Randomise scene

include/rng.h

@@ -10,7 +10,9 @@ typedef struct {
 } rng_t;
 
 rng_t rng_init(unsigned seed);
+uint32_t rng_uint32(rng_t *rng);
 double rng_canon(rng_t *rng);
+double rng_disc(rng_t *rng);
 vec3_t rng_vec3(rng_t *rng);
 vec3_t rng_gaussian_xy(rng_t *rng, double stddev);