From 5d48f61406e64be84e126f5212275908e71ac290 Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cdo@wip.sh>
Date: Tue, 23 Sep 2025 15:36:08 +0100
Subject: [PATCH] Implement RNG module

---
 CMakeLists.txt |  1 +
 demo.c         |  5 +++++
 include/rng.h  | 11 +++++++++++
 src/rng.c      | 23 +++++++++++++++++++++++
 4 files changed, 40 insertions(+)
 create mode 100644 include/rng.h
 create mode 100644 src/rng.c

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b7eb995..c1488c0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,6 +12,7 @@ add_library(batomorph
   src/camera.c
   src/ff.c
   src/obj.c
+  src/rng.c
   src/vec3.c
 )
 configure_target(batomorph)
diff --git a/demo.c b/demo.c
index 15bd1a5..7ec8c1d 100644
--- a/demo.c
+++ b/demo.c
@@ -1,6 +1,7 @@
 #include "camera.h"
 #include "ff.h"
 #include "obj.h"
+#include "rng.h"
 
 #include <unistd.h>
 
@@ -23,9 +24,13 @@ static pix_t pixbuf[W * H];
 
 int main()
 {
+	rng_init();
+
 	img_t img = { .pix = pixbuf };
 	camera_t camera = camera_init(camera_pos, FOCAL_LEN, VIEWPORT_H, W, H);
 	camera_render(&camera, scene, NELEMS(scene), &img);
+
 	ff_write(STDOUT_FILENO, img);
+
 	return 0;
 }
diff --git a/include/rng.h b/include/rng.h
new file mode 100644
index 0000000..17fda3c
--- /dev/null
+++ b/include/rng.h
@@ -0,0 +1,11 @@
+#ifndef RNG_H
+#define RNG_H
+
+#include "vec3.h"
+
+void rng_init();
+
+double rng_double();
+vec3_t rng_vec3();
+
+#endif
diff --git a/src/rng.c b/src/rng.c
new file mode 100644
index 0000000..5bd179e
--- /dev/null
+++ b/src/rng.c
@@ -0,0 +1,23 @@
+#include "rng.h"
+
+#include <limits.h>
+#include <stdlib.h>
+#include <sys/time.h>
+
+void rng_init()
+{
+	struct timeval tv;
+	gettimeofday(&tv, NULL);
+	srand(tv.tv_usec);
+}
+
+double rng_double()
+{
+	return 2.0 * (double)rand() / (double)INT_MAX - 1.0;
+}
+
+vec3_t rng_vec3()
+{
+	const vec3_t v = { rng_double(), rng_double(), rng_double() };
+	return vec3_unit(v);
+}