r3.mkdspf

Usage:
 r3.mkdspf [-qf] input=name out=name [levels=value[,value,...]]
   [min=value] [max=value] [step=value] [tnum=value]

Flags:
  -q   Suppress progress report & min/max information
  -f   Use flat shading rather than gradient

Parameters:
   input   Name of an existing 3dcell map
     out   Name of output display file
  levels   List of thresholds for isosurfaces
     min   Minimum isosurface level
     max   Maximum isosurface level
    step   Positive increment between isosurface levels
    tnum   Number of isosurface threshold levels
           default: 7

Creates a display file from an existing grid3 file according to specified threshold levels. The display file is a display list of polygons that represent isosurfaces of the data volume. The polygons that make up a single isosurface are determined using the "marching cubes" algorithm. Normals for the vertices are also calculated and stored in the display file. If specific threshold levels are given, additional optional parameters are ignored. Min or max may be used alone or together to specify a sub-range of the data. The step parameter is given precedence over tnum.

Example:

With grid3 data (phdata) in the range 3-7, we only want to see isosurface values for the range 4-6. Any of these commands will produce the same results:

r3.mkdspf phdata out=iso min=4.0 max=6.0 tnum=5
r3.mkdspf phdata out=iso levels=4.0,4.5,5.0,5.5,6.0
r3.mkdspf phdata out=iso min=4.0 max=6.0 step=0.5

Note:

Currently the grid3 file must be in the user's mapset since the display files being created are specific to particular grid3 files and are contained in directories under them. We should create a mechanism where users may make display files from others' grid3 files without having to copy them to their mapset. Also, we should upgrade the program to use the current 3D region to allow quick subsampling of large data sets.

References

Lorensen, W. E. and Cline, H. E., "Marching Cubes: A High Resolution 3D Surface Construction Algorithm," Computer Graphics, vol. 21, no. 3, pp. 163-169, July 1987.

Authors

Bill Brown, Terry Baker, Jan Moorman, David Gerdes