Y_arc2, 'k');
set(P2,'linewidth',3);
axis('equal');
title('Two-arm equiangular spiral antenna', 'fontsize',14, 'fontweight','bold');
hold on
%% Filling with black color
patch([X1; flipud(X2)], [Y1; flipud(Y2)],'k');
patch([X3; flipud(X4)], [Y3; flipud(Y4)],'k');

X_arc1_bonus = horzcat(X_arc1, -4, -2.2, -2, -1, -0.3);
Y_arc1_bonus = horzcat(Y_arc1, 0.8, 2.2, 2.6, 3, 3.2);
fill(X_arc1_bonus, Y_arc1_bonus,'k');

X_arc2_bonus = horzcat(X_arc2, 4, 2.2, 2, 1, 0.3);
Y_arc2_bonus = horzcat(Y_arc2, -0.8, -2.2, -2.6, -3, -3.2);
fill(X_arc2_bonus, Y_arc2_bonus,'k');

Answer 1

[Deepak]

Hi @Anh Phan Viet,

To create a 3D plot with thickness by extruding 2D shapes into the third dimension, we can use "fill3" function in MATLAB.

Initially, the 2D shapes are defined by their X and Y coordinates. These shapes are then duplicated along the Z-axis to form both the bottom (Z = 0) and top (Z = thickness) surfaces, effectively giving them volume. The "fill3" function is used to plot these surfaces by specifying the X, Y, and Z coordinates for each shape. To complete the 3D model, side walls are created by connecting corresponding points on the top and bottom surfaces, forming vertical quadrilateral patches. This process results in a solid 3D object with defined thickness, visualized in a 3D space using plotting capabilities of MATLAB.

Below is a sample MATLAB to achieve the same:

% Input parameters
R0 = 0.15;
a = 25*pi/180;
theta = 0:pi/1000:3*pi;
theta2 = theta + pi;
delta = pi/2;
thickness = 0.05; % Thickness for the 3D extrusion

% Curl 1
R1 = R0*exp(a*(theta-delta));
X1 = R1.*cos(theta-delta);
Y1 = R1.*sin(theta-delta);

% Curl 2
R2 = R0*exp(a*(theta-delta));
X2 = R2.*cos(theta);
Y2 = R2.*sin(theta);

% Curl 3
R3 = R0*exp(a*(theta2-delta));
X3 = R1.*cos(theta2-delta);
Y3 = R1.*sin(theta2-delta);

% Curl 4
R4 = R0*exp(a*(theta2 - delta));
X4 = R2.*cos(theta2);
Y4 = R2.*sin(theta2);

% Extra plot (arc)
radius = R0*exp(a*(3*pi-pi/2));
a1 = pi/2;
b1 = pi;
h = 0;
k = 0;
t1 = linspace(a1,b1,3001);
X_arc1 = radius*cos(t1) + h;
Y_arc1 = radius*sin(t1) + k;
a2 = -pi/2;
b2 = 0;
t2 = linspace(a2,b2,3001);
X_arc2 = radius*cos(t2) + h;
Y_arc2 = radius*sin(t2) + k;

% Create a 3D plot with thickness
figure;
hold on;

% Extrude each 2D shape into 3D
fill3([X1; flipud(X2)], [Y1; flipud(Y2)], zeros(size([X1; flipud(X2)])), 'k');
fill3([X1; flipud(X2)], [Y1; flipud(Y2)], thickness * ones(size([X1; flipud(X2)])), 'k');
fill3([X3; flipud(X4)], [Y3; flipud(Y4)], zeros(size([X3; flipud(X4)])), 'k');
fill3([X3; flipud(X4)], [Y3; flipud(Y4)], thickness * ones(size([X3; flipud(X4)])), 'k');

% Extrude arcs
fill3(X_arc1, Y_arc1, zeros(size(X_arc1)), 'k');
fill3(X_arc1, Y_arc1, thickness * ones(size(X_arc1)), 'k');
fill3(X_arc2, Y_arc2, zeros(size(X_arc2)), 'k');
fill3(X_arc2, Y_arc2, thickness * ones(size(X_arc2)), 'k');

% Connect top and bottom faces to create side walls
for i = 1:length(X1)-1
    fill3([X1(i), X1(i+1), X1(i+1), X1(i)], [Y1(i), Y1(i+1), Y1(i+1), Y1(i)], [0, 0, thickness, thickness], 'k');
end

% Repeat similarly for other parts...
axis equal;
view(3);
title('3D Model of Two-arm Equiangular Spiral Antenna');

Please find attached documentation of funcitons used for reference:

fill3: www.mathworks.com/help/matlab/ref/fill3.html

array indexing: www.mathworks.com/help/matlab/math/array-indexing.html

I hope this helps in resolving the issue.