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, 38 insertions, 2 deletions

diff --git a/source/blender/blenlib/intern/rand.c b/source/blender/blenlib/intern/rand.c
index 191d63f9748..a8b59fc58f3 100644
--- a/source/blender/blenlib/intern/rand.c
+++ b/source/blender/blenlib/intern/rand.c
@@ -48,7 +48,7 @@ typedef unsigned __int64	r_uint64;
 typedef unsigned long long	r_uint64;
 #endif
 
-#define MULTIPLIER	0x5DEECE66D
+#define MULTIPLIER	0x5DEECE66DLL
 #define ADDEND		0xB
 
 #define LOWSEED		0x330E
@@ -78,7 +78,7 @@ void rng_seed(RNG *rng, unsigned int seed) {
 }
 
 int rng_getInt(RNG *rng) {
-	rng->X= (MULTIPLIER*rng->X + ADDEND)&0x0000FFFFFFFFFFFF;
+	rng->X= (MULTIPLIER*rng->X + ADDEND)&0x0000FFFFFFFFFFFFLL;
 	return (int) (rng->X>>17);
 }
 
@@ -112,10 +112,22 @@ void rng_shuffleArray(RNG *rng, void *data, int elemSize, int numElems)
 
 static RNG theBLI_rng = {0};
 
+/* note, this one creates periodical patterns */
 void BLI_srand(unsigned int seed) {
 	rng_seed(&theBLI_rng, seed);
 }
 
+/* using hash table to create better seed */
+void BLI_srandom(unsigned int seed) {
+	extern unsigned char hash[];	// noise.c
+	
+	rng_seed(&theBLI_rng, seed + hash[seed & 255]);
+	seed= rng_getInt(&theBLI_rng);
+	rng_seed(&theBLI_rng, seed + hash[seed & 255]);
+	seed= rng_getInt(&theBLI_rng);
+	rng_seed(&theBLI_rng, seed + hash[seed & 255]);
+}
+
 int BLI_rand(void) {
 	return rng_getInt(&theBLI_rng);
 }
@@ -144,3 +156,27 @@ void BLI_array_randomize(void *data, int elemSize, int numElems, unsigned int se
 	rng_shuffleArray(&rng, data, elemSize, numElems);
 }
 
+/* ********* for threaded random ************** */
+#define MAX_RNG_THREADS		16
+
+static RNG rng_tab[MAX_RNG_THREADS];
+
+void BLI_thread_srandom(int thread, unsigned int seed)
+{
+	extern unsigned char hash[];	// noise.c
+	
+	rng_seed(&rng_tab[thread], seed + hash[seed & 255]);
+	seed= rng_getInt(&rng_tab[thread]);
+	rng_seed(&rng_tab[thread], seed + hash[seed & 255]);
+	seed= rng_getInt(&rng_tab[thread]);
+	rng_seed(&rng_tab[thread], seed + hash[seed & 255]);
+}
+
+int BLI_thread_rand(int thread) {
+	return rng_getInt(&rng_tab[thread]);
+}
+
+float BLI_thread_frand(int thread) {
+	return rng_getFloat(&rng_tab[thread]);
+}
+