k-Wave User Forum » Topic: How to rotate arc (circle) source

k-Wave User Forum » Topic: How to rotate arc (circle) source http://www.k-wave.org/forum/topic/how-to-rotate-arc-circle-source Support for the k-Wave MATLAB toolbox en-US Tue, 12 May 2026 23:40:54 +0000 http://bbpress.org/?v=1.0.2 <![CDATA[Search]]> q http://www.k-wave.org/forum/search.php Bradley Treeby on "How to rotate arc (circle) source" http://www.k-wave.org/forum/topic/how-to-rotate-arc-circle-source#post-558 Wed, 20 Jun 2012 23:25:37 +0000 Bradley Treeby 558@http://www.k-wave.org/forum/ 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: <pre><code>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));</code></pre> Good luck with your simulations, Brad. neer on "How to rotate arc (circle) source" http://www.k-wave.org/forum/topic/how-to-rotate-arc-circle-source#post-557 Wed, 20 Jun 2012 22:33:26 +0000 neer 557@http://www.k-wave.org/forum/ 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? Bradley Treeby on "How to rotate arc (circle) source" http://www.k-wave.org/forum/topic/how-to-rotate-arc-circle-source#post-183 Tue, 21 Jun 2011 00:21:55 +0000 Bradley Treeby 183@http://www.k-wave.org/forum/ Hi Diwaker, To create a triangular medium, you could do something like: <pre><code>% 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;</code></pre> To define a custom display mask, you will need to add the commands <code>'DisplayMask', your_display_mask</code> after all the other inputs when you call <code>kspaceFirstOrder2D</code>. The display mask must be a binary matrix the same size as your computational grid. The variable <code>medium</code> is actually a structure with several fields (<code>medium.sound_speed</code>, <code>medium.density</code>, 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. Diwaker on "How to rotate arc (circle) source" http://www.k-wave.org/forum/topic/how-to-rotate-arc-circle-source#post-169 Wed, 15 Jun 2011 11:56:06 +0000 Diwaker 169@http://www.k-wave.org/forum/ 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 Bradley Treeby on "How to rotate arc (circle) source" http://www.k-wave.org/forum/topic/how-to-rotate-arc-circle-source#post-161 Mon, 30 May 2011 03:21:49 +0000 Bradley Treeby 161@http://www.k-wave.org/forum/ Hi Diwaker, *How to make right angled triangular mediums? You could use something like <code>triangle = tril(ones(64, 64));</code> 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 <a href="http://www.k-wave.org/documentation/example_ivp_loading_external_image.php">Loading External Image Maps Example</a>. Instead of assigning the loaded image to the initial pressure you could scale it, and then assign it to <code>medium.sound_speed</code> 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 <code>'DisplayMask'</code> 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 <code>getColorMap</code> and replace the line <code>cm = [neg; pos];</code> with <code>cm = gray(num_colors);</code> Kind regards, Brad. Diwaker on "How to rotate arc (circle) source" http://www.k-wave.org/forum/topic/how-to-rotate-arc-circle-source#post-160 Wed, 25 May 2011 07:33:23 +0000 Diwaker 160@http://www.k-wave.org/forum/ 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 Bradley Treeby on "How to rotate arc (circle) source" http://www.k-wave.org/forum/topic/how-to-rotate-arc-circle-source#post-141 Thu, 05 May 2011 09:31:10 +0000 Bradley Treeby 141@http://www.k-wave.org/forum/ 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 <code>makeCircle</code>, 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 <a href="http://www.k-wave.org/documentation/example_tvsp_transducer_field_patterns.php">Simulating Transducer Field Patterns Example</a> 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: <pre><code>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;</code></pre> I hope that helps, Brad. Diwaker on "How to rotate arc (circle) source" http://www.k-wave.org/forum/topic/how-to-rotate-arc-circle-source#post-140 Thu, 05 May 2011 08:35:40 +0000 Diwaker 140@http://www.k-wave.org/forum/ 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?