How to generate the modeling of particle environment

How to generate the modeling of particle environment in a room contains a circular obstacle. just I'll know how to trace the edges, size of the room and the obstacle by points (and the plot() command) on Matlab.

</matlabcentral/answers/uploaded_files/79502/okaaay.JPG> like this image. Thank you

Answer 1

[Image Analyst]

Try this. Adapt as needed:

% Initialization steps.
clc;    % Clear the command window.
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 = 20;

% Make a circular image mask.
% Adapted from FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F
% Create a logical image of a circle with specified
% diameter, center, and image size.
% First create the image.
imageSizeX = 640;
imageSizeY = 240;
[columnsInImage, rowsInImage] = meshgrid(1:imageSizeX, 1:imageSizeY);
% Next create the circle in the image.
centerX = 320;
centerY = 120;
radius = 70;
circlePixels = (rowsInImage - centerY).^2 ...
    + (columnsInImage - centerX).^2 <= radius.^2;
% circlePixels is a 2D "logical" array.
% Now, display it.
subplot(2, 2, 2);
image(circlePixels) ;
axis image;
title('Binary image of a circle', 'FontSize', fontSize);
colormap([0 0 0; 1 1 1]);

% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off') 

numPoints = 500;
% Create pattern of random points with y = 1 to 11 and x = 0 to 32
x = floor(imageSizeX * rand(1, numPoints)) + 1;
y = floor(imageSizeY * 0.9 * rand(1, numPoints) + 0.1 * imageSizeY) + 1;
% Create an image of gray
grayLevel = 64; % Whatever you want between 0 and 255.
grayImage = grayLevel * ones(imageSizeY, imageSizeX, 'uint8');
for k = 1 : numPoints
  grayImage(y(k), x(k)) = 255;
end
subplot(2, 2, 1);
imshow(grayImage);
axis on;
title('Original Points', 'FontSize', fontSize);

% Now mask the image
grayImage(circlePixels) = grayLevel;
subplot(2, 2, 3);
imshow(grayImage);
axis on;
title('Masked Points', 'FontSize', fontSize);

It creates an array of random points. Then it creates a circle mask. Then it erases the points that happened to fall within the circle mask.