Create material abstraction

src/material.c

@@ -0,0 +1,12 @@
+#include "material.h"
+
+bool scatter_lambertian(
+    material_params_t params, hit_t hit, rng_t *rng, ray_t *ray,
+    vec3_t *atten_out)
+{
+	const vec3_t dir = vec3_unit(vec3_add(hit.normal, rng_vec3(rng)));
+	ray->orig = hit.point;
+	ray->dir = vec3_len(dir) == 0 ? hit.normal : dir;
+	*atten_out = params.lambertian.albedo;
+	return true;
+}