How to create a random 3d point cloud

Hello

I would like to create a random 3D pointcloud (in the pointcloud format) and then fit a 3D curve (spline) passing through it (randomly).

How is it possible ?

Please help me.

Thank You.

[Andreas Dorner]

Probably not what you want, but random:

size = 10;
nPoints = 1000;
vars = rand(nPoints, 3)*size;
pc = pointCloud(vars)

[julio cruz]

Is there a way to create a random 3D point cloud but have it be within some other point cloud that has the shape of a cube?

[darova]

Can you make a sketch or drawing?

[julio cruz]

Attached is the cuboid created in matlab and the data points used. Also, here is the code i used:

dataset = xlsread('data.xlsx','Sheet1','a1:c25');

x = dataset(:,1);
y = dataset(:,2);
z = dataset(:,3);
t=[x y z];
ptCloud = pointCloud(t);
pcshow(ptCloud)

[darova]

I draw your data

So you want to draw random 3D curve. What happens if the curve hits the boundaries of this 'cube'?

[julio cruz]

the curve cannot go past the boundaries of the cube

[darova]

I think it's too complicated

If it was a 2D dimensional case i'd just use inpolygon to check if curve is inside the box. But it's 3D

I can't handle it

Do you have any ideas?

[Image Analyst]

Surprised no one is trying spline(). ?

Answer 1

[Image Analyst]

Try using spline() on each of x, y, and z separately:

% Initialization steps.
clc;    % Clear the command window.
fprintf('Beginning to run %s.m ...\n', mfilename);
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 15;

data = xlsread('data.xlsx')
x = data(:, 1);
y = data(:, 2);
z = data(:, 3);
hFig1 = figure;
plot3(x, y, z, 'b.-', 'MarkerSize', 20, 'LineWidth', 2);
xlabel('x', 'FontSize', fontSize);
ylabel('y', 'FontSize', fontSize);
zlabel('z', 'FontSize', fontSize);
grid on;
hFig1.WindowState = 'maximized';

% Now spline fit 1000 points in between.
hFig2 = figure;
xq = linspace(1, length(x), 1000);
xs = spline(1:length(x), x, xq);
yq = linspace(1, length(y), 1000);
ys = spline(1:length(y), y, yq);
zq = linspace(1, length(z), 1000);
zs = spline(1:length(z), z, zq);
% Plot them.
subplot(2, 1, 1);
plot(1 : length(x), x, 'r.', 'MarkerSize', 20);
hold on;
plot(1 : length(y), y, 'g.', 'MarkerSize', 20);
plot(1 : length(z), z, 'b.', 'MarkerSize', 20);
title('Original X, Y, and Z Values', 'FontSize', fontSize);
legend('x', 'y', 'z');

subplot(2, 1, 2);
plot(1 : length(xs), xs, 'r-', 'LineWidth', 2);
hold on;
plot(1 : length(ys), ys, 'g-', 'LineWidth', 2);
plot(1 : length(zs), zs, 'b-', 'LineWidth', 2);
grid on;
title('Spline Fits', 'FontSize', fontSize);
legend('x', 'y', 'z');

% Plot back on the main figure in red.
figure(hFig1);
hold on;
plot3(xs, ys, zs, 'r-', 'LineWidth', 2);

% Clip all values to no lower than 0.
xs = max(0, xs);
ys = max(0, ys);
zs = max(0, zs);
% Clip all values to no higher than 1.
xs = min(1, xs);
ys = min(1, ys);
zs = min(1, zs);
% Plot clipped range back on the main figure in magenta.
plot3(xs, ys, zs, 'm-', 'LineWidth', 2);
legend('Original Knots', 'Spline Fit', 'Clipped');

fprintf('Done running %s.m ...\n', mfilename);

In the plot below, the original data is in blue, the spline fit is in red, and the curve clipped to the small box with 0-to-1 range is in magenta: