Random number generator: replace a bunch of usage of the global random number

generator with a local one. It's not thread safe and will not give repeatable
results, so in most cases it should not be used.

Also fixes #34992 where the noise texture of a displacement modifier was not
properly random in opengl animation render, because the seed got reset to a
fixed value by an unrelated function while for final render it changed each
frame.

6 files changed, 34 insertions, 13 deletions

diff --git a/source/blender/modifiers/intern/MOD_explode.c b/source/blender/modifiers/intern/MOD_explode.c
index 638f8f0ae01..f0eb113e46f 100644
--- a/source/blender/modifiers/intern/MOD_explode.c
+++ b/source/blender/modifiers/intern/MOD_explode.c
@@ -104,6 +104,7 @@ static void createFacepa(ExplodeModifierData *emd,
 	MVert *mvert = NULL;
 	ParticleData *pa;
 	KDTree *tree;
+	RNG *rng;
 	float center[3], co[3];
 	int *facepa = NULL, *vertpa = NULL, totvert = 0, totface = 0, totpart = 0;
 	int i, p, v1, v2, v3, v4 = 0;
@@ -114,7 +115,7 @@ static void createFacepa(ExplodeModifierData *emd,
 	totvert = dm->getNumVerts(dm);
 	totpart = psmd->psys->totpart;
 
-	BLI_srandom(psys->seed);
+	rng = BLI_rng_new_srandom(psys->seed);
 
 	if (emd->facepa)
 		MEM_freeN(emd->facepa);
@@ -136,7 +137,7 @@ static void createFacepa(ExplodeModifierData *emd,
 		if (dvert) {
 			const int defgrp_index = emd->vgroup - 1;
 			for (i = 0; i < totvert; i++, dvert++) {
-				float val = BLI_frand();
+				float val = BLI_rng_get_float(rng);
 				val = (1.0f - emd->protect) * val + emd->protect * 0.5f;
 				if (val < defvert_find_weight(dvert, defgrp_index))
 					vertpa[i] = -1;
@@ -182,6 +183,8 @@ static void createFacepa(ExplodeModifierData *emd,
 
 	if (vertpa) MEM_freeN(vertpa);
 	BLI_kdtree_free(tree);
+
+	BLI_rng_free(rng);
 }
 
 static int edgecut_get(EdgeHash *edgehash, unsigned int v1, unsigned int v2)
diff --git a/source/blender/modifiers/intern/MOD_particleinstance.c b/source/blender/modifiers/intern/MOD_particleinstance.c
index 63dcb5d942d..8a6a83b65b2 100644
--- a/source/blender/modifiers/intern/MOD_particleinstance.c
+++ b/source/blender/modifiers/intern/MOD_particleinstance.c
@@ -313,8 +313,7 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob,
 			{
 				float ran = 0.0f;
 				if (pimd->random_position != 0.0f) {
-					BLI_srandom(psys->seed + p);
-					ran = pimd->random_position * BLI_frand();
+					ran = pimd->random_position * BLI_hash_frand(psys->seed + p);
 				}
 
 				if (pimd->flag & eParticleInstanceFlag_KeepShape) {
diff --git a/source/blender/modifiers/intern/MOD_weightvg_util.c b/source/blender/modifiers/intern/MOD_weightvg_util.c
index 7181b5bbb44..a5e63a7832f 100644
--- a/source/blender/modifiers/intern/MOD_weightvg_util.c
+++ b/source/blender/modifiers/intern/MOD_weightvg_util.c
@@ -59,7 +59,7 @@
  * vertex index (in case the weight tables do not cover the whole vertices...).
  * cmap might be NULL, in which case curve mapping mode will return unmodified data.
  */
-void weightvg_do_map(int num, float *new_w, short falloff_type, CurveMapping *cmap)
+void weightvg_do_map(int num, float *new_w, short falloff_type, CurveMapping *cmap, RNG *rng)
 {
 	int i;
 
@@ -100,8 +100,7 @@ void weightvg_do_map(int num, float *new_w, short falloff_type, CurveMapping *cm
 				fac = (float)sqrt(2 * fac - fac * fac);
 				break;
 			case MOD_WVG_MAPPING_RANDOM:
-				BLI_srand(BLI_rand()); /* random seed */
-				fac = BLI_frand() * fac;
+				fac = BLI_rng_get_float(rng) * fac;
 				break;
 			case MOD_WVG_MAPPING_STEP:
 				fac = (fac >= 0.5f) ? 1.0f : 0.0f;
diff --git a/source/blender/modifiers/intern/MOD_weightvg_util.h b/source/blender/modifiers/intern/MOD_weightvg_util.h
index 209b784d573..c7509a937b6 100644
--- a/source/blender/modifiers/intern/MOD_weightvg_util.h
+++ b/source/blender/modifiers/intern/MOD_weightvg_util.h
@@ -32,6 +32,8 @@
 #ifndef __MOD_WEIGHTVG_UTIL_H__
 #define __MOD_WEIGHTVG_UTIL_H__
 
+#include "BLI_rand.h"
+
 /* so modifier types match their defines */
 #include "MOD_modifiertypes.h"
 
@@ -65,7 +67,7 @@ struct Scene;
  * vertex index (in case the weight tables do not cover the whole vertices...).
  * cmap might be NULL, in which case curve mapping mode will return unmodified data.
  */
-void weightvg_do_map(int num, float *new_w, short mode, struct CurveMapping *cmap);
+void weightvg_do_map(int num, float *new_w, short mode, struct CurveMapping *cmap, RNG *rng);
 
 /* Applies new_w weights to org_w ones, using either a texture, vgroup or constant value as factor.
  * Return values are in org_w.
diff --git a/source/blender/modifiers/intern/MOD_weightvgedit.c b/source/blender/modifiers/intern/MOD_weightvgedit.c
index 779ac6b5ecf..dd84dce05c2 100644
--- a/source/blender/modifiers/intern/MOD_weightvgedit.c
+++ b/source/blender/modifiers/intern/MOD_weightvgedit.c
@@ -29,6 +29,7 @@
  */
 
 #include "BLI_utildefines.h"
+#include "BLI_ghash.h"
 #include "BLI_math.h"
 #include "BLI_string.h"
 
@@ -239,7 +240,15 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob, DerivedMesh *der
 
 	/* Do mapping. */
 	if (wmd->falloff_type != MOD_WVG_MAPPING_NONE) {
-		weightvg_do_map(numVerts, new_w, wmd->falloff_type, wmd->cmap_curve);
+		RNG *rng = NULL;
+
+		if (wmd->falloff_type == MOD_WVG_MAPPING_RANDOM)
+			rng = BLI_rng_new_srandom(BLI_ghashutil_strhash(ob->id.name));
+
+		weightvg_do_map(numVerts, new_w, wmd->falloff_type, wmd->cmap_curve, rng);
+
+		if (rng)
+			BLI_rng_free(rng);
 	}
 
 	/* Do masking. */
diff --git a/source/blender/modifiers/intern/MOD_weightvgproximity.c b/source/blender/modifiers/intern/MOD_weightvgproximity.c
index 71d6d4880ad..9a6b46f81b8 100644
--- a/source/blender/modifiers/intern/MOD_weightvgproximity.c
+++ b/source/blender/modifiers/intern/MOD_weightvgproximity.c
@@ -30,9 +30,10 @@
 
 #define DO_PROFILE 0
 
+#include "BLI_utildefines.h"
+#include "BLI_ghash.h"
 #include "BLI_math.h"
 #include "BLI_string.h"
-#include "BLI_utildefines.h"
 
 #if DO_PROFILE
 	#include "PIL_time.h"
@@ -185,7 +186,7 @@ static float get_ob2ob_distance(const Object *ob, const Object *obr)
 /**
  * Maps distances to weights, with an optional "smoothing" mapping.
  */
-static void do_map(float *weights, const int nidx, const float min_d, const float max_d, short mode)
+static void do_map(Object *ob, float *weights, const int nidx, const float min_d, const float max_d, short mode)
 {
 	const float range_inv = 1.0f / (max_d - min_d); /* invert since multiplication is faster */
 	unsigned int i = nidx;
@@ -210,7 +211,15 @@ static void do_map(float *weights, const int nidx, const float min_d, const floa
 	}
 
 	if (!ELEM(mode, MOD_WVG_MAPPING_NONE, MOD_WVG_MAPPING_CURVE)) {
-		weightvg_do_map(nidx, weights, mode, NULL);
+		RNG *rng = NULL;
+
+		if (mode == MOD_WVG_MAPPING_RANDOM)
+			rng = BLI_rng_new_srandom(BLI_ghashutil_strhash(ob->id.name));
+
+		weightvg_do_map(nidx, weights, mode, NULL, rng);
+
+		if (rng)
+			BLI_rng_free(rng);
 	}
 }
 
@@ -500,7 +509,7 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob, DerivedMesh *der
 	}
 
 	/* Map distances to weights. */
-	do_map(new_w, numIdx, wmd->min_dist, wmd->max_dist, wmd->falloff_type);
+	do_map(ob, new_w, numIdx, wmd->min_dist, wmd->max_dist, wmd->falloff_type);
 
 	/* Do masking. */
 	weightvg_do_mask(numIdx, indices, org_w, new_w, ob, dm, wmd->mask_constant,