vlmget_slice4d

NAME

SYNOPSIS

    #include <vlmeta.h>

    int vlmget_slice4d(int ncid,vlmeta_voxel4d * vdata, long voxel_start[], long voxel_count[], int dtype);

DESCRIPTION

    Vlmget_slice4d reads a slice of data values from a ParVox voxel data file. The handle ncid, which is obtained by a previous vlmopen_vox call, points to the file to read from. Vlmget_slice4d reads in the header data in the vlmeta_voxel4d structure vdata and allocates memory for the data at the vldata->voxel_data member if it does not exist. The function then reads from the data location starting from voxel_start and extending voxel_count distance. Dtype indicates the format the file is in, either VL_RAW or VL_NETCDF.

    When selecting a slice to read, the arrays voxel_start and voxel_count are 4 dimensional vectors in the following order: variable ID, depth (k), height (j), and width (i). To put it another way, voxel_start[0] would be the variable number (0 if there is only one), voxel_start[1] would be the value in k dimension, and so on. Note that voxel_count is the extent to read in each direction, therefore no values in voxel_count should be 0. Example: given a dataset of one variable and the size 640 × 480 × 128, suppose we want to read a slice 2 units thick in the k direction, say from (0, 0, 4) to (639, 479, 5). To read this slice, vlmget_slice4d will need to be called with these values in the arrays:

    voxel_start[0] = 0, voxel_start[1] = 4, voxel_start[2] = 0, voxel_start[3] = 0
    voxel_count[0] = 1, voxel_count[1] = 2, voxel_count[2] = 480, voxel_count[3] = 640

    There are a few pitfalls to look out for: first, the voxel_count[] array should contain the extent in each direction, not the absolute ``corner point''. For example, to read one variable, voxel_count[0] = 1. Second, note the order in the array. It is in (variable, k, j, i) order.

SEE ALSO

DIAGNOSTICS