diff --git a/libs/video/renderer/gl/gl_dyn_part.c b/libs/video/renderer/gl/gl_dyn_part.c
index f8e3ab923..949e8b0a3 100644
--- a/libs/video/renderer/gl/gl_dyn_part.c
+++ b/libs/video/renderer/gl/gl_dyn_part.c
@@ -42,6 +42,7 @@
 
 #include "QF/cmd.h"
 #include "QF/cvar.h"
+#include "QF/mersenne.h"
 #include "QF/qargs.h"
 #include "QF/quakefs.h"
 #include "QF/render.h"
@@ -66,6 +67,7 @@ static int						pVAsize;
 static int					   *pVAindices;
 static varray_t2f_c4ub_v3f_t   *particleVertexArray;
 
+static mtstate_t mt;	// private PRNG state
 
 inline static void
 particle_new (ptype_t type, int texnum, const vec3_t org, float scale,
@@ -110,14 +112,14 @@ particle_new_random (ptype_t type, int texnum, const vec3_t org, int org_fuzz,
 	int         rnd;
 	vec3_t      porg, pvel;
 
-	rnd = rand ();
+	rnd = mtwist_rand (&mt);
 	porg[0] = o_fuzz * ((rnd & 63) - 31.5) / 63.0 + org[0];
-	porg[1] = o_fuzz * (((rnd >> 5) & 63) - 31.5) / 63.0 + org[1];
-	porg[2] = o_fuzz * (((rnd >> 9) & 63) - 31.5) / 63.0 + org[2];
-	rnd = rand ();
+	porg[1] = o_fuzz * (((rnd >> 6) & 63) - 31.5) / 63.0 + org[1];
+	porg[2] = o_fuzz * (((rnd >> 10) & 63) - 31.5) / 63.0 + org[2];
+	rnd = mtwist_rand (&mt);
 	pvel[0] = v_fuzz * ((rnd & 63) - 31.5) / 63.0;
-	pvel[1] = v_fuzz * (((rnd >> 5) & 63) - 31.5) / 63.0;
-	pvel[2] = v_fuzz * (((rnd >> 9) & 63) - 31.5) / 63.0;
+	pvel[1] = v_fuzz * (((rnd >> 6) & 63) - 31.5) / 63.0;
+	pvel[2] = v_fuzz * (((rnd >> 10) & 63) - 31.5) / 63.0;
 
 	particle_new (type, texnum, porg, scale, pvel, die, color, alpha, ramp);
 }
@@ -151,6 +153,8 @@ gl_R_InitParticles (void)
 {
 	int		i;
 
+	mtwist_seed (&mt, 0xdeadbeef);
+
 	if (r_maxparticles && r_init) {
 		if (vaelements) {
 			partUseVA = 0;
@@ -245,7 +249,7 @@ R_ParticleExplosion_QF (const vec3_t org)
 	if (numparticles >= r_maxparticles)
 		return;
 	particle_new_random (pt_smokecloud, part_tex_smoke, org, 4, 30, 8,
-						 vr_data.realtime + 5.0, (rand () & 7) + 8,
+						 vr_data.realtime + 5.0, (mtwist_rand (&mt) & 7) + 8,
 						 0.5 + qfrandom (0.25), 0.0);
 }
 
@@ -279,12 +283,12 @@ R_BlobExplosion_QF (const vec3_t org)
 
 	for (i = 0; i < j >> 1; i++) {
 		particle_new_random (pt_blob, part_tex_dot, org, 12, 2, 256,
-							 vr_data.realtime + 1.0 + (rand () & 7) * 0.05,
+							 vr_data.realtime + 1.0 + (mtwist_rand (&mt) & 7) * 0.05,
 							 66 + i % 6, 1.0, 0.0);
 	}
 	for (i = 0; i < j / 2; i++) {
 		particle_new_random (pt_blob2, part_tex_dot, org, 12, 2, 256,
-							 vr_data.realtime + 1.0 + (rand () & 7) * 0.05,
+							 vr_data.realtime + 1.0 + (mtwist_rand (&mt) & 7) * 0.05,
 							 150 + i % 6, 1.0, 0.0);
 	}
 }
@@ -295,7 +299,7 @@ R_RunSparkEffect_QF (const vec3_t org, int count, int ofuzz)
 	if (numparticles >= r_maxparticles)
 		return;
 	particle_new (pt_smokecloud, part_tex_smoke, org, ofuzz * 0.08,
-				  vec3_origin, vr_data.realtime + 9, 12 + (rand () & 3),
+				  vec3_origin, vr_data.realtime + 9, 12 + (mtwist_rand (&mt) & 3),
 				  0.25 + qfrandom (0.125), 0.0);
 
 	if (numparticles + count >= r_maxparticles)
@@ -306,7 +310,7 @@ R_RunSparkEffect_QF (const vec3_t org, int count, int ofuzz)
 			orgfuzz = 1;
 
 		while (count--) {
-			int		color = rand () & 7;
+			int		color = mtwist_rand (&mt) & 7;
 
 			particle_new_random (pt_fallfadespark, part_tex_dot, org, orgfuzz,
 								 0.7, 96, vr_data.realtime + 5.0, ramp1[color],
@@ -322,7 +326,7 @@ R_BloodPuff_QF (const vec3_t org, int count)
 		return;
 
 	particle_new (pt_bloodcloud, part_tex_smoke, org, count / 5, vec3_origin,
-				  vr_data.realtime + 99.0, 70 + (rand () & 3), 0.5, 0.0);
+				  vr_data.realtime + 99.0, 70 + (mtwist_rand (&mt) & 3), 0.5, 0.0);
 }
 
 static void
@@ -350,7 +354,7 @@ R_LightningBloodEffect_QF (const vec3_t org)
 	if (numparticles >= r_maxparticles)
 		return;
 	particle_new (pt_smokecloud, part_tex_smoke, org, 3.0, vec3_origin,
-				  vr_data.realtime + 9.0, 12 + (rand () & 3),
+				  vr_data.realtime + 9.0, 12 + (mtwist_rand (&mt) & 3),
 				  0.25 + qfrandom (0.125), 0.0);
 
 	if (numparticles + count >= r_maxparticles)
@@ -378,7 +382,7 @@ R_RunParticleEffect_QF (const vec3_t org, const vec3_t dir, int color,
 		count = r_maxparticles - numparticles;
 
 	for (i = 0; i < count; i++) {
-		int 	rnd = rand ();
+		int 	rnd = mtwist_rand (&mt);
 
 		porg[0] = org[0] + scale * (((rnd >> 3) & 15) - 7.5);
 		porg[1] = org[1] + scale * (((rnd >> 7) & 15) - 7.5);
@@ -453,7 +457,7 @@ R_LavaSplash_QF (const vec3_t org)
 	dir[2] = 256;
 	for (i = -128; i < 128; i += 16) {
 		for (j = -128; j < 128; j += 16) {
-			rnd = rand ();
+			rnd = mtwist_rand (&mt);
 			dir[0] = j + (rnd & 7);
 			dir[1] = i + ((rnd >> 6) & 7);
 
@@ -462,7 +466,7 @@ R_LavaSplash_QF (const vec3_t org)
 			porg[2] = org[2] + ((rnd >> 9) & 63);
 
 			VectorNormalize (dir);
-			rnd = rand ();
+			rnd = mtwist_rand (&mt);
 			vel = 50.0 + 0.5 * (float) (rnd & 127);
 			VectorScale (dir, vel, pvel);
 			particle_new (pt_grav, part_tex_dot, porg, 3, pvel,
@@ -496,7 +500,7 @@ R_TeleportSplash_QF (const vec3_t org)
 				VectorCopy (dir, pdir);
 				VectorNormalize (pdir);
 
