Random() issues with rendering...

- AO and soft shadow AreaLight tables were generated without fixed seed,
  causing animations to give unwanted amounts of noise.
- Made sure these tables now are calculated before render, with fixed seed
- Then found out the BLI_rand() has very bad seeding... it showed up as
  patterns. After some experimenting, found a nice method using noise.c
  hash tables. For compatibility with old code, named it BLI_srandom() to
  use this next to the BLI_srand(). This follows libc rand() and random()
  naming convention.
- Then of course threading should work... so made a BLI_thread_rand version
  of the calls. Now supports up to 16 threads, comments added in .h and .c

Result is stable animation render with AO and soft shadow. But, please
test and feedback!

1 files changed, 18 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_rand.h b/source/blender/blenlib/BLI_rand.h
index e6b0146cfab..da2ecb79651 100644
--- a/source/blender/blenlib/BLI_rand.h
+++ b/source/blender/blenlib/BLI_rand.h
@@ -55,6 +55,9 @@ void		rng_shuffleArray(struct RNG *rng, void *data, int elemSize, int numElems);
 	/** Seed the random number generator */
 void	BLI_srand		(unsigned int seed);
 
+	/** Better seed for the random number generator, using noise.c hash[] */
+void	BLI_srandom		(unsigned int seed);
+
 	/** Return a pseudo-random number N where 0<=N<(2^31) */
 int		BLI_rand		(void);
 
@@ -77,5 +80,20 @@ void	BLI_fillrand	(void *addr, int len);
 	 */
 void	BLI_array_randomize	(void *data, int elemSize, int numElems, unsigned int seed);
 
+
+	/** Better seed for the random number generator, using noise.c hash[] */
+	/** Allows up to 16 threads to address */
+void	BLI_thread_srandom	(int thread, unsigned int seed);
+
+	/** Return a pseudo-random number N where 0<=N<(2^31) */
+	/** Allows up to 16 threads to address */
+int		BLI_thread_rand		(int thread);
+
+	/** Return a pseudo-random number N where 0.0f<=N<1.0f */
+	/** Allows up to 16 threads to address */
+float	BLI_thread_frand	(int thread);
+
+
+
 #endif