NAME Isoband UCD: color filled contour bands on UCD surfaces 

 AUTHOR           Mike French (Evans & Sutherland)

 SUMMARY

     Name:        Isoband UCD

     Type:        mapper 
 
     Inputs:      ucd            ucd  (scalar node values)

                  colormap       colormap (optional)

                  levels         field 1D uniform scalar float (optional)


     Outputs:     contours       geometry 

                  colour bands   colormap


                  name           type       default    min      max
                  ----           ----       -------    ---      ---

     Parameters:  Colourmap      boolean    OFF
                  Boundary

                  N              integer    10          2        20
                  

 DESCRIPTION

     A set of contour bands are drawn on the exterior faces of a UCD.

     The UCD must have a single scalar component of node data. To extract a 
     single scalar component of node data from a composite ucd use the 
     UCD EXTRACT module. There is no module available to extract a scalar 
     from a vector component of node data. 

     The data values for the contours are taken from the 'levels' input field.
     If this input is not present, then the range of the scalar node data is
     divided equally to generate N contour levels. There are always at least
     two contour levels, giving at least one bounded band. If the levels are 
     generated locally then the first and last contour levels are always at 
     the minimum and maximum data values, so the open bands above and 
     below the data range will not be seen. If the levels are generated in
     an INTERVALS UCD module, the local 'N' control parameter is removed.

     If the colour map input is not connected, the contour bands will be 
     given a default greyscale spectrum. If a colour map is present then 
     the scalar node data range is mapped on to the colour value range. 
     Use the COLOR RANGE UCD module to set the colormap lo/hi values 
     to the UCD min/max values.

     If the colour value range has been set using the COLOR RANGE UCD module,
     the colormap range and the node data range will match exactly:
     the band below the minimum level is given the first colour index; 
     and the band above the maximum level is given the last colour index. 
     In general, these underflow/overflow bands will not be visible on the UCD.
 
     If the colour value range is completely within the UCD data range, there
     may be duplicated colours at the bottom and top of the range. If the scalar
     node data range is completely within the colormap range, the contour 
     colours will be a restricted subset of the full gamut of colours.

     The discretized colour map used for the bands is made available as an
     output colormap. This can be displayed using the UCD LEGEND module.
     The underflow/overflow band colours are displayed at the ends of this
     spectrum even though there will not be any bands with these colours in
     the slice. Having such excluded endpoints makes it easy to see when the
     data has overrun the available spectrum. The colormap output can have
     black lines inserted at the band boundaries to simulate the effect of
     the ISOLINE UCD module. These lines are controlled using the
     'Colourmap Boundary' boolean parameter.

 METHOD & BUGS

     See ISOBAND SLICE for details of the contouring method and bugs.

 EXAMPLES

 a) colour contour bands: use the COLOR RANGE UCD module to set the colormap
    range to match the ucd scalar node data.

                                    READ UCD  
	                  		|
        GENERATE COLORMAP   	UCD EXTRACT
       	             |			|
                     |    .-------------o
		     |    |             |
        	COLOR RANGE UCD         |
			  |		|
		          |         UCD CROP
	                  |	    |   |   
                          |  .----------'   
		      .   |  |      |     
                      ISOBAND UCD   |
                             |      |
                             `------o
			            |
                         GEOMETRY VIEWER

 b) black contour lines over coloured isobands: use the COLOR RANGE UCD module
    to set the colormap value range; set the contour levels globally using the
    INTERVALS UCD module; use the STATISTICS module to provide diagnostics
 
                                    READ UCD  
	                  		|
	GENERATE COLORMAP        UCD EXTRACT
                     |		        |
		     |    .-------------o-----------------.
	             |    | 		|		  |
                 COLOR RANGE UCD    UCD CROP	  INTERVALS UCD	
	                  |	    |   |                 |
                          |  .------+---o-----.           |
		          |  |      |         |           |
		      .-----------------o-----------------o
		      |   |  |      |   |  .  |		  |            
                      ISOBAND UCD   |  ISOLINE UCD   STATISTICS
                             |      |         |
                             `------o---------'
				    |
  		        GEOMETRY VIEWER