1 files changed, 55 insertions, 0 deletions
diff --git a/lib/geometry.c b/lib/geometry.c
new file mode 100644
index 0000000..ec788f1
--- /dev/null
+++ b/lib/geometry.c
@@ -0,0 +1,55 @@
+
+#include "fracture.h"
+
+int edge_to_verts(unsigned int width, bool periodic, unsigned int edge,
+									bool index) {
+	assert(edge < pow(width, 2));
+
+	int x = edge / width + 1;
+	int y = edge % width + 1;
+
+	if (periodic) {
+		return (((index ^ (x % 2)) + 2 * ((y + (index ^ (!(x % 2)))) / 2) - 1) %
+								width +
+						(x - index) * width) /
+					 2;
+	} else {
+		return ((index ^ (x % 2)) + 2 * ((y + (index ^ (!(x % 2)))) / 2) +
+						(x - index) * (width + 1) - 1) /
+					 2;
+	}
+}
+
+int dual_edge_to_verts(unsigned int width, bool periodic, unsigned int edge,
+											 bool index) {
+	assert(edge < pow(width, 2));
+
+	int x = edge / width + 1;
+	int y = edge % width + 1;
+
+	if (periodic) {
+		return (((index ^ (!(x % 2))) + 2 * ((y + (index ^ (x % 2))) / 2) - 1) %
+								width +
+						(x - index) * width) /
+					 2;
+	} else {
+		return ((index ^ (!(x % 2))) + 2 * ((y + (index ^ (x % 2))) / 2) +
+						(x - index) * (width + 1) - 1) /
+					 2;
+	}
+}
+
+double dual_vert_to_coord(unsigned int width, bool periodic, unsigned int vert,
+													bool index) {
+	if (periodic) {
+		if (index)
+			return (2 * vert) % width + (2 * vert / width) % 2;
+		else
+			return 2 * vert / width;
+	} else {
+		if (index)
+			return (2 * vert) % (width + 1);
+		else
+			return (2 * vert) / (width + 1);
+	}
+}