3d point cloud into voxel grid

Hey guys,

i tried to convert a pointcloud of a room created with a laser scanner into a voxel grid, where i can define the size of the voxels like 0.5x0.5x0.5 or even bigger or smaller and then just display all voxels with points from the pointcloud in it.

i tried to use the plotcube.m function in combination with an for loop where i increase the coordinates of the cube like x=0:0.5:18 (where 18 is round about the highst value for x when i plot my pointcloud with scatter3. so i have a loop:

for x=0:0.5:18
    for y=0:0.5:35
        for z=0:0.5:13
            if = 'pointcloudroom.txt' with value
                function plotcube (varagin)
                end
            end
        end

but i don't get behind the "if = 'pointcloudroom.txt' with value" part. I tried to extract the values from a matrix with readmatrix but it didn't work.

any suggestions?

[Matt J]

Please attach sample point cloud data in a .mat file, so that we can demonstrate solutions.

[Sven Hecker]

i attched the pointcloudroom.txt :)

Answer 1

[Matt J]

load data

voxelsize=0.5;
for i=1:3
    tmp=xyz(:,i);

    edges=min(tmp):voxelsize:max(tmp)+voxelsize;

    xyz(:,i)=discretize( tmp , edges);
end

V=accumarray(xyz,1)>0;

volumeViewer(V);

[Sven Hecker]

thank you,

but this is what i get when i try to run this. I named it voxeliz.

>> voxeliz

Error using images.internal.app.volview.checkOpenGLDrivers

Windows Software OpenGL support does not meet the minimum requirement of this app. Try executing the command

"opengl hardware". Type "doc opengl" for more information.

Error in images.internal.app.volview.VolumeViewer/setupApp

Error in images.internal.app.volview.VolumeViewer

Error in volumeViewer (line 61)

images.internal.app.volview.VolumeViewer(varargin{:});

Error in voxeliz (line 9)

volumeViewer(V);

[Sven Hecker]

seems like my MATLAB or hardware isn't made for this, is it?

[Matt J]

You should do as the error message advises. Use "opengl hardware".

[Sven Hecker]

i did. but then i get the warning: Unable to select hardware OpenGL rendering.

[Matt J]

It seems your graphics hardware doesn't have OPENGL. However, the volume V has been computed sucessfully. You can use whatever alternative viewing app you wish to inspect it.

[Sven Hecker]

Yeah, I tried imshow already and could inspect the different layer (that's what it seems like). Thank you very much for your help!!!

[Walter Roberson]

Windows Software OpenGL support does not meet the minimum requirement of this app.

That message can occur when you use remote access such as Terminal Services to a Windows machine, or when you run Windows in a Virtual Machine (I think).

[Sven Hecker]

oh, yes I'm using remote access to my university account....

Answer 2

[Walter Roberson]

See https://www.mathworks.com/matlabcentral/answers/892652-anybody-help-me-by-providing-matlab-code-for-the-three-dimensional-histograms#answer_863405

In particular, the variable occupied in that code is the binary occupancy grid. The code there also plots the cubes.

The code there is intended to be able to handle different classes and figure out the majority occupancy for any given voxel, and color appropriately. It does indeed figure out the majority occupancy, but as yet I am having trouble with the colorization.