From f66e306e8ff997a413ba318e9d64220debda4bd7 Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cobrien@witekio.com>
Date: Tue, 23 Sep 2025 15:35:26 +0100
Subject: [PATCH] Add rng_xy()

---
 include/rng.h | 1 +
 src/rng.c     | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/include/rng.h b/include/rng.h
index d1252b8..276e3d3 100644
--- a/include/rng.h
+++ b/include/rng.h
@@ -14,6 +14,7 @@ uint32_t rng_uint32(rng_t *rng);
 double rng_canon(rng_t *rng);
 double rng_plusminus(rng_t *rng);
 vec3_t rng_vec3(rng_t *rng);
+vec3_t rng_xy(rng_t *rng);
 vec3_t rng_gaussian_xy(rng_t *rng, double stddev);
 
 #endif
diff --git a/src/rng.c b/src/rng.c
index 3ba51d8..0dc30c4 100644
--- a/src/rng.c
+++ b/src/rng.c
@@ -42,6 +42,13 @@ vec3_t rng_vec3(rng_t *rng)
 	return vec3_unit(v);
 }
 
+vec3_t rng_xy(rng_t *rng)
+{
+	const double theta = 2.0 * M_PI * rng_canon(rng);
+	const double mag = rng_canon(rng);
+	return (vec3_t) { .x = mag * cos(theta), .y = mag * sin(theta) };
+}
+
 vec3_t rng_gaussian_xy(rng_t *rng, double stddev)
 {
 	const double r1 = rng_canon(rng);