SHADE_SURF_IRR Procedure

Standard Library routine that creates a shaded-surface representation of a semiregularly gridded surface, with shading from either a light source model or from a specified array of intensities.


Ax	Noclip	[XYZ]Margin
Az	Nodata	[XYZ]Minor
Background	Noerase	[XYZ]Range
Charsize	Normal	[XYZ]Style
Clip	Position	[XYZ]Tickname
Color	Save	[XYZ]Ticks
Data	T3d	[XYZ]Tickv
Device	Ticklen	[XYZ]Title
Font	[XYZ]Charsize

Discussion

The input data for SHADE_SURF_IRR must be able to be represented as an array of quadrilaterals. This procedure should be used when the (x, y, z) arrays are too irregular to be drawn by the SHADE_SURF procedure, but are still semiregular.

SHADE_SURF_IRR is similar to the SURFACE procedure. Given a semiregular grid of elevations, it produces a shaded surface representation of the data with hidden surfaces removed.

If the graphics output device has scalable pixels (e.g., PostScript), then the output image is scaled so that its largest dimension is less than or equal to 400. Use the Max_Img_Size keyword to increase this size.

When outputting to PostScript devices, the default for the Background keyword is white (index 255), rather than !P.Background.

Use the SET_SHADING procedure to control the direction of the light source and other shading parameters.

NOTE: The NoErase keyword is ignored on devices that do not support TVRD() for example, PostScript.

CAUTION: If the T3d keyword is set, the 3D to 2D transformation matrix contained in !P.T must project the z-axis to a line parallel to the device y-axis, or errors will occur.

Example

This example uses SHADE_SURF_IRR to display a shaded surface over an irregular grid. The function defining the surface is:

x = (LINDGEN(200, 100) MOD 200) / 10.0 - 10.0
y = (LINDGEN(200, 100)  /  200) / 10.0 - 5.0

; Compute x- and y-components of a 200x100 regular grid.

x = x + (RANDOMN(seed, 200, 100) - 2.0) / 16.0
y = y + (RANDOMN(seed, 200, 100) - 2.0) / 16.0

; Build an irregular grid by perturbing the regular grid 

; by a random factor.

z = x * SIN(y) + y * COS(x)

; Compute a two-dimensional array of elevations.

SHADE_SURF_IRR, z, x, y, Ax = 70

; Display the shaded surface. The Ax keyword is used to specify

; the angle of rotation about the x-axis.

Figure 2-109 Shaded surface defined in the example over irregular grid.

Figure 2-110 Shaded surface defined in the example over irregular grid.

SHADE_SURF_IRR Procedure

Usage

Input Parameters

Keywords

Discussion

Example

See Also