Hi,
I have been trying to get the arc source emitting vertically downwards. I think, one needs to rotate the circle for it. Else, it automatically chooses to start somewhere around the left corner of the figure window producing the diagonal propagation.
Is there a way to make the circle emit straight downwards?
Hi Diwaker,
The source shape is defined as a binary matrix (i.e., a matrix of 1's and 0's) where the 1's (or 'trues') correspond to the source elements within the grid. This can be anything you want.
If you are using the function makeCircle, this creates a binary mask of a circle using the midpoint circle algorithm based on the input parameters, one of which is the arc angle. Within the function, this is defined clockwise from the negative x-axis. As such, a 90° arc as in the Simulating Transducer Field Patterns Example will point diagonally across the domain from the top left to the bottom right.
If you want to create an arc pointing in another direction, you can create a complete circle in the position you require, and then mask out the elements you don't need. For example, to create an arc pointing downwards you could use something like:
Nx = 128;
Nz = 128;
arc_radius = 20;
arc_height = 10;
x_pos = Nx/2;
z_pos = 25;
arc = makeCircle(Nx, Nz, x_pos, z_pos, arc_radius);
arc(z_pos - arc_radius + arc_height:end, :) = 0;
imagesc(arc);
axis image;I hope that helps,
Brad.
Hi Brad,
I was on holidays for 2 weeks. I tried your solution yesterday it worked nicely. Thank you very very much.
I yet have another problem. I want to create a Heterogeneous medium of type, Water-Glass-Water. The glass has to be right angled triangle.
*How to make right angled triangular mediums?
*Is it possible to load arbitrary shapes as images and make them work as medium?
*Can medium be made visible on the running simulation, may be as a color patch or a faint border?
*Can the color-map of the animated plot be changed to gray-scale?
I appreciate you support,
thanks
Diwaker
Hi Diwaker,
*How to make right angled triangular mediums?
You could use something like triangle = tril(ones(64, 64)); to create the triangle, and then place it within a larger matrix where you need it.
*Is it possible to load arbitrary shapes as images and make them work as medium?
Yes. See the Loading External Image Maps Example. Instead of assigning the loaded image to the initial pressure you could scale it, and then assign it to medium.sound_speed etc.
*Can medium be made visible on the running simulation, may be as a color patch or a faint border?
You can set a custom display mask using the 'DisplayMask' input, but this only has limited functionality. The mask must be binary and is displayed as black.
*Can the color-map of the animated plot be changed to gray-scale?
Yes. Open getColorMap and replace the line cm = [neg; pos]; with cm = gray(num_colors);
Kind regards,
Brad.
Thank you Brad,
I am new to MATLAB. A small syntax as to be used in the program would be really nice.
Whenever, I tried to use triangular binary medium, there is an error of uneven X,Y and Z vector.
I couldn't get external image loaded as medium like we do in source {source.p}, can you write a sample command?
Sample command also to make the medium visible is requested. I used Display_mask=medium, this resulted error.
Changing color-map succeeded nicely.
Thank you very much for availing such a wonderful tool.
regards,
Diwaker
Hi Diwaker,
To create a triangular medium, you could do something like:
% define literals
Nx = 128;
Nz = 128;
triangle_size = 32;
triangle_x_pos = 32;
triangle_z_pos = 64;
triangle_sound_speed = 3000;
water_sound_speed = 1500;
% create medium
medium.sound_speed = zeros(Nz, Nx);
medium.sound_speed(triangle_z_pos:triangle_z_pos + triangle_size - 1, ...
triangle_x_pos:triangle_x_pos + triangle_size - 1) ...
= tril(ones(triangle_size));
medium.sound_speed(medium.sound_speed == 1) = triangle_sound_speed;
medium.sound_speed(medium.sound_speed == 0) = water_sound_speed;
% display medium
figure;
imagesc(medium.sound_speed);
axis image;
colorbar;To define a custom display mask, you will need to add the commands 'DisplayMask', your_display_mask after all the other inputs when you call kspaceFirstOrder2D. The display mask must be a binary matrix the same size as your computational grid. The variable medium is actually a structure with several fields (medium.sound_speed, medium.density, etc). You will need to address the fields directly if you want to use them as a display mask.
I hope that helps with your project.
Kind regards,
Brad.
Hi Brad,
I visited the above thread as my requirements are similar to Mr. Diwaker. I want to construct a rotated sensor mask in the form of an arc. The problem is when I construct the initial complete circle, it does not fit within the grid space. In other words my question is, is it possible to construct a completely fitting arc with included angle less than pi?
Hi Neer,
You could create a full circle with the required radius (making the circle grid size big enough to contain it), then copy the part you need to your sensor mask. For example, something like:
circle = makeCircle(2*radius+1, 2*radius+1, radius+1, radius+1, radius);
sensor.mask = circle(1:Nx, round(end/2 - Ny/2)+1:round(end/2 + Ny/2));Good luck with your simulations,
Brad.
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