Data commit

Task/Ray-casting-algorithm/R/ray-casting-algorithm-1.r

@@ -0,0 +1,44 @@
+point_in_polygon <- function(polygon, p) {
+  count <- 0
+  for(side in polygon) {
+    if ( ray_intersect_segment(p, side) ) {
+      count <- count + 1
+    }
+  }
+  if ( count %% 2 == 1 )
+    "INSIDE"
+  else
+    "OUTSIDE"
+}
+
+ray_intersect_segment <- function(p, side) {
+  eps <- 0.0001
+  a <- side$A
+  b <- side$B
+  if ( a$y > b$y ) {
+    a <- side$B
+    b <- side$A
+  }
+  if ( (p$y == a$y) || (p$y == b$y) ) {
+    p$y <- p$y + eps
+  }
+  if ( (p$y < a$y) || (p$y > b$y) )
+    return(FALSE)
+  else if ( p$x > max(a$x, b$x) )
+    return(FALSE)
+  else {
+    if ( p$x < min(a$x, b$x) )
+      return(TRUE)
+    else {
+      if ( a$x != b$x )
+        m_red <- (b$y - a$y) / (b$x - a$x)
+      else
+        m_red <- Inf
+      if ( a$x != p$x )
+        m_blue <- (p$y - a$y) / (p$x - a$x)
+      else
+        m_blue <- Inf
+      return( m_blue >= m_red )
+    }
+  }
+}

Task/Ray-casting-algorithm/R/ray-casting-algorithm-2.r

@@ -0,0 +1,13 @@
+######## utility functions #########
+
+point <- function(x,y) list(x=x, y=y)
+
+# pts = list(p1, p2, ... )... coords
+# segs = list(c(1,2), c(2,1) ...) indices
+createPolygon <- function(pts, segs) {
+  pol <- list()
+  for(pseg in segs) {
+    pol <- c(pol, list(list(A=pts[[pseg[1]]], B=pts[[pseg[2]]])))
+  }
+  pol
+}

Task/Ray-casting-algorithm/R/ray-casting-algorithm-3.r

@@ -0,0 +1,26 @@
+#### testing ####
+
+pts <- list(point(0,0), point(10,0), point(10,10), point(0,10),
+            point(2.5,2.5), point(7.5,2.5), point(7.5,7.5), point(2.5,7.5),
+            point(0,5), point(10,5),
+            point(3,0), point(7,0), point(7,10), point(3,10))
+
+polygons <-
+  list(
+       square = createPolygon(pts, list(c(1,2), c(2,3), c(3,4), c(4,1))),
+       squarehole = createPolygon(pts, list(c(1,2), c(2,3), c(3,4), c(4,1), c(5,6), c(6,7), c(7,8), c(8,5))),
+       exagon = createPolygon(pts, list(c(11,12), c(12,10), c(10,13), c(13,14), c(14,9), c(9,11)))
+      )
+
+testpoints <-
+  list(
+       point(5,5), point(5, 8), point(-10, 5), point(0,5), point(10,5),
+       point(8,5), point(9.9,9.9)
+      )
+
+for(p in testpoints) {
+  for(polysi in 1:length(polygons)) {
+    cat(sprintf("point (%lf, %lf) is %s polygon (%s)\n",
+                  p$x, p$y, point_in_polygon(polygons[[polysi]], p), names(polygons[polysi])))
+  }
+}