Limit COM_Rand to 24 bit

Novum · Jan 9, 2025 · a7f29bd · a7f29bd
1 parent 4067b2f
commit a7f29bd
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Showing 5 changed files with 12 additions and 10 deletions.
diff --git a/Quake/cl_parse.c b/Quake/cl_parse.c
@@ -528,7 +528,7 @@ static void CL_EntitiesDeltaed (void)
 				if (model->synctype == ST_FRAMETIME)
 					ent->syncbase = -cl.time;
 				else if (model->synctype == ST_RAND)
-					ent->syncbase = (float)(COM_Rand () & 0xffffff) / 0xffffff;
+					ent->syncbase = (float)COM_Rand () / COM_RAND_MAX;
 				else
 					ent->syncbase = 0.0;
 			}
@@ -1265,7 +1265,7 @@ static void CL_ParseUpdate (int bits)
 		if (model)
 		{
 			if (model->synctype == ST_RAND)
-				ent->syncbase = (float)(COM_Rand () & 0xffffff) / 0xffffff;
+				ent->syncbase = (float)COM_Rand () / COM_RAND_MAX;
 			else
 				ent->syncbase = 0.0;
 		}

diff --git a/Quake/common.c b/Quake/common.c
@@ -3205,5 +3205,5 @@ uint32_t COM_Rand ()
 	s1 ^= s0;
 	xorshiro_state[0] = rotl (s0, 26) ^ s1 ^ (s1 << 9);
 	xorshiro_state[1] = rotl (s1, 13);
-	return result;
+	return result & COM_RAND_MAX;
 }
diff --git a/Quake/common.h b/Quake/common.h
@@ -315,7 +315,9 @@ size_t		LOC_Format (const char *format, const char *(*getarg_fn) (int idx, void
 
 void	 COM_SeedRand (uint64_t seed);
 uint32_t COM_Rand (void);
-#define COM_RAND_MAX UINT32_MAX
+
+// Limit to 24 bits so values fit in float mantissa & don't get negative when casting to ints
+#define COM_RAND_MAX 0xFFFFFF
 
 //============================================================================
 

diff --git a/Quake/pr_ext.c b/Quake/pr_ext.c
@@ -3926,9 +3926,9 @@ static void PF_randomvector (void)
 	vec3_t temp;
 	do
 	{
-		temp[0] = (COM_Rand () & 0xffffff) * (2.0 / (float)0xffffff) - 1.0;
-		temp[1] = (COM_Rand () & 0xffffff) * (2.0 / (float)0xffffff) - 1.0;
-		temp[2] = (COM_Rand () & 0xffffff) * (2.0 / (float)0xffffff) - 1.0;
+		temp[0] = COM_Rand () * (2.0 / (float)COM_RAND_MAX) - 1.0;
+		temp[1] = COM_Rand () * (2.0 / (float)COM_RAND_MAX) - 1.0;
+		temp[2] = COM_Rand () * (2.0 / (float)COM_RAND_MAX) - 1.0;
 	} while (DotProduct (temp, temp) >= 1);
 	VectorCopy (temp, G_VECTOR (OFS_RETURN));
 }

diff --git a/Quake/r_part_fte.c b/Quake/r_part_fte.c
@@ -34,9 +34,9 @@ cvar_t r_fteparticles = {"r_fteparticles", "1", CVAR_ARCHIVE};
 #define USE_DECALS
 #define Con_Printf Con_SafePrintf
 
-#define frandom()  ((COM_Rand () & 0xFFFFFF) * (1.0f / (float)0xFFFFFF))
-#define crandom()  ((COM_Rand () & 0xFFFFFF) * (2.0f / (float)0xFFFFFF) - 1.0f)
-#define hrandom()  ((COM_Rand () & 0xFFFFFF) * (1.0f / (float)0xFFFFFF) - 0.5f)
+#define frandom()  (COM_Rand () * (1.0f / (float)COM_RAND_MAX))
+#define crandom()  (COM_Rand () * (2.0f / (float)COM_RAND_MAX) - 1.0f)
+#define hrandom()  (COM_Rand () * (1.0f / (float)COM_RAND_MAX) - 0.5f)
 #define particle_s fparticle_s
 #define particle_t fparticle_t
 typedef vec_t vec2_t[2];