-				rnd = rand ();
+				rnd = mtwist_rand (&mt);
 				porg[0] = org[0] + i + (rnd & 3);
 				porg[1] = org[1] + j + ((rnd >> 2) & 3);
 				porg[2] = org[2] + k + ((rnd >> 4) & 3);
@@ -504,7 +508,7 @@ R_TeleportSplash_QF (const vec3_t org)
 				vel = 50 + ((rnd >> 6) & 63);
 				VectorScale (pdir, vel, pvel);
 				particle_new (pt_grav, part_tex_spark, porg, 0.6, pvel,
-							  (vr_data.realtime + 0.2 + (rand () & 15) * 0.01),
+							  (vr_data.realtime + 0.2 + (mtwist_rand (&mt) & 15) * 0.01),
 							  (7 + ((rnd >> 12) & 7)), 1.0, 0.0);
 			}
 		}
@@ -535,7 +539,7 @@ R_RocketTrail_QF (const entity_t *ent)
 		particle_new (pt_smoke, part_tex_smoke, old_origin,
 					  pscale + percent * 4.0, vec3_origin,
 					  vr_data.realtime + 2.0 - percent * 2.0,
-					  12 + (rand () & 3),
+					  12 + (mtwist_rand (&mt) & 3),
 					  0.5 + qfrandom (0.125) - percent * 0.40, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
@@ -569,7 +573,7 @@ R_GrenadeTrail_QF (const entity_t *ent)
 		particle_new (pt_smoke, part_tex_smoke, old_origin,
 					  pscale + percent * 4.0, vec3_origin,
 					  vr_data.realtime + 2.0 - percent * 2.0,
-					  1 + (rand () & 3),
+					  1 + (mtwist_rand (&mt) & 3),
 					  0.625 + qfrandom (0.125) - percent * 0.40, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
@@ -610,7 +614,7 @@ R_BloodTrail_QF (const entity_t *ent)
 
 		particle_new (pt_grav, part_tex_smoke, porg, pscale, pvel,
 					  vr_data.realtime + 2.0 - percent * 2.0,
-					  68 + (rand () & 3), 1.0, 0.0);
+					  68 + (mtwist_rand (&mt) & 3), 1.0, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
 		len += dist;
@@ -650,7 +654,7 @@ R_SlightBloodTrail_QF (const entity_t *ent)
 
 		particle_new (pt_grav, part_tex_smoke, porg, pscale, pvel,
 					  vr_data.realtime + 1.5 - percent * 1.5,
-					  68 + (rand () & 3), 0.75, 0.0);
+					  68 + (mtwist_rand (&mt) & 3), 0.75, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
 		len += dist;
@@ -692,7 +696,7 @@ R_WizTrail_QF (const entity_t *ent)
 		particle_new (pt_flame, part_tex_smoke, old_origin,
 					  2.0 + qfrandom (1.0) - percent * 2.0, pvel,
 					  vr_data.realtime + 0.5 - percent * 0.5,
-					  52 + (rand () & 4), 1.0 - percent * 0.125, 0.0);
+					  52 + (mtwist_rand (&mt) & 4), 1.0 - percent * 0.125, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
 		len += dist;
@@ -766,7 +770,7 @@ R_VoorTrail_QF (const entity_t *ent)
 
 		particle_new (pt_static, part_tex_dot, porg, 1.0 + qfrandom (1.0),
 					  vec3_origin, vr_data.realtime + 0.3 - percent * 0.3,
-					  9 * 16 + 8 + (rand () & 3), 1.0, 0.0);
+					  9 * 16 + 8 + (mtwist_rand (&mt) & 3), 1.0, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
 		len += dist;
@@ -794,7 +798,7 @@ R_GlowTrail_QF (const entity_t *ent, int glow_color)
 	while (len < maxlen) {
 		percent = len * origlen;
 
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		org[0] = old_origin[0] + ((rnd >> 12) & 7) * (5.0/7.0) - 2.5;
 		org[1] = old_origin[1] + ((rnd >> 9) & 7) * (5.0/7.0) - 2.5;
 		org[2] = old_origin[2] + ((rnd >> 6) & 7) * (5.0/7.0) - 2.5;
@@ -818,7 +822,7 @@ R_ParticleExplosion_EE (const vec3_t org)
 	if (numparticles >= r_maxparticles)
 		return;
 	particle_new_random (pt_smokecloud, part_tex_smoke, org, 4, 30, 8,
-						 vr_data.realtime + 5.0, rand () & 255,
+						 vr_data.realtime + 5.0, mtwist_rand (&mt) & 255,
 						 0.5 + qfrandom (0.25), 0.0);
 }
 
@@ -843,7 +847,7 @@ R_TeleportSplash_EE (const vec3_t org)
 			for (j = -16; j < 16; j += 4) {
 				dir[0] = j * 8;
 
-				rnd = rand ();
+				rnd = mtwist_rand (&mt);
 				porg[0] = org[0] + i + (rnd & 3);
 				porg[1] = org[1] + j + ((rnd >> 2) & 3);
 				porg[2] = org[2] + k + ((rnd >> 4) & 3);
@@ -852,7 +856,7 @@ R_TeleportSplash_EE (const vec3_t org)
 				vel = 50 + ((rnd >> 6) & 63);
 				VectorScale (dir, vel, pvel);
 				particle_new (pt_grav, part_tex_spark, porg, 0.6, pvel,
-							  (vr_data.realtime + 0.2 + (rand () & 15) * 0.01),
+							  (vr_data.realtime + 0.2 + (mtwist_rand (&mt) & 15) * 0.01),
 							  qfrandom (1.0), 1.0, 0.0);
 			}
 		}
@@ -883,7 +887,7 @@ R_RocketTrail_EE (const entity_t *ent)
 		particle_new (pt_smoke, part_tex_smoke, old_origin,
 					  pscale + percent * 4.0, vec3_origin,
 					  vr_data.realtime + 2.0 - percent * 2.0,
-					  rand () & 255,
+					  mtwist_rand (&mt) & 255,
 					  0.5 + qfrandom (0.125) - percent * 0.40, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
@@ -918,7 +922,7 @@ R_GrenadeTrail_EE (const entity_t *ent)
 		particle_new (pt_smoke, part_tex_smoke, old_origin,
 					  pscale + percent * 4.0, vec3_origin,
 					  vr_data.realtime + 2.0 - percent * 2.0,
-					  rand () & 255,
+					  mtwist_rand (&mt) & 255,
 					  0.625 + qfrandom (0.125) - percent * 0.40, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
@@ -963,12 +967,12 @@ R_BlobExplosion_ID (const vec3_t org)
 
 	for (i = 0; i < j >> 1; i++) {
 		particle_new_random (pt_blob, part_tex_dot, org, 12, 1.0, 256,
-							 vr_data.realtime + 1.0 + (rand () & 8) * 0.05,
+							 vr_data.realtime + 1.0 + (mtwist_rand (&mt) & 8) * 0.05,
 							 66 + i % 6, 1.0, 0.0);
 	}
 	for (i = 0; i < j / 2; i++) {
 		particle_new_random (pt_blob2, part_tex_dot, org, 12, 1.0, 256,
-							 vr_data.realtime + 1.0 + (rand () & 8) * 0.05,
+							 vr_data.realtime + 1.0 + (mtwist_rand (&mt) & 8) * 0.05,
 							 150 + i % 6, 1.0, 0.0);
 	}
 }
@@ -995,7 +999,7 @@ R_RunParticleEffect_ID (const vec3_t org, const vec3_t dir, int color,
 		count = r_maxparticles - numparticles;
 
 	for (i = 0; i < count; i++) {
-		int rnd = rand ();
+		int rnd = mtwist_rand (&mt);
 
 		porg[0] = org[0] + scale * (((rnd >> 3) & 15) - 8);
 		porg[1] = org[1] + scale * (((rnd >> 7) & 15) - 8);
@@ -1067,7 +1071,7 @@ R_LavaSplash_ID (const vec3_t org)
 	dir[2] = 256;
 	for (i = -128; i < 128; i += 16) {
 		for (j = -128; j < 128; j += 16) {
-			rnd = rand ();
+			rnd = mtwist_rand (&mt);
 			dir[0] = j + (rnd & 7);
 			dir[1] = i + ((rnd >> 6) & 7);
 
@@ -1076,7 +1080,7 @@ R_LavaSplash_ID (const vec3_t org)
 			porg[2] = org[2] + ((rnd >> 9) & 63);
 
 			VectorNormalize (dir);
-			rnd = rand ();
+			rnd = mtwist_rand (&mt);
 			vel = 50 + (rnd & 63);
 			VectorScale (dir, vel, pvel);
 			particle_new (pt_grav, part_tex_dot, porg, 1.0, pvel,
@@ -1110,7 +1114,7 @@ R_TeleportSplash_ID (const vec3_t org)
 				VectorCopy (dir, pdir);
 				VectorNormalize (pdir);
 
-				rnd = rand ();
+				rnd = mtwist_rand (&mt);
 				porg[0] = org[0] + i + (rnd & 3);
 				porg[1] = org[1] + j + ((rnd >> 2) & 3);
 				porg[2] = org[2] + k + ((rnd >> 4) & 3);
@@ -1118,7 +1122,7 @@ R_TeleportSplash_ID (const vec3_t org)
 				vel = 50 + ((rnd >> 6) & 63);
 				VectorScale (pdir, vel, pvel);
 				particle_new (pt_grav, part_tex_dot, porg, 1.0, pvel,
-							  (vr_data.realtime + 0.2 + (rand () & 7) * 0.02),
+							  (vr_data.realtime + 0.2 + (mtwist_rand (&mt) & 7) * 0.02),
 							  (7 + ((rnd >> 12) & 7)), 1.0, 0.0);
 			}
 		}
@@ -1147,7 +1151,7 @@ R_DarkFieldParticles_ID (const entity_t *ent)
 			dir [0] = j * 8;
 			for (k = 0; k < 32; k += 8) {
 				dir [2] = k * 8;
-				rnd = rand ();
+				rnd = mtwist_rand (&mt);
 
 				porg[0] = org[0] + i + ((rnd >> 3) & 3);
 				porg[1] = org[1] + j + ((rnd >> 5) & 3);
@@ -1158,7 +1162,7 @@ R_DarkFieldParticles_ID (const entity_t *ent)
 				VectorScale (dir, vel, pvel);
 				particle_new (pt_slowgrav, part_tex_dot, porg, 1.5, pvel,
 							  (vr_data.realtime + 0.2 + (rnd & 7) * 0.02),
-							  (150 + rand () % 6), 1.0, 0.0);
+							  (150 + mtwist_rand (&mt) % 6), 1.0, 0.0);
             }
 		}
 	}
@@ -1182,7 +1186,7 @@ R_EntityParticles_ID (const entity_t *ent)
 
 	if (!avelocities[0][0]) {
 		for (i = 0; i < NUMVERTEXNORMALS * 3; i++)
-			avelocities[0][i] = (rand () & 255) * 0.01;
+			avelocities[0][i] = (mtwist_rand (&mt) & 255) * 0.01;
 	}
 
 	for (i = 0; i < j; i++) {
@@ -1229,7 +1233,7 @@ R_RocketTrail_ID (const entity_t *ent)
 	VectorScale (vec, (maxlen - dist), subtract);
 
 	while (len < maxlen) {
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		org[0] = old_origin[0] + ((rnd >> 12) & 7) * (5.0/7.0) - 2.5;
 		org[1] = old_origin[1] + ((rnd >> 9) & 7) * (5.0/7.0) - 2.5;
 		org[2] = old_origin[2] + ((rnd >> 6) & 7) * (5.0/7.0) - 2.5;
@@ -1261,7 +1265,7 @@ R_GrenadeTrail_ID (const entity_t *ent)
 	VectorScale (vec, maxlen - dist, subtract);
 
 	while (len < maxlen) {
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		org[0] = old_origin[0] + ((rnd >> 12) & 7) * (5.0/7.0) - 2.5;
 		org[1] = old_origin[1] + ((rnd >> 9) & 7) * (5.0/7.0) - 2.5;
 		org[2] = old_origin[2] + ((rnd >> 6) & 7) * (5.0/7.0) - 2.5;
@@ -1293,7 +1297,7 @@ R_BloodTrail_ID (const entity_t *ent)
 	VectorScale (vec, maxlen - dist, subtract);
 
 	while (len < maxlen) {
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		porg[0] = old_origin[0] + ((rnd >> 12) & 7) * (5.0/7.0) - 2.5;
 		porg[1] = old_origin[1] + ((rnd >> 9) & 7) * (5.0/7.0) - 2.5;
 		porg[2] = old_origin[2] + ((rnd >> 6) & 7) * (5.0/7.0) - 2.5;
@@ -1324,7 +1328,7 @@ R_SlightBloodTrail_ID (const entity_t *ent)
 	VectorScale (vec, maxlen - dist, subtract);
 
 	while (len < maxlen) {
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		porg[0] = old_origin[0] + ((rnd >> 12) & 7) * (5.0/7.0) - 2.5;
 		porg[1] = old_origin[1] + ((rnd >> 9) & 7) * (5.0/7.0) - 2.5;
 		porg[2] = old_origin[2] + ((rnd >> 6) & 7) * (5.0/7.0) - 2.5;
@@ -1429,7 +1433,7 @@ R_VoorTrail_ID (const entity_t *ent)
 	VectorScale (vec, maxlen - dist, subtract);
 
 	while (len < maxlen) {
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		porg[0] = old_origin[0] + ((rnd >> 3) & 15) - 7.5;
 		porg[1] = old_origin[1] + ((rnd >> 7) & 15) - 7.5;
 		porg[2] = old_origin[2] + ((rnd >> 11) & 15) - 7.5;
diff --git a/libs/video/renderer/glsl/glsl_particles.c b/libs/video/renderer/glsl/glsl_particles.c
index a74e8d2c9..06ca3d000 100644
--- a/libs/video/renderer/glsl/glsl_particles.c
+++ b/libs/video/renderer/glsl/glsl_particles.c
@@ -43,6 +43,7 @@
 #include "QF/cmd.h"
 #include "QF/cvar.h"
 #include "QF/image.h"
+#include "QF/mersenne.h"
 #include "QF/qargs.h"
 #include "QF/quakefs.h"
 #include "QF/render.h"
@@ -57,6 +58,8 @@
 
 #include "r_internal.h"
 
+static mtstate_t mt;	// private PRNG state
+
 //FIXME not part of GLES, but needed for GL
 #ifndef GL_VERTEX_PROGRAM_POINT_SIZE
 # define GL_VERTEX_PROGRAM_POINT_SIZE 0x8642
@@ -168,14 +171,14 @@ particle_new_random (ptype_t type, int texnum, const vec3_t org, int org_fuzz,
 	int         rnd;
 	vec3_t      porg, pvel;
 
-	rnd = rand ();
+	rnd = mtwist_rand (&mt);
 	porg[0] = o_fuzz * ((rnd & 63) - 31.5) / 63.0 + org[0];
-	porg[1] = o_fuzz * (((rnd >> 5) & 63) - 31.5) / 63.0 + org[1];
-	porg[2] = o_fuzz * (((rnd >> 9) & 63) - 31.5) / 63.0 + org[2];
-	rnd = rand ();
+	porg[1] = o_fuzz * (((rnd >> 6) & 63) - 31.5) / 63.0 + org[1];
+	porg[2] = o_fuzz * (((rnd >> 10) & 63) - 31.5) / 63.0 + org[2];
+	rnd = mtwist_rand (&mt);
 	pvel[0] = v_fuzz * ((rnd & 63) - 31.5) / 63.0;
-	pvel[1] = v_fuzz * (((rnd >> 5) & 63) - 31.5) / 63.0;
-	pvel[2] = v_fuzz * (((rnd >> 9) & 63) - 31.5) / 63.0;
+	pvel[1] = v_fuzz * (((rnd >> 6) & 63) - 31.5) / 63.0;
+	pvel[2] = v_fuzz * (((rnd >> 10) & 63) - 31.5) / 63.0;
 
 	particle_new (type, texnum, porg, scale, pvel, die, color, alpha, ramp);
 }
@@ -214,6 +217,8 @@ glsl_R_InitParticles (void)
 	byte        data[64][64][2];
 	tex_t      *tex;
 
+	mtwist_seed (&mt, 0xdeadbeef);
+
 	qfeglEnable (GL_VERTEX_PROGRAM_POINT_SIZE);
 	qfeglGetFloatv (GL_ALIASED_POINT_SIZE_RANGE, v);
 	Sys_MaskPrintf (SYS_GLSL, "point size: %g - %g\n", v[0], v[1]);
@@ -331,7 +336,7 @@ R_ParticleExplosion_QF (const vec3_t org)
 	if (numparticles >= r_maxparticles)
 		return;
 	particle_new_random (pt_smokecloud, part_tex_smoke, org, 4, 30, 8,
-						 vr_data.realtime + 5.0, (rand () & 7) + 8,
+						 vr_data.realtime + 5.0, (mtwist_rand (&mt) & 7) + 8,
 						 0.5 + qfrandom (0.25), 0.0);
 }
 
@@ -365,12 +370,12 @@ R_BlobExplosion_QF (const vec3_t org)
 
 	for (i = 0; i < j >> 1; i++) {
 		particle_new_random (pt_blob, part_tex_dot, org, 12, 2, 256,
-							 vr_data.realtime + 1.0 + (rand () & 7) * 0.05,
+							 vr_data.realtime + 1.0 + (mtwist_rand (&mt) & 7) * 0.05,
 							 66 + i % 6, 1.0, 0.0);
 	}
 	for (i = 0; i < j / 2; i++) {
 		particle_new_random (pt_blob2, part_tex_dot, org, 12, 2, 256,
-							 vr_data.realtime + 1.0 + (rand () & 7) * 0.05,
+							 vr_data.realtime + 1.0 + (mtwist_rand (&mt) & 7) * 0.05,
 							 150 + i % 6, 1.0, 0.0);
 	}
 }
@@ -381,7 +386,7 @@ R_RunSparkEffect_QF (const vec3_t org, int count, int ofuzz)
 	if (numparticles >= r_maxparticles)
 		return;
 	particle_new (pt_smokecloud, part_tex_smoke, org, ofuzz * 0.08,
-				  vec3_origin, vr_data.realtime + 9, 12 + (rand () & 3),
+				  vec3_origin, vr_data.realtime + 9, 12 + (mtwist_rand (&mt) & 3),
 				  0.25 + qfrandom (0.125), 0.0);
 
 	if (numparticles + count >= r_maxparticles)
@@ -392,7 +397,7 @@ R_RunSparkEffect_QF (const vec3_t org, int count, int ofuzz)
 			orgfuzz = 1;
 
 		while (count--) {
-			int		color = rand () & 7;
+			int		color = mtwist_rand (&mt) & 7;
 
 			particle_new_random (pt_fallfadespark, part_tex_dot, org, orgfuzz,
 								 0.7, 96, vr_data.realtime + 5.0, ramp1[color],
@@ -408,7 +413,7 @@ R_BloodPuff_QF (const vec3_t org, int count)
 		return;
 
 	particle_new (pt_bloodcloud, part_tex_smoke, org, count / 5, vec3_origin,
-				  vr_data.realtime + 99.0, 70 + (rand () & 3), 0.5, 0.0);
+				  vr_data.realtime + 99.0, 70 + (mtwist_rand (&mt) & 3), 0.5, 0.0);
 }
 
 static void
@@ -436,7 +441,7 @@ R_LightningBloodEffect_QF (const vec3_t org)
 	if (numparticles >= r_maxparticles)
 		return;
 	particle_new (pt_smokecloud, part_tex_smoke, org, 3.0, vec3_origin,
-				  vr_data.realtime + 9.0, 12 + (rand () & 3),
+				  vr_data.realtime + 9.0, 12 + (mtwist_rand (&mt) & 3),
 				  0.25 + qfrandom (0.125), 0.0);
 
 	if (numparticles + count >= r_maxparticles)
@@ -464,7 +469,7 @@ R_RunParticleEffect_QF (const vec3_t org, const vec3_t dir, int color,
 		count = r_maxparticles - numparticles;
 
 	for (i = 0; i < count; i++) {
-		int 	rnd = rand ();
+		int 	rnd = mtwist_rand (&mt);
 
 		porg[0] = org[0] + scale * (((rnd >> 3) & 15) - 7.5);
 		porg[1] = org[1] + scale * (((rnd >> 7) & 15) - 7.5);
@@ -539,7 +544,7 @@ R_LavaSplash_QF (const vec3_t org)
 	dir[2] = 256;
 	for (i = -128; i < 128; i += 16) {
 		for (j = -128; j < 128; j += 16) {
-			rnd = rand ();
+			rnd = mtwist_rand (&mt);
 			dir[0] = j + (rnd & 7);
 			dir[1] = i + ((rnd >> 6) & 7);
 
@@ -548,7 +553,7 @@ R_LavaSplash_QF (const vec3_t org)
 			porg[2] = org[2] + ((rnd >> 9) & 63);
 
 			VectorNormalize (dir);
-			rnd = rand ();
+			rnd = mtwist_rand (&mt);
 			vel = 50.0 + 0.5 * (float) (rnd & 127);
 			VectorScale (dir, vel, pvel);
 			particle_new (pt_grav, part_tex_dot, porg, 3, pvel,
@@ -582,7 +587,7 @@ R_TeleportSplash_QF (const vec3_t org)
 				VectorCopy (dir, pdir);
 				VectorNormalize (pdir);
 
-				rnd = rand ();
+				rnd = mtwist_rand (&mt);
 				porg[0] = org[0] + i + (rnd & 3);
 				porg[1] = org[1] + j + ((rnd >> 2) & 3);
 				porg[2] = org[2] + k + ((rnd >> 4) & 3);
@@ -590,7 +595,7 @@ R_TeleportSplash_QF (const vec3_t org)
 				vel = 50 + ((rnd >> 6) & 63);
 				VectorScale (pdir, vel, pvel);
 				particle_new (pt_grav, part_tex_spark, porg, 0.6, pvel,
-							  (vr_data.realtime + 0.2 + (rand () & 15) * 0.01),
+							  (vr_data.realtime + 0.2 + (mtwist_rand (&mt) & 15) * 0.01),
 							  (7 + ((rnd >> 12) & 7)), 1.0, 0.0);
 			}
 		}
@@ -621,7 +626,7 @@ R_RocketTrail_QF (const entity_t *ent)
 		particle_new (pt_smoke, part_tex_smoke, old_origin,
 					  pscale + percent * 4.0, vec3_origin,
 					  vr_data.realtime + 2.0 - percent * 2.0,
-					  12 + (rand () & 3),
+					  12 + (mtwist_rand (&mt) & 3),
 					  0.5 + qfrandom (0.125) - percent * 0.40, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
@@ -655,7 +660,7 @@ R_GrenadeTrail_QF (const entity_t *ent)
 		particle_new (pt_smoke, part_tex_smoke, old_origin,
 					  pscale + percent * 4.0, vec3_origin,
 					  vr_data.realtime + 2.0 - percent * 2.0,
-					  1 + (rand () & 3),
+					  1 + (mtwist_rand (&mt) & 3),
 					  0.625 + qfrandom (0.125) - percent * 0.40, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
@@ -696,7 +701,7 @@ R_BloodTrail_QF (const entity_t *ent)
 
 		particle_new (pt_grav, part_tex_smoke, porg, pscale, pvel,
 					  vr_data.realtime + 2.0 - percent * 2.0,
-					  68 + (rand () & 3), 1.0, 0.0);
+					  68 + (mtwist_rand (&mt) & 3), 1.0, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
 		len += dist;
@@ -736,7 +741,7 @@ R_SlightBloodTrail_QF (const entity_t *ent)
 
 		particle_new (pt_grav, part_tex_smoke, porg, pscale, pvel,
 					  vr_data.realtime + 1.5 - percent * 1.5,
-					  68 + (rand () & 3), 0.75, 0.0);
+					  68 + (mtwist_rand (&mt) & 3), 0.75, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
 		len += dist;
@@ -778,7 +783,7 @@ R_WizTrail_QF (const entity_t *ent)
 		particle_new (pt_flame, part_tex_smoke, old_origin,
 					  2.0 + qfrandom (1.0) - percent * 2.0, pvel,
 					  vr_data.realtime + 0.5 - percent * 0.5,
-					  52 + (rand () & 4), 1.0 - percent * 0.125, 0.0);
+					  52 + (mtwist_rand (&mt) & 4), 1.0 - percent * 0.125, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
 		len += dist;
@@ -852,7 +857,7 @@ R_VoorTrail_QF (const entity_t *ent)
 
 		particle_new (pt_static, part_tex_dot, porg, 1.0 + qfrandom (1.0),
 					  vec3_origin, vr_data.realtime + 0.3 - percent * 0.3,
-					  9 * 16 + 8 + (rand () & 3), 1.0, 0.0);
+					  9 * 16 + 8 + (mtwist_rand (&mt) & 3), 1.0, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
 		len += dist;
@@ -880,7 +885,7 @@ R_GlowTrail_QF (const entity_t *ent, int glow_color)
 	while (len < maxlen) {
 		percent = len * origlen;
 
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		org[0] = old_origin[0] + ((rnd >> 12) & 7) * (5.0/7.0) - 2.5;
 		org[1] = old_origin[1] + ((rnd >> 9) & 7) * (5.0/7.0) - 2.5;
 		org[2] = old_origin[2] + ((rnd >> 6) & 7) * (5.0/7.0) - 2.5;
@@ -904,7 +909,7 @@ R_ParticleExplosion_EE (const vec3_t org)
 	if (numparticles >= r_maxparticles)
 		return;
 	particle_new_random (pt_smokecloud, part_tex_smoke, org, 4, 30, 8,
-						 vr_data.realtime + 5.0, rand () & 255,
+						 vr_data.realtime + 5.0, mtwist_rand (&mt) & 255,
 						 0.5 + qfrandom (0.25), 0.0);
 }
 
@@ -929,7 +934,7 @@ R_TeleportSplash_EE (const vec3_t org)
 			for (j = -16; j < 16; j += 4) {
 				dir[0] = j * 8;
 
-				rnd = rand ();
+				rnd = mtwist_rand (&mt);
 				porg[0] = org[0] + i + (rnd & 3);
 				porg[1] = org[1] + j + ((rnd >> 2) & 3);
 				porg[2] = org[2] + k + ((rnd >> 4) & 3);
@@ -938,7 +943,7 @@ R_TeleportSplash_EE (const vec3_t org)
 				vel = 50 + ((rnd >> 6) & 63);
 				VectorScale (dir, vel, pvel);
 				particle_new (pt_grav, part_tex_spark, porg, 0.6, pvel,
-							  (vr_data.realtime + 0.2 + (rand () & 15) * 0.01),
+							  (vr_data.realtime + 0.2 + (mtwist_rand (&mt) & 15) * 0.01),
 							  qfrandom (1.0), 1.0, 0.0);
 			}
 		}
@@ -969,7 +974,7 @@ R_RocketTrail_EE (const entity_t *ent)
 		particle_new (pt_smoke, part_tex_smoke, old_origin,
 					  pscale + percent * 4.0, vec3_origin,
 					  vr_data.realtime + 2.0 - percent * 2.0,
-					  rand () & 255,
+					  mtwist_rand (&mt) & 255,
 					  0.5 + qfrandom (0.125) - percent * 0.40, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
@@ -1004,7 +1009,7 @@ R_GrenadeTrail_EE (const entity_t *ent)
 		particle_new (pt_smoke, part_tex_smoke, old_origin,
 					  pscale + percent * 4.0, vec3_origin,
 					  vr_data.realtime + 2.0 - percent * 2.0,
-					  rand () & 255,
+					  mtwist_rand (&mt) & 255,
 					  0.625 + qfrandom (0.125) - percent * 0.40, 0.0);
 		if (numparticles >= r_maxparticles)
 			break;
@@ -1049,12 +1054,12 @@ R_BlobExplosion_ID (const vec3_t org)
 
 	for (i = 0; i < j >> 1; i++) {
 		particle_new_random (pt_blob, part_tex_dot, org, 12, 1.0, 256,
-							 vr_data.realtime + 1.0 + (rand () & 8) * 0.05,
+							 vr_data.realtime + 1.0 + (mtwist_rand (&mt) & 8) * 0.05,
 							 66 + i % 6, 1.0, 0.0);
 	}
 	for (i = 0; i < j / 2; i++) {
 		particle_new_random (pt_blob2, part_tex_dot, org, 12, 1.0, 256,
-							 vr_data.realtime + 1.0 + (rand () & 8) * 0.05,
+							 vr_data.realtime + 1.0 + (mtwist_rand (&mt) & 8) * 0.05,
 							 150 + i % 6, 1.0, 0.0);
 	}
 }
@@ -1081,7 +1086,7 @@ R_RunParticleEffect_ID (const vec3_t org, const vec3_t dir, int color,
 		count = r_maxparticles - numparticles;
 
 	for (i = 0; i < count; i++) {
-		int rnd = rand ();
+		int rnd = mtwist_rand (&mt);
 
 		porg[0] = org[0] + scale * (((rnd >> 3) & 15) - 8);
 		porg[1] = org[1] + scale * (((rnd >> 7) & 15) - 8);
@@ -1153,7 +1158,7 @@ R_LavaSplash_ID (const vec3_t org)
 	dir[2] = 256;
 	for (i = -128; i < 128; i += 16) {
 		for (j = -128; j < 128; j += 16) {
-			rnd = rand ();
+			rnd = mtwist_rand (&mt);
 			dir[0] = j + (rnd & 7);
 			dir[1] = i + ((rnd >> 6) & 7);
 
@@ -1162,7 +1167,7 @@ R_LavaSplash_ID (const vec3_t org)
 			porg[2] = org[2] + ((rnd >> 9) & 63);
 
 			VectorNormalize (dir);
-			rnd = rand ();
+			rnd = mtwist_rand (&mt);
 			vel = 50 + (rnd & 63);
 			VectorScale (dir, vel, pvel);
 			particle_new (pt_grav, part_tex_dot, porg, 1.0, pvel,
@@ -1196,7 +1201,7 @@ R_TeleportSplash_ID (const vec3_t org)
 				VectorCopy (dir, pdir);
 				VectorNormalize (pdir);
 
-				rnd = rand ();
+				rnd = mtwist_rand (&mt);
 				porg[0] = org[0] + i + (rnd & 3);
 				porg[1] = org[1] + j + ((rnd >> 2) & 3);
 				porg[2] = org[2] + k + ((rnd >> 4) & 3);
@@ -1204,7 +1209,7 @@ R_TeleportSplash_ID (const vec3_t org)
 				vel = 50 + ((rnd >> 6) & 63);
 				VectorScale (pdir, vel, pvel);
 				particle_new (pt_grav, part_tex_dot, porg, 1.0, pvel,
-							  (vr_data.realtime + 0.2 + (rand () & 7) * 0.02),
+							  (vr_data.realtime + 0.2 + (mtwist_rand (&mt) & 7) * 0.02),
 							  (7 + ((rnd >> 12) & 7)), 1.0, 0.0);
 			}
 		}
@@ -1233,7 +1238,7 @@ R_DarkFieldParticles_ID (const entity_t *ent)
 			dir [0] = j * 8;
 			for (k = 0; k < 32; k += 8) {
 				dir [2] = k * 8;
-				rnd = rand ();
+				rnd = mtwist_rand (&mt);
 
 				porg[0] = org[0] + i + ((rnd >> 3) & 3);
 				porg[1] = org[1] + j + ((rnd >> 5) & 3);
@@ -1244,7 +1249,7 @@ R_DarkFieldParticles_ID (const entity_t *ent)
 				VectorScale (dir, vel, pvel);
 				particle_new (pt_slowgrav, part_tex_dot, porg, 1.5, pvel,
 							  (vr_data.realtime + 0.2 + (rnd & 7) * 0.02),
-							  (150 + rand () % 6), 1.0, 0.0);
+							  (150 + mtwist_rand (&mt) % 6), 1.0, 0.0);
             }
 		}
 	}
@@ -1268,7 +1273,7 @@ R_EntityParticles_ID (const entity_t *ent)
 
 	if (!avelocities[0][0]) {
 		for (i = 0; i < NUMVERTEXNORMALS * 3; i++)
-			avelocities[0][i] = (rand () & 255) * 0.01;
+			avelocities[0][i] = (mtwist_rand (&mt) & 255) * 0.01;
 	}
 
 	for (i = 0; i < j; i++) {
@@ -1315,7 +1320,7 @@ R_RocketTrail_ID (const entity_t *ent)
 	VectorScale (vec, (maxlen - dist), subtract);
 
 	while (len < maxlen) {
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		org[0] = old_origin[0] + ((rnd >> 12) & 7) * (5.0/7.0) - 2.5;
 		org[1] = old_origin[1] + ((rnd >> 9) & 7) * (5.0/7.0) - 2.5;
 		org[2] = old_origin[2] + ((rnd >> 6) & 7) * (5.0/7.0) - 2.5;
@@ -1347,7 +1352,7 @@ R_GrenadeTrail_ID (const entity_t *ent)
 	VectorScale (vec, maxlen - dist, subtract);
 
 	while (len < maxlen) {
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		org[0] = old_origin[0] + ((rnd >> 12) & 7) * (5.0/7.0) - 2.5;
 		org[1] = old_origin[1] + ((rnd >> 9) & 7) * (5.0/7.0) - 2.5;
 		org[2] = old_origin[2] + ((rnd >> 6) & 7) * (5.0/7.0) - 2.5;
@@ -1379,7 +1384,7 @@ R_BloodTrail_ID (const entity_t *ent)
 	VectorScale (vec, maxlen - dist, subtract);
 
 	while (len < maxlen) {
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		porg[0] = old_origin[0] + ((rnd >> 12) & 7) * (5.0/7.0) - 2.5;
 		porg[1] = old_origin[1] + ((rnd >> 9) & 7) * (5.0/7.0) - 2.5;
 		porg[2] = old_origin[2] + ((rnd >> 6) & 7) * (5.0/7.0) - 2.5;
@@ -1410,7 +1415,7 @@ R_SlightBloodTrail_ID (const entity_t *ent)
 	VectorScale (vec, maxlen - dist, subtract);
 
 	while (len < maxlen) {
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		porg[0] = old_origin[0] + ((rnd >> 12) & 7) * (5.0/7.0) - 2.5;
 		porg[1] = old_origin[1] + ((rnd >> 9) & 7) * (5.0/7.0) - 2.5;
 		porg[2] = old_origin[2] + ((rnd >> 6) & 7) * (5.0/7.0) - 2.5;
@@ -1515,7 +1520,7 @@ R_VoorTrail_ID (const entity_t *ent)
 	VectorScale (vec, maxlen - dist, subtract);
 
 	while (len < maxlen) {
-		rnd = rand ();
+		rnd = mtwist_rand (&mt);
 		porg[0] = old_origin[0] + ((rnd >> 3) & 15) - 7.5;
 		porg[1] = old_origin[1] + ((rnd >> 7) & 15) - 7.5;
 		porg[2] = old_origin[2] + ((rnd >> 11) & 15) - 7.5;
diff --git a/libs/video/renderer/sw/sw_rpart.c b/libs/video/renderer/sw/sw_rpart.c
index 708c1181d..b198624ee 100644
--- a/libs/video/renderer/sw/sw_rpart.c
+++ b/libs/video/renderer/sw/sw_rpart.c
@@ -37,6 +37,7 @@
 #endif
 
 #include "QF/cvar.h"
+#include "QF/mersenne.h"
 #include "QF/qargs.h"
 #include "QF/quakefs.h"
 #include "QF/render.h"
@@ -50,10 +51,12 @@ static int		ramp1[8] = { 0x6f, 0x6d, 0x6b, 0x69, 0x67, 0x65, 0x63, 0x61 };
 //static int	ramp2[8] = { 0x6f, 0x6e, 0x6d, 0x6c, 0x6b, 0x6a, 0x68, 0x66 };
 static int		ramp3[8] = { 0x6d, 0x6b, 6, 5, 4, 3 };
 
+static mtstate_t mt;	// private PRNG state
 
 void
 R_InitParticles (void)
 {
+	mtwist_seed (&mt, 0xdeadbeef);
 }
 
 void
@@ -145,15 +148,15 @@ R_ParticleExplosion_QF (const vec3_t org)
 
 		p->die = vr_data.realtime + 5;
 		p->color = ramp1[0];
-		p->ramp = rand () & 3;
+		p->ramp = mtwist_rand (&mt) & 3;
 		if (i & 1)
 			p->type = pt_explode;
 		else
 			p->type = pt_explode2;
 		p->phys = R_ParticlePhysics (p->type);
 		for (j = 0; j < 3; j++) {
-			p->org[j] = org[j] + ((rand () % 32) - 16);
-			p->vel[j] = (rand () % 512) - 256;
+			p->org[j] = org[j] + ((mtwist_rand (&mt) % 32) - 16);
+			p->vel[j] = (mtwist_rand (&mt) % 512) - 256;
 		}
 	}
 }
@@ -180,8 +183,8 @@ R_ParticleExplosion2_QF (const vec3_t org, int colorStart, int colorLength)
 		p->type = pt_blob;
 		p->phys = R_ParticlePhysics (p->type);
 		for (j=0 ; j<3 ; j++) {
-			p->org[j] = org[j] + ((rand()%32)-16);
-			p->vel[j] = (rand()%512)-256;
+			p->org[j] = org[j] + ((mtwist_rand (&mt)%32)-16);
+			p->vel[j] = (mtwist_rand (&mt)%512)-256;
 		}
 	}
 }
@@ -203,19 +206,19 @@ R_BlobExplosion_QF (const vec3_t org)
 		p->next = active_particles;
 		active_particles = p;
 
-		p->die = vr_data.realtime + 1 + (rand () & 8) * 0.05;
+		p->die = vr_data.realtime + 1 + (mtwist_rand (&mt) & 8) * 0.05;
 
 		if (i & 1) {
 			p->type = pt_blob;
-			p->color = 66 + rand () % 6;
+			p->color = 66 + mtwist_rand (&mt) % 6;
 		} else {
 			p->type = pt_blob2;
-			p->color = 150 + rand () % 6;
+			p->color = 150 + mtwist_rand (&mt) % 6;
 		}
 		p->phys = R_ParticlePhysics (p->type);
 		for (j = 0; j < 3; j++) {
-			p->org[j] = org[j] + ((rand () % 32) - 16);
-			p->vel[j] = (rand () % 512) - 256;
+			p->org[j] = org[j] + ((mtwist_rand (&mt) % 32) - 16);
+			p->vel[j] = (mtwist_rand (&mt) % 512) - 256;
 		}
 	}
 }
@@ -238,13 +241,13 @@ R_RunParticleEffect_QF (const vec3_t org, const vec3_t dir, int color,
 		p->next = active_particles;
 		active_particles = p;
 
-		p->die = vr_data.realtime + 0.1 * (rand () % 5);
-		p->color = (color & ~7) + (rand () & 7);
+		p->die = vr_data.realtime + 0.1 * (mtwist_rand (&mt) % 5);
+		p->color = (color & ~7) + (mtwist_rand (&mt) & 7);
 		p->type = pt_grav;
 		p->phys = R_ParticlePhysics (p->type);
 		for (j = 0; j < 3; j++) {
-			p->org[j] = org[j] + ((rand () & 15) - 8);
-			p->vel[j] = dir[j];	// + (rand()%300)-150;
+			p->org[j] = org[j] + ((mtwist_rand (&mt) & 15) - 8);
+			p->vel[j] = dir[j];	// + (mtwist_rand (&mt)%300)-150;
 		}
 	}
 }
@@ -312,21 +315,21 @@ R_LavaSplash_QF (const vec3_t org)
 				p->next = active_particles;
 				active_particles = p;
 
-				p->die = vr_data.realtime + 2 + (rand () & 31) * 0.02;
-				p->color = 224 + (rand () & 7);
+				p->die = vr_data.realtime + 2 + (mtwist_rand (&mt) & 31) * 0.02;
+				p->color = 224 + (mtwist_rand (&mt) & 7);
 				p->type = pt_grav;
 				p->phys = R_ParticlePhysics (p->type);
 
-				dir[0] = j * 8 + (rand () & 7);
-				dir[1] = i * 8 + (rand () & 7);
+				dir[0] = j * 8 + (mtwist_rand (&mt) & 7);
+				dir[1] = i * 8 + (mtwist_rand (&mt) & 7);
 				dir[2] = 256;
 
 				p->org[0] = org[0] + dir[0];
 				p->org[1] = org[1] + dir[1];
-				p->org[2] = org[2] + (rand () & 63);
+				p->org[2] = org[2] + (mtwist_rand (&mt) & 63);
 
 				VectorNormalize (dir);
-				vel = 50 + (rand () & 63);
+				vel = 50 + (mtwist_rand (&mt) & 63);
 				VectorScale (dir, vel, p->vel);
 			}
 }
@@ -352,8 +355,8 @@ R_TeleportSplash_QF (const vec3_t org)
 				p->next = active_particles;
 				active_particles = p;
 
-				p->die = vr_data.realtime + 0.2 + (rand () & 7) * 0.02;
-				p->color = 7 + (rand () & 7);
+				p->die = vr_data.realtime + 0.2 + (mtwist_rand (&mt) & 7) * 0.02;
+				p->color = 7 + (mtwist_rand (&mt) & 7);
 				p->type = pt_grav;
 				p->phys = R_ParticlePhysics (p->type);
 
@@ -361,12 +364,12 @@ R_TeleportSplash_QF (const vec3_t org)
 				dir[1] = i * 8;
 				dir[2] = k * 8;
 
-				p->org[0] = org[0] + i + (rand () & 3);
-				p->org[1] = org[1] + j + (rand () & 3);
-				p->org[2] = org[2] + k + (rand () & 3);
+				p->org[0] = org[0] + i + (mtwist_rand (&mt) & 3);
+				p->org[1] = org[1] + j + (mtwist_rand (&mt) & 3);
+				p->org[2] = org[2] + k + (mtwist_rand (&mt) & 3);
 
 				VectorNormalize (dir);
-				vel = 50 + (rand () & 63);
+				vel = 50 + (mtwist_rand (&mt) & 63);
 				VectorScale (dir, vel, p->vel);
 			}
 }
@@ -396,10 +399,10 @@ R_DarkFieldParticles_ID (const entity_t *ent)
                 p->next = active_particles;
 				active_particles = p;
 
-				rnd = rand ();
+				rnd = mtwist_rand (&mt);
 
 				p->die = vr_data.realtime + 0.2 + (rnd & 7) * 0.02;
-				p->color = 150 + rand () % 6;
+				p->color = 150 + mtwist_rand (&mt) % 6;
 				p->type = pt_slowgrav;
 				p->phys = R_ParticlePhysics (p->type);
 				dir[0] = j * 8;
@@ -434,7 +437,7 @@ R_EntityParticles_ID (const entity_t *ent)
 
 	if (!avelocities[0][0]) {
 		for (i = 0; i < NUMVERTEXNORMALS * 3; i++)
-			avelocities[0][i] = (rand () & 255) * 0.01;
+			avelocities[0][i] = (mtwist_rand (&mt) & 255) * 0.01;
 	}
 
 	for (i = 0; i < NUMVERTEXNORMALS; i++) {
@@ -502,12 +505,12 @@ R_RocketTrail_QF (const entity_t *ent)
 		VectorZero (p->vel);
 
 		p->die = vr_data.realtime + 2;
-		p->ramp = (rand () & 3);
+		p->ramp = (mtwist_rand (&mt) & 3);
 		p->color = ramp3[(int) p->ramp];
 		p->type = pt_fire;
 		p->phys = R_ParticlePhysics (p->type);
 		for (j = 0; j < 3; j++)
-			p->org[j] = old_origin[j] + ((rand () % 6) - 3);
+			p->org[j] = old_origin[j] + ((mtwist_rand (&mt) % 6) - 3);
 
 		VectorAdd (old_origin, vec, old_origin);
 	}
@@ -541,12 +544,12 @@ R_GrenadeTrail_QF (const entity_t *ent)
 		VectorZero (p->vel);
 
 		p->die = vr_data.realtime + 2;
-		p->ramp = (rand () & 3) + 2;
+		p->ramp = (mtwist_rand (&mt) & 3) + 2;
 		p->color = ramp3[(int) p->ramp];
 		p->type = pt_fire;
 		p->phys = R_ParticlePhysics (p->type);
 		for (j = 0; j < 3; j++)
-			p->org[j] = old_origin[j] + ((rand () % 6) - 3);
+			p->org[j] = old_origin[j] + ((mtwist_rand (&mt) % 6) - 3);
 
 		VectorAdd (old_origin, vec, old_origin);
 	}
@@ -582,9 +585,9 @@ R_BloodTrail_QF (const entity_t *ent)
 		p->die = vr_data.realtime + 2;
 		p->type = pt_slowgrav;
 		p->phys = R_ParticlePhysics (p->type);
-		p->color = 67 + (rand () & 3);
+		p->color = 67 + (mtwist_rand (&mt) & 3);
 		for (j = 0; j < 3; j++)
-			p->org[j] = old_origin[j] + ((rand () % 6) - 3);
+			p->org[j] = old_origin[j] + ((mtwist_rand (&mt) % 6) - 3);
 		break;
 
 		VectorAdd (old_origin, vec, old_origin);
@@ -621,9 +624,9 @@ R_SlightBloodTrail_QF (const entity_t *ent)
 		p->die = vr_data.realtime + 2;
 		p->type = pt_slowgrav;
 		p->phys = R_ParticlePhysics (p->type);
-		p->color = 67 + (rand () & 3);
+		p->color = 67 + (mtwist_rand (&mt) & 3);
 		for (j = 0; j < 3; j++)
-			p->org[j] = old_origin[j] + ((rand () % 6) - 3);
+			p->org[j] = old_origin[j] + ((mtwist_rand (&mt) % 6) - 3);
 
 		VectorAdd (old_origin, vec, old_origin);
 	}
@@ -753,9 +756,9 @@ R_VoorTrail_QF (const entity_t *ent)
 		p->die = vr_data.realtime + 0.3;
 		p->type = pt_static;
 		p->phys = R_ParticlePhysics (p->type);
-		p->color = 9 * 16 + 8 + (rand () & 3);
+		p->color = 9 * 16 + 8 + (mtwist_rand (&mt) & 3);
 		for (j = 0; j < 3; j++)
-			p->org[j] = old_origin[j] + ((rand () & 15) - 8);
+			p->org[j] = old_origin[j] + ((mtwist_rand (&mt) & 15) - 8);
 
 		VectorAdd (old_origin, vec, old_origin);
 	}
@@ -905,14 +908,14 @@ R_Particle_NewRandom (ptype_t type, int texnum, const vec3_t org, int org_fuzz,
 	int         rnd;
 	vec3_t      porg, pvel;
 
-	rnd = rand ();
+	rnd = mtwist_rand (&mt);
 	porg[0] = o_fuzz * ((rnd & 63) - 31.5) / 63.0 + org[0];
-	porg[1] = o_fuzz * (((rnd >> 5) & 63) - 31.5) / 63.0 + org[1];
-	porg[2] = o_fuzz * (((rnd >> 9) & 63) - 31.5) / 63.0 + org[2];
-	rnd = rand ();
+	porg[1] = o_fuzz * (((rnd >> 6) & 63) - 31.5) / 63.0 + org[1];
+	porg[2] = o_fuzz * (((rnd >> 10) & 63) - 31.5) / 63.0 + org[2];
+	rnd = mtwist_rand (&mt);
 	pvel[0] = v_fuzz * ((rnd & 63) - 31.5) / 63.0;
-	pvel[1] = v_fuzz * (((rnd >> 5) & 63) - 31.5) / 63.0;
-	pvel[2] = v_fuzz * (((rnd >> 9) & 63) - 31.5) / 63.0;
+	pvel[1] = v_fuzz * (((rnd >> 6) & 63) - 31.5) / 63.0;
+	pvel[2] = v_fuzz * (((rnd >> 10) & 63) - 31.5) / 63.0;
 
 	R_Particle_New (type, texnum, porg, scale, pvel, die, color, alpha, ramp);
 }
diff --git a/libs/video/renderer/sw32/sw32_rpart.c b/libs/video/renderer/sw32/sw32_rpart.c
index 4f2829fb2..3ae503213 100644
--- a/libs/video/renderer/sw32/sw32_rpart.c
+++ b/libs/video/renderer/sw32/sw32_rpart.c
@@ -40,6 +40,7 @@
 #endif
 
 #include "QF/cvar.h"
+#include "QF/mersenne.h"
 #include "QF/qargs.h"
 #include "QF/quakefs.h"
 #include "QF/render.h"
@@ -53,10 +54,13 @@ static int		ramp1[8] = { 0x6f, 0x6d, 0x6b, 0x69, 0x67, 0x65, 0x63, 0x61 };
 //static int	ramp2[8] = { 0x6f, 0x6e, 0x6d, 0x6c, 0x6b, 0x6a, 0x68, 0x66 };
 static int		ramp3[8] = { 0x6d, 0x6b, 6, 5, 4, 3 };
 
+static mtstate_t mt;	// private PRNG state
+
 
 void
 sw32_R_InitParticles (void)
 {
+	mtwist_seed (&mt, 0xdeadbeef);
 }
 
 void
@@ -149,18 +153,18 @@ R_ParticleExplosion_QF (const vec3_t org)
 
 		p->die = vr_data.realtime + 5;
 		p->color = ramp1[0];
-		p->ramp = rand () & 3;
+		p->ramp = mtwist_rand (&mt) & 3;
 		if (i & 1) {
 			p->type = pt_explode;
 			for (j = 0; j < 3; j++) {
-				p->org[j] = org[j] + ((rand () % 32) - 16);
-				p->vel[j] = (rand () % 512) - 256;
+				p->org[j] = org[j] + ((mtwist_rand (&mt) % 32) - 16);
+				p->vel[j] = (mtwist_rand (&mt) % 512) - 256;
 			}
 		} else {
 			p->type = pt_explode2;
 			for (j = 0; j < 3; j++) {
-				p->org[j] = org[j] + ((rand () % 32) - 16);
-				p->vel[j] = (rand () % 512) - 256;
+				p->org[j] = org[j] + ((mtwist_rand (&mt) % 32) - 16);
+				p->vel[j] = (mtwist_rand (&mt) % 512) - 256;
 			}
 		}
 		p->phys = R_ParticlePhysics (p->type);
@@ -191,8 +195,8 @@ R_ParticleExplosion2_QF (const vec3_t org, int colorStart, int colorLength)
 		p->phys = R_ParticlePhysics (p->type);
 		for (j=0 ; j<3 ; j++)
 		{
-			p->org[j] = org[j] + ((rand()%32)-16);
-			p->vel[j] = (rand()%512)-256;
+			p->org[j] = org[j] + ((mtwist_rand (&mt)%32)-16);
+			p->vel[j] = (mtwist_rand (&mt)%512)-256;
 		}
 	}
 }
@@ -214,21 +218,21 @@ R_BlobExplosion_QF (const vec3_t org)
 		p->next = active_particles;
 		active_particles = p;
 
-		p->die = vr_data.realtime + 1 + (rand () & 8) * 0.05;
+		p->die = vr_data.realtime + 1 + (mtwist_rand (&mt) & 8) * 0.05;
 
 		if (i & 1) {
 			p->type = pt_blob;
-			p->color = 66 + rand () % 6;
+			p->color = 66 + mtwist_rand (&mt) % 6;
 			for (j = 0; j < 3; j++) {
-				p->org[j] = org[j] + ((rand () % 32) - 16);
-				p->vel[j] = (rand () % 512) - 256;
+				p->org[j] = org[j] + ((mtwist_rand (&mt) % 32) - 16);
+				p->vel[j] = (mtwist_rand (&mt) % 512) - 256;
 			}
 		} else {
 			p->type = pt_blob2;
-			p->color = 150 + rand () % 6;
+			p->color = 150 + mtwist_rand (&mt) % 6;
 			for (j = 0; j < 3; j++) {
-				p->org[j] = org[j] + ((rand () % 32) - 16);
-				p->vel[j] = (rand () % 512) - 256;
+				p->org[j] = org[j] + ((mtwist_rand (&mt) % 32) - 16);
+				p->vel[j] = (mtwist_rand (&mt) % 512) - 256;
 			}
 		}
 		p->phys = R_ParticlePhysics (p->type);
@@ -256,21 +260,21 @@ R_LavaSplash_QF (const vec3_t org)
 				p->next = active_particles;
 				active_particles = p;
 
-				p->die = vr_data.realtime + 2 + (rand () & 31) * 0.02;
-				p->color = 224 + (rand () & 7);
+				p->die = vr_data.realtime + 2 + (mtwist_rand (&mt) & 31) * 0.02;
+				p->color = 224 + (mtwist_rand (&mt) & 7);
 				p->type = pt_grav;
 				p->phys = R_ParticlePhysics (p->type);
 
-				dir[0] = j * 8 + (rand () & 7);
-				dir[1] = i * 8 + (rand () & 7);
+				dir[0] = j * 8 + (mtwist_rand (&mt) & 7);
+				dir[1] = i * 8 + (mtwist_rand (&mt) & 7);
 				dir[2] = 256;
 
 				p->org[0] = org[0] + dir[0];
 				p->org[1] = org[1] + dir[1];
-				p->org[2] = org[2] + (rand () & 63);
+				p->org[2] = org[2] + (mtwist_rand (&mt) & 63);
 
 				VectorNormalize (dir);
-				vel = 50 + (rand () & 63);
+				vel = 50 + (mtwist_rand (&mt) & 63);
 				VectorScale (dir, vel, p->vel);
 			}
 }
@@ -296,8 +300,8 @@ R_TeleportSplash_QF (const vec3_t org)
 				p->next = active_particles;
 				active_particles = p;
 
-				p->die = vr_data.realtime + 0.2 + (rand () & 7) * 0.02;
-				p->color = 7 + (rand () & 7);
+				p->die = vr_data.realtime + 0.2 + (mtwist_rand (&mt) & 7) * 0.02;
+				p->color = 7 + (mtwist_rand (&mt) & 7);
 				p->type = pt_grav;
 				p->phys = R_ParticlePhysics (p->type);
 
@@ -305,12 +309,12 @@ R_TeleportSplash_QF (const vec3_t org)
 				dir[1] = i * 8;
 				dir[2] = k * 8;
 
-				p->org[0] = org[0] + i + (rand () & 3);
-				p->org[1] = org[1] + j + (rand () & 3);
-				p->org[2] = org[2] + k + (rand () & 3);
+				p->org[0] = org[0] + i + (mtwist_rand (&mt) & 3);
+				p->org[1] = org[1] + j + (mtwist_rand (&mt) & 3);
+				p->org[2] = org[2] + k + (mtwist_rand (&mt) & 3);
 
 				VectorNormalize (dir);
-				vel = 50 + (rand () & 63);
+				vel = 50 + (mtwist_rand (&mt) & 63);
 				VectorScale (dir, vel, p->vel);
 			}
 		}
@@ -339,10 +343,10 @@ R_DarkFieldParticles_ID (const entity_t *ent)
 				p->next = active_particles;
 				active_particles = p;
 
-				rnd = rand ();
+				rnd = mtwist_rand (&mt);
 
 				p->die = vr_data.realtime + 0.2 + (rnd & 7) * 0.02;
-				p->color = 150 + rand () % 6;
+				p->color = 150 + mtwist_rand (&mt) % 6;
 				p->type = pt_slowgrav;
 				p->phys = R_ParticlePhysics (p->type);
 
@@ -375,7 +379,7 @@ R_EntityParticles_ID (const entity_t *ent)
 
 	if (!avelocities[0][0]) {
 		for (i = 0; i < NUMVERTEXNORMALS * 3; i++)
-			avelocities[0][i] = (rand () & 255) * 0.01;
+			avelocities[0][i] = (mtwist_rand (&mt) & 255) * 0.01;
 	}
 
 	for (i = 0; i < NUMVERTEXNORMALS; i++) {
@@ -433,13 +437,13 @@ R_RunParticleEffect_QF (const vec3_t org, const vec3_t dir, int color,
 		p->next = active_particles;
 		active_particles = p;
 
-		p->die = vr_data.realtime + 0.1 * (rand () % 5);
-		p->color = (color & ~7) + (rand () & 7);
+		p->die = vr_data.realtime + 0.1 * (mtwist_rand (&mt) % 5);
+		p->color = (color & ~7) + (mtwist_rand (&mt) & 7);
 		p->type = pt_slowgrav;
 		p->phys = R_ParticlePhysics (p->type);
 		for (j = 0; j < 3; j++) {
-			p->org[j] = org[j] + ((rand () & 15) - 8);
-			p->vel[j] = dir[j];	// + (rand()%300)-150;
+			p->org[j] = org[j] + ((mtwist_rand (&mt) & 15) - 8);
+			p->vel[j] = dir[j];	// + (mtwist_rand (&mt)%300)-150;
 		}
 	}
 }
@@ -514,12 +518,12 @@ R_RocketTrail_QF (const entity_t *ent)
 		VectorZero (p->vel);
 
 		p->die = vr_data.realtime + 2;
-		p->ramp = (rand () & 3);
+		p->ramp = (mtwist_rand (&mt) & 3);
 		p->color = ramp3[(int) p->ramp];
 		p->type = pt_fire;
 		p->phys = R_ParticlePhysics (p->type);
 		for (j = 0; j < 3; j++)
-			p->org[j] = old_origin[j] + ((rand () % 6) - 3);
+			p->org[j] = old_origin[j] + ((mtwist_rand (&mt) % 6) - 3);
 
 		VectorAdd (old_origin, vec, old_origin);
 	}
@@ -553,12 +557,12 @@ R_GrenadeTrail_QF (const entity_t *ent)
 		VectorZero (p->vel);
 
 		p->die = vr_data.realtime + 2;
-		p->ramp = (rand () & 3) + 2;
+		p->ramp = (mtwist_rand (&mt) & 3) + 2;
 		p->color = ramp3[(int) p->ramp];
 		p->type = pt_fire;
 		p->phys = R_ParticlePhysics (p->type);
 		for (j = 0; j < 3; j++)
-			p->org[j] = old_origin[j] + ((rand () % 6) - 3);
+			p->org[j] = old_origin[j] + ((mtwist_rand (&mt) % 6) - 3);
 
 		VectorAdd (old_origin, vec, old_origin);
 	}
@@ -594,9 +598,9 @@ R_BloodTrail_QF (const entity_t *ent)
 		p->die = vr_data.realtime + 2;
 		p->type = pt_slowgrav;
 		p->phys = R_ParticlePhysics (p->type);
-		p->color = 67 + (rand () & 3);
+		p->color = 67 + (mtwist_rand (&mt) & 3);
 		for (j = 0; j < 3; j++)
-			p->org[j] = old_origin[j] + ((rand () % 6) - 3);
+			p->org[j] = old_origin[j] + ((mtwist_rand (&mt) % 6) - 3);
 		break;
 
 		VectorAdd (old_origin, vec, old_origin);
@@ -633,9 +637,9 @@ R_SlightBloodTrail_QF (const entity_t *ent)
 		p->die = vr_data.realtime + 2;
 		p->type = pt_slowgrav;
 		p->phys = R_ParticlePhysics (p->type);
-		p->color = 67 + (rand () & 3);
+		p->color = 67 + (mtwist_rand (&mt) & 3);
 		for (j = 0; j < 3; j++)
-			p->org[j] = old_origin[j] + ((rand () % 6) - 3);
+			p->org[j] = old_origin[j] + ((mtwist_rand (&mt) % 6) - 3);
 
 		VectorAdd (old_origin, vec, old_origin);
 	}
@@ -765,9 +769,9 @@ R_VoorTrail_QF (const entity_t *ent)
 		p->die = vr_data.realtime + 0.3;
 		p->type = pt_static;
 		p->phys = R_ParticlePhysics (p->type);
-		p->color = 9 * 16 + 8 + (rand () & 3);
+		p->color = 9 * 16 + 8 + (mtwist_rand (&mt) & 3);
 		for (j = 0; j < 3; j++)
-			p->org[j] = old_origin[j] + ((rand () & 15) - 8);
+			p->org[j] = old_origin[j] + ((mtwist_rand (&mt) & 15) - 8);
 
 		VectorAdd (old_origin, vec, old_origin);
 	}
@@ -918,14 +922,14 @@ sw32_R_Particle_NewRandom (ptype_t type, int texnum, const vec3_t org,
 	int         rnd;
 	vec3_t      porg, pvel;
 
-	rnd = rand ();
+	rnd = mtwist_rand (&mt);
 	porg[0] = o_fuzz * ((rnd & 63) - 31.5) / 63.0 + org[0];
-	porg[1] = o_fuzz * (((rnd >> 5) & 63) - 31.5) / 63.0 + org[1];
-	porg[2] = o_fuzz * (((rnd >> 9) & 63) - 31.5) / 63.0 + org[2];
-	rnd = rand ();
+	porg[1] = o_fuzz * (((rnd >> 6) & 63) - 31.5) / 63.0 + org[1];
+	porg[2] = o_fuzz * (((rnd >> 12) & 63) - 31.5) / 63.0 + org[2];
+	rnd = mtwist_rand (&mt);
 	pvel[0] = v_fuzz * ((rnd & 63) - 31.5) / 63.0;
-	pvel[1] = v_fuzz * (((rnd >> 5) & 63) - 31.5) / 63.0;
-	pvel[2] = v_fuzz * (((rnd >> 9) & 63) - 31.5) / 63.0;
+	pvel[1] = v_fuzz * (((rnd >> 6) & 63) - 31.5) / 63.0;
+	pvel[2] = v_fuzz * (((rnd >> 12) & 63) - 31.5) / 63.0;
 
 	sw32_R_Particle_New (type, texnum, porg, scale, pvel, die, color, alpha, ramp);
 }