0th

Percentile

Calculates global shadow map for a elevation matrix by propogating rays from each matrix point to the light source(s), lowering the brightness at each point for each ray that intersects the surface.

##### Usage
ray_shade(heightmap, anglebreaks = seq(40, 50, 1), sunangle = 315,
maxsearch = 100, lambert = TRUE, zscale = 1, multicore = FALSE,
cache_mask = NULL, shadow_cache = NULL, progbar = TRUE, ...)
##### Arguments
heightmap

A two-dimensional matrix, where each entry in the matrix is the elevation at that point. All points are assumed to be evenly spaced.

anglebreaks

Default seq(40,50,1). The azimuth angle(s), in degrees, as measured from the horizon from which the light originates.

sunangle

Default 315 (NW). The angle, in degrees, around the matrix from which the light originates. Zero degrees is North, increasing clockwise.

maxsearch

Default 100. The maximum distance that the system should propogate rays to check. For longer

lambert

Default TRUE. Changes the intensity of the light at each point based proportional to the dot product of the ray direction and the surface normal at that point. Zeros out all values directed away from the ray.

zscale

Default 1. The ratio between the x and y spacing (which are assumed to be equal) and the z axis. For example, if the elevation levels are in units of 1 meter and the grid values are separated by 10 meters, zscale would be 10.

multicore

Default FALSE. If TRUE, multiple cores will be used to compute the shadow matrix. By default, this uses all cores available, unless the user has set options("cores") in which the multicore option will only use that many cores.

Default NULL. A matrix of 1 and 0s, indicating which points on which the raytracer will operate.

Default NULL. The shadow matrix to be updated at the points defined by the argument cache_mask. If present, this will only compute the raytraced shadows for those points with value 1 in the mask.

progbar

Default TRUE. If FALSE, turns off progress bar.

...

Additional arguments to pass to the makeCluster function when multicore=TRUE.

##### Value

Matrix of light intensities at each point.

##### Examples
# NOT RUN {
#Here we produce an shadow map of the volcano elevation map with the light from the NE.
#The default angle is from 40-50 degrees azimuth, from the north east.

#Turn off Lambertian shading to get a shadow map solely based on the raytraced shadows.