AVS Modules						        texture mesh
Lawrence Berkeley Laboratory				       4 August 1992

NAME
     texture mesh - create quad mesh from 2d field; support for 
	texture mapping

SUMMARY
     Name	   texture mesh

     Type	   mapper

     Inputs	   2D field scalar float, uniform | rectilinear | irregular
                            (REQUIRED)
		   2D image (scalar 4-vector byte)
			    (OTIONAL)

     Outputs	   Geometry - quad mesh

     Parameters	   
     Name               Type        Default       Min       Max
     Texture Mapping Options
			choice	    "dynamic"	 "dynamic","explicit"
     Surface UV Coordinates Minimum
			string	    "0. 0."	 none	    none
     Surface UV Coordinates Maximum
			string	    "1. 1."	 none	    none
     Explicit Mapping Interpolation
		    	choice	    "point"	 "point", "bilinear"

DESCRIPTION

	The texture mesh module serves two needs.  First, the need for
 	a robust module for mapping 2D data to quadrilateral meshes
	is served.  The input 2D data may be a 2D uniform field, in
	which case the x,y coordinates for the output mesh is derived
	from the extents information (if present) or using a mapping
	from indeces to space if no extents information is present.  The
	z values are obtained from the data in the field.

	In 2D rectilinear fields, the x,y coordinates are explicitly
	provided.  The z values are obtained from the data.

	In 2D, 3-space irregular fields, all coordinates are specified.
	In 2D, 2-space irregular fields, the mapping is the same as
	in rectilinear data.

	The second need fulfilled by this module is support for texture
	mapping.  Two types are supported.  The first, called "dynamic"
	in AVS parlance, is the traditional type of texture mapping where
	the coloring of the surface is postponed until rendering time.
	The second type, called "explicit" here will color the vertices
	of the field based upon the image on the second input port, along
	with the uv coordinate ranges specified by the user.

	Control over the uv coordinates is explicitly supported for this
	module so that the user may move the texture around, or scale the
	texture using the parameters provided.  Non-affine transformations
	along with rotations (of textures on the surface) are not
	supported.

INPUTS

	Field data; field 2D scalar float (REQUIRED): the field may be
		one of the following:
		1. 2D uniform, with or without extents
		2. 2D rectilinear
		3. 2D irregular, 3-space
		4. 2D irregular, 2-space

	Texture data (OPTIONAL) ; field 2D 4-vector byte

PARAMETERS

	Texture Mapping Options:
		This set of radio buttons is used to select the type
		of texture mapping.  With dynamic mapping, no data
		is expected on the texture data input port of this 
		module.  However, to get the texture to appear, there
		must be some texture data provided to the geometry 
		viewer, either through the input image port, or using
		the texture editor to select an AVS image file.

	Surface UV Coordinates
		These strings define the placement of the texture on
		the surface.  There is no practical restriction on the
		range of U and V.  If the range of U and V does not 
		include the interval (0..1), no texture will appear
		on the image, regardless of the value of the 
		"texture mapping options" (above).

	Explicit Mapping Interpolation
		The user may control the accuracy of the explicit texture
		mapping operation.  "Point" runs more quickly, but
		"bilinear" gives better results.  "Bilinear" is not
		supported for irregular fields.

OUTPUTS

	Geometry 
		A quadrilateral mesh is produced as output, possibly with
		colors OR UV data (but not both).


EXAMPLE 1.
	The first example shows how to use this module to get the same
	results as if using "field to mesh" supplied with AVS.  Note
	that the texture mesh module DOES NOT provide a "z scale" dial.
	This functionality can be achieved by using a field math module
	if the z values are being obtained from data (and not coordinates).
	

        GENERATE COLORMAP			READ FIELD
            |						|
	    +   +---------------------------------------+
	COLOR RANGE				        |
	    |					        |
            |    				ORTHOGONAL SLICER
	    |   +---------------------------------------+
	COLORIZER                                       |
            |                                           |
	FIELD TO BYTE                                 	|
            +-------------------------------------+     |
				                TEXTURE MESH
						        |
						GEOMETRY VIEWER
	
EXAMPLE 2.
	The second example shows how to do implicit, or "dynamic" 
	texture mapping.  In this case, we are mapping the mandrill
	onto a slice of the hydrogen data.  Note that intervention is
	required in the geometry viewer to get the attention of the
	renderer.

	                         READ FIELD  /* read in hydrogen.fld */ 
	READ IMAGE /* mandrill.x */   |
            |                  ORTHOGONAL SLICER
            |                         |
            |                   FIELD TO FLOAT
            |                         |
            +--------+      +---------+
		  TEXTURE MESH
			 |
		  GEOMETRY VIEWER

	After setting up this network and reading in the various
	data, make the object "textured_mesh" the current object.
	Then, click on "edit texture" in the geometry viewer.
	Next, click on the "set dynamic texture" button.  This will
	tell the renderer that the current object (textured mesh)
	has a "dynamic" texture that needs attention.

	Next, play around with the U and V coordinate min and max
	to get a feel for how these dials work.  Add a field math
	module along the read_field->ortho_slicer->field_to_float
	leg of the network to scale Z values, if desired.

RELATED	MODULES
     field to mesh

LIMITATIONS/KNOWN BUGS
	1. Only float fields are allowed.
	2. No bilinear texture interpolation is provided for
	    irregular fields.


AVS Modules						        texture mesh
Lawrence Berkeley Laboratory				       4 August 1992