resample a rectilinear field to reduce (or increase) its size
group DVdownsize_rect {
Mesh_Rect+Node_Data+Iparam &in {
xform+nonotify;
nnodes+req;
};
float+Iparam factor[in.ndim];
Mesh_Rect+Node_Data+Oparam out{
&xform<weight=-1> => in.xform;
};
method+notify_val+notify_inst upd_downsize = "downsize";
} ;
DVdownsize_rect resamples a rectilinear field (mesh type Mesh_Rect) using a scaling factor. Where the factor is > 1, DVdownsize reduces the size of the field, saving processing time and memory by "thinning out" the data. Where factor < 1, DVdownsize_rect increases the size of the field by duplicating data.
DVdownsize_rect works like this (see the 1D example on the following page):
For each dimension i (X, Y, and Z) calculate:
• dims_out[i] = dims_in[i] / factor[i]
•
Round dims_out up or down to the nearest whole integer.
Note: the two endpoints are always preserved in the output data.
Note: the extents of the input field are preserved in the output field.
• Calculate the ratio of the intervals between nodes dims_in : dims_out
• For each new array index, find the nearest whole integer by rounding up or down.
• Use the node data and coordinates in the input field that are found by these index values as the node data and coordinates for the output field.
Note that, throughout the process, the actual node data values and coordinate values are irrelevant. All that is being manipulated are the indexes into these arrays.
A reference to an input field containing a Mesh_Rect and Node_Data.
A float array used as a scaling coefficient. The output field's values (and coordinates for irregular data) are:
dims_out[i] = dims_in[i] / factor [i]
where i cycles through the dims of the field, either 1D, 2D, or 3D.
The length of the factor array (1D: just X; 2D: X and Y; 3D: X, Y and Z) is taken from the ndim of the Grid_Struct. You control the factor for each dimension separately.
Note: factors < 1 will make the output field larger. For example, a factor of 0.5 will double the size of the output field.
The output is a new object that contains a new Mesh_Rect. The new Mesh_Rect's points array (extents) will occupy the same "space" as the input field's Mesh_Rect.
The output field also contains a new Node_Data object containing the data associated with the downsized region.