Created
October 8, 2018 08:58
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raytracing volcano dataset in R
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# Code taken from article: http://www.tylermw.com/throwing-shade/ | |
# Author: Tyler Morgan-Wall | |
# License: GPLv3 | |
volcanoshadow = matrix(1, ncol = ncol(volcano), nrow = nrow(volcano)) | |
volc = list(x=1:nrow(volcano), y=1:ncol(volcano), z=volcano) | |
sunangle = 45 / 180*pi | |
angle = -90 / 180 * pi | |
diffangle = 90 / 180 * pi | |
numberangles = 25 | |
anglebreaks = seq(angle, diffangle, length.out = numberangles) | |
maxdistance = floor(sqrt(ncol(volcano)^2 + nrow(volcano)^2)) | |
for (i in 1:nrow(volcano)) { | |
for (j in 1:ncol(volcano)) { | |
for (anglei in anglebreaks) { | |
for (k in 1:maxdistance) { | |
xcoord = (i + sin(sunangle)*k) | |
ycoord = (j + cos(sunangle)*k) | |
if(xcoord > nrow(volcano) || | |
ycoord > ncol(volcano) || | |
xcoord < 0 || ycoord < 0) { | |
break | |
} else { | |
tanangheight = volcano[i, j] + tan(anglei) * k | |
if (all(c(volcano[ceiling(xcoord), ceiling(ycoord)], | |
volcano[floor(xcoord), ceiling(ycoord)], | |
volcano[ceiling(xcoord), floor(ycoord)], | |
volcano[floor(xcoord), floor(ycoord)]) < tanangheight)) next | |
if (tanangheight < akima::bilinear(volc$x,volc$y,volc$z,x0=xcoord,y0=ycoord)$z) { | |
volcanoshadow[i, j] = volcanoshadow[i, j] - 1 / length(anglebreaks) | |
break | |
} | |
} | |
} | |
} | |
} | |
} |
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