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Re: Problems during Generation of a Spherical Point Cloud
Posted:
Jul 24, 2010 11:45 PM


Hi, Nic,
Thanks for your help.
SphereArray=XYZD2Sphere(BW,XYZD);
I want to generate a binary point cloud of a sphere in an array as same size as the input BW. The XYZD is a 4element vector. The first 3 elements are the XYZ coordinates of the sphere's center point and the 4th element is the diameter of the sphere.
For example: SphereArray=XYZD2Sphere(false(128,128,128),[50 60 70 30]); patch(isosurface(SphereArray,0));
will get an output SphereArray a 128128128 binary array with a 30cm diameter sphere (trues) located around center point [50 60 70].
But now the sphere centers at [60 50 70]. I guess the x and y axis swap. I cannot find the errors from the code.
"Nic Roberts" <dingtheking@googlemail.com> wrote in message <i2bpem$9ug$1@fred.mathworks.com>... > Hi Joseph > > It isnt imediatly apparent from your code what it is you are trying to achieve. When I run your code I just get a massive array of zeros. Is your intent to remove a sphere of data from BW? > > Nic > > "Joseph " <wg_smile4ever@hotmail.com> wrote in message <i2bil4$aqh$1@fred.mathworks.com>... > > Hi, all, > > > > I am new to Matlab and using it for image processing. > > I am writing a function to generate a point cloud of a sphere on a 3D image the size of which is same as the input image BW. Another input XYZD is a 4element vector containing the X,Y and Z positions of the center point and the diameter of the sphere. The output of the function SphereBW is the new 3D image with the sphere point cloud. > > > > The code is pasted below: > > > > function SphereBW=XYZD2Sphere(BW,XYZD) > > > > SphereBW=false(size(BW,1),size(BW,2),size(BW,3)); > > > > cx=XYZD(1);cy=XYZD(2);cz=XYZD(3);diameter=XYZD(4); > > > > for x=1:size(BW,1) > > for y=1:size(BW,2) > > for z= 1:size(BW,3) > > if (xcx)^2+(ycy)^2+(zcz)^2<(diameter/2)^2 > > SphereBW(x,y,z)=1; > > end > > end > > end > > end > > > > end > > > > > > But the sphere I generate is put to a wrong location in the new image where it seems that the X and Y coordinates are swapped. > > e.g. if my input BW size is [512 512 100] and XYZD vector is [250 150 50 30] > > the center point of the sphere locates at [150 250 50] in the output image SphereBW. > > > > Please help me to figure out what is wrong with my function. If you know how to write any other elegant codes (without for loops), please teach me as well. > > > > Many thanks!!! > > > > Joseph



