Editing VOL
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| − | A '''VOL''' primitive represents a three-dimensional grid of cells, also referred to as voxels, which are each either solid or empty. It is defined by a three-dimensional array of unsigned char values | + | A '''VOL''' primitive represents a three-dimensional grid of cells, also referred to as voxels, which are each either solid or empty. It is defined by a three-dimensional array of unsigned char values, where each value represents a cell that is solid if the value lies between the primitive's given upper and lower thresholds, inclusively. |
| − | + | Specific information about the creation of a VOL primitive is available in the [[BRL-CAD Primitives#vol | list of primitives]]. | |
| − | ==Inserting | + | ==Inserting volume data of a CT scan in MGED == |
| − | Stanford hosts an [http://graphics.stanford.edu/data/voldata/ archive of | + | Stanford hosts an [http://graphics.stanford.edu/data/voldata/ archive of volume data] for testing purposes. |
For this example, let's use the first set of data: "CT study of a cadaver head". It contains 113 files of two-dimensional data with a resolution of 256x256. Each file represents one slice, so we'll need to concatenate them into one file to be able to import it into MGED. In addition, the data is in the form of 16-bit unsigned integers, so we'll need to use '''cv''' to convert it into unsigned chars. | For this example, let's use the first set of data: "CT study of a cadaver head". It contains 113 files of two-dimensional data with a resolution of 256x256. Each file represents one slice, so we'll need to concatenate them into one file to be able to import it into MGED. In addition, the data is in the form of 16-bit unsigned integers, so we'll need to use '''cv''' to convert it into unsigned chars. | ||
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$ cat $(ls -v scanslices/*) > scandata16 | $ cat $(ls -v scanslices/*) > scandata16 | ||
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Convert ''scandata16'' from 16-bit little-endian unsigned integers to big-endian unsigned chars using '''cv''' and write the data to ''scandata8'': | Convert ''scandata16'' from 16-bit little-endian unsigned integers to big-endian unsigned chars using '''cv''' and write the data to ''scandata8'': | ||
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=== Importing into MGED === | === Importing into MGED === | ||
| − | The data in ''scandata8'' should now be ready to be imported into MGED | + | The data in ''scandata8'' should now be ready to be imported into MGED. |
mged> in | mged> in | ||
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Enter lower threshold value: 8 255 | Enter lower threshold value: 8 255 | ||
Enter X, Y, Z dimensions of a cell: 1 1 1 | Enter X, Y, Z dimensions of a cell: 1 1 1 | ||
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| + | ERROR: bad pointer 0x1cd74f0: s/b rt_ebm_internal(xf901b231), was rt_vol_internal(x987ba1d0), file /home/jordi/Escriptori/brlcad-7.24.2/src/librt/primitives/vol/vol.c, line 760 | ||
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| + | Whoops. I must have done something wrong. | ||
