Add per-actor friction

- This is multiplied by the sector's friction.
- This is intentionally not serialized yet, while awaiting feedback.

src/actor.h

@@ -906,6 +906,7 @@ public:
 	fixed_t			wallbouncefactor;	// The bounce factor for walls can be different.
 	int				bouncecount;	// Strife's grenades only bounce twice before exploding
 	fixed_t			gravity;		// [GRB] Gravity factor
+	fixed_t			Friction;
 	int 			FastChaseStrafeCount;
 	fixed_t			pushfactor;
 	int				lastpush;

src/p_acs.cpp

@@ -3605,7 +3605,8 @@ enum
 	APROP_MeleeRange	= 38,
 	APROP_ViewHeight	= 39,
 	APROP_AttackZOffset	= 40,
-	APROP_StencilColor	= 41
+	APROP_StencilColor	= 41,
+	APROP_Friction		= 42,
 };
 
 // These are needed for ACS's APROP_RenderStyle
@@ -3839,6 +3840,9 @@ void DLevelScript::DoSetActorProperty (AActor *actor, int property, int value)
 		actor->SetShade(value);
 		break;
 
+	case APROP_Friction:
+		actor->Friction = value;
+
 	default:
 		// do nothing.
 		break;
@@ -3937,6 +3941,7 @@ int DLevelScript::GetActorProperty (int tid, int property, const SDWORD *stack,
 	case APROP_Species:		return GlobalACSStrings.AddString(actor->GetSpecies(), stack, stackdepth);
 	case APROP_NameTag:		return GlobalACSStrings.AddString(actor->GetTag(), stack, stackdepth);
 	case APROP_StencilColor:return actor->fillcolor;
+	case APROP_Friction:	return actor->Friction;
 
 	default:				return 0;
 	}

src/p_map.cpp

@@ -555,6 +555,12 @@ int P_GetFriction (const AActor *mo, int *frictionfactor)
 		}
 	}
  
+	if (mo->Friction != FRACUNIT)
+	{
+		friction = clamp(FixedMul(friction, mo->Friction), 0, FRACUNIT);
+		movefactor = FrictionToMoveFactor(friction);
+	}
+
 	if (frictionfactor)
 		*frictionfactor = movefactor;
 

src/p_spec.cpp

@@ -1990,26 +1990,12 @@ void P_SetSectorFriction (int tag, int amount, bool alterFlag)
 	friction = (0x1EB8*amount)/0x80 + 0xD001;
 
 	// killough 8/28/98: prevent odd situations
-	if (friction > FRACUNIT)
-		friction = FRACUNIT;
-	if (friction < 0)
-		friction = 0;
+	friction = clamp(friction, 0, FRACUNIT);
 
 	// The following check might seem odd. At the time of movement,
 	// the move distance is multiplied by 'friction/0x10000', so a
 	// higher friction value actually means 'less friction'.
-
-	// [RH] Twiddled these values so that velocity on ice (with
-	//		friction 0xf900) is the same as in Heretic/Hexen.
-