Module Analytical Hillshading

Analytical hillshading calculation.
Method 'Ambient Occlusion' is based on concepts of Tarini et al. (2006), but only the northern half-space is considered.

References:
Tarini, M. / Cignoni, P. / Montani, C. (2006): Ambient Occlusion and Edge Cueing to Enhance Real Time Molecular Visualization. IEEE Transactions on Visualization and Computer Graphics, Vol. 12, No. 5, pp. 1237-1244.

Author: O.Conrad, V.Wichmann (c) 2003-2013
Specification: grid
Menu: Terrain Analysis|Lighting

Parameters

	Name	Type	Identifier	Description	Constraints
Input	Elevation	Grid (input)	`ELEVATION`	-	-
Output	Analytical Hillshading	Grid (output)	`SHADE`	The angle between the surface and the incoming light beams, measured in radians.	-
Options	Shading Method	Choice	`METHOD`	-	Available Choices: [0] Standard [1] Standard (max. 90Degree) [2] Combined Shading [3] Ray Tracing [4] Ambient Occlusion Default: 0
	Azimuth [Degree]	Floating point	`AZIMUTH`	Direction of the light source, measured in degree clockwise from the north direction.	Default: 315.000000
	Height [Degree]	Floating point	`DECLINATION`	Height of the light source, measured in degree above the horizon.	Default: 45.000000
	Exaggeration	Floating point	`EXAGGERATION`	The terrain exaggeration factor allows to increase the shading contrasts in flat areas.	Default: 4.000000
	Shadow	Choice	`SHADOW`	Choose 'slim' to trace grid node's shadow, 'fat' to trace the whole cell's shadow. The first is slightly faster but might show some artifacts.	Available Choices: [0] slim [1] fat Default: 1
	Number of Directions	Integer	`NDIRS`	Number of sample directions for ambient occlusion. Divides azimuth range (270 to 0 to 90 degree) into sectors. Declination (0 to 90 degree) is devided in (Number of Directions / 4) sectors.	Minimum: 2 Default: 8
	Search Radius	Floating point	`RADIUS`	Radius used to trace for shadows (ambient occlusion) [map units].	Minimum: 0.001000 Default: 10.000000

Command-line

Usage: saga_cmd ta_lighting 0 -ELEVATION <str> [-SHADE <str>] [-METHOD <str>] [-AZIMUTH <str>] [-DECLINATION <str>] [-EXAGGERATION <str>] [-SHADOW <str>] [-NDIRS <num>] [-RADIUS <str>]
  -ELEVATION:<str>   	Elevation
	Grid (input)
  -SHADE:<str>       	Analytical Hillshading
	Grid (output)
  -METHOD:<str>      	Shading Method
	Choice
	Available Choices:
	[0] Standard
	[1] Standard (max. 90Degree)
	[2] Combined Shading
	[3] Ray Tracing
	[4] Ambient Occlusion
	Default: 0
  -AZIMUTH:<str>     	Azimuth [Degree]
	Floating point
	Default: 315.000000
  -DECLINATION:<str> 	Height [Degree]
	Floating point
	Default: 45.000000
  -EXAGGERATION:<str>	Exaggeration
	Floating point
	Default: 4.000000
  -SHADOW:<str>      	Shadow
	Choice
	Available Choices:
	[0] slim
	[1] fat
	Default: 1
  -NDIRS:<num>       	Number of Directions
	Integer
	Minimum: 2
	Default: 8
  -RADIUS:<str>      	Search Radius
	Floating point
	Minimum: 0.001000
	Default: 10.000000