POLYSHADE Function
Constructs a
shaded surface representation of one or more solids described by a set of polygons.
Usage
Input Parameters
vertices 
A (3, n) array containing the x-, y-, and z-coordinates of each vertex. Coordinates may be in either data or normalized coordinates, depending on which keywords are present.
x, y, z The x-, y-, and z-coordinates of each vertex may alternatively be specified as three individual array expressions; x, y, and z must all contain the same number of elements.
polygons An integer or longword array containing the indices of the vertices of each polygon. The vertices of each polygon should be listed in counterclockwise order when observed from outside the surface. The vertex description of each polygon is a vector of the form [n, i0, i1, ... , in - 1], and the array polygons is the concatenation of the lists of each polygon.
For example, to render a pyramid consisting of four triangles, polygons will contain 16 elements, made by concatenating four 4-element vectors of the form [3, V0, V1, V2]. V0, V1, and V2 are the indices of the vertices describing each triangle.
Returned Value
Keywords
Data Indicates that the vertex coordinates are in data units, the default coordinate system.
Mesh When present and nonzero, a wire-frame mesh is drawn over the polygons, and they are not shaded.
Normal Indicates that coordinates are in normalized units, within the 3D (0,1) cube.
Poly_Shades Similar to the Shades keyword, except one shade per polygon is passed to POLYFILL rather than one shade per vertex.
Shades An array expression, of the same number of elements as vertices, containing the color index at each vertex. The shading of each pixel is interpolated from the surrounding Shades values. For most displays, this keyword should be scaled into the range of bytes. If this keyword is omitted, light source shading is used.
T3d Enables the 3D to 2D transformation contained in the homogeneous 4-by-4 matrix !P.T. If this keyword is set, the system variable !P.T must contain a valid transformation matrix.
XSize The number of columns in the output image array. If omitted, sets the number of columns equal to the x resolution of the currently selected display device.
YSize The number of rows in the output image array. If omitted, sets the number of rows equal to the y resolution of the currently selected display device.
CAUTION: If you are using a PostScript or other high resolution graphics device, you should explicitly specify the XSize and YSize parameters. Making the output image of full device size (the default) will result in an insufficient memory error.
Discussion
TIP: Use the SET_SHADING procedure to control the direction of the light source and other shading parameters.
Example
vol = FLTARR(20, 20, 20)
FOR x = 0, 19 DO FOR y = 0, 19 $
DO FOR z = 0, 19 DO $
vol(x, y, z) = SQRT((x-10)^2 + (y-10)^2 + $
(z-10)^2) + 1.5 * COS(z)
SHADE_VOLUME, vol, 7, v, p
SURFACE, FLTARR(2, 2), /Nodata, /Save, $
XRange = [0, 20], YRange = [0, 20], $
ZRange = [0, 20], XStyle = 4, YStyle = 4, $
ZStyle = 4
image = POLYSHADE(v, p, /T3d)
TV, image
Figure 2-89 Isosurface at level 7 of volume dataset from example.
Figure 2-90 Isosurface at level 7 of volume dataset from example.
See Also
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