Hi,
I want to analyse the sound wave reflected from a moving skeleton inside a room.
First, how can I model the skeleton in the medium if I have the 3d joint coordinates of the skeleton for each frame. Or how can I improt 3d object inside the medium.
I want to analyse the reflected signal for every frame seperately.
Best regards,
bashjokh
Hi bashjokh,
As k-wave works on a cartesian grid, I would advise you to voxelize your mesh. This script does the job: Matlab voxelisation script
Then, you can define a binary mask and consider the points as mass source or velocity source (depending on the boundary conditions you want to put on your skeleton). I would also set the optional argument source.p_mode or source.u_mode to 'dirichlet' (see p34 or the user manual).
Hope it helps,
Anthony
Hello Hyperomi,
thanks for your reply, first my model is represented only as 3d cartesian coordinates without any faces or normals. How can I assign different medium properties(sound speed and density) for this points or for the lines jointing this coordinates?
I have already started as following :
% define the position of the object
object_y_pos = Ny/2 - 10 ;
object_x_pos = Nx/4;
object_z_pos = Nz/2;
object = zeros(Nx, Ny, Nz);
object(object_x_pos : end - end/4, object_y_pos : object_y_pos + thickness,object_z_pos: object_z_pos + thickness) = 1;
% assign the medium properties
medium.sound_speed = c_air*ones(Nx, Ny, Nz);
medium.sound_speed(object == 1) = c_object;
medium.density = rho_air*ones(Nx, Ny, Nz);
medium.density(object == 1) = rho_object;
However this is for the coordinates inside the medium which I already know. But now how can I set the same properties for my skeleton which is represented with 3d lines connecting the joints.
Thanks in advance
Hi bashjokh,
I am not sure to understand what you mean:
--> you have the coordinates of the joints of your skeleton and want to set the material properties along 1D lines that represent the "bones" of your skeleton?
If I understand well, your problem is therefore to define the binary mask, (for a given voxel : 1 if a line crosses the voxel, else 0).
If yes, you could for example:
- store the coordinates of the 8 corners of each voxels
- vectorize this type of algorithm (to make it efficient with matlab)
here
Another solution would be to adapt the function makeLine (coming with kwave) in 3D (I didn't check how it works but it should be doable).
Hope it helps and sorry if I didn't get your problem...
Anthony
Dear Anthony,
thanks for your answer, that's exactly what I want to do. But the bones of the skeleton should be represented not as 1D line connecting the joints but possibly as cylinders.
I'll will try to implement what did you say.
Many thanks,
bashjokh
Dear bashjokh,
Another (faster) way to do it for a 1D line, would be to compute the distance between the center of each voxel to the line (using the analytical formula based on dot product). If it is smaller than dx*sqrt(3)/2 (the half diagonal of the voxel, assuming it is a cube), then the point belongs to the line.
For a cylinder, just replace 'smaller than dx*sqrt(3)/2' by 'smaller than the radius of the cylinder' :-)
Regards,
Anthony
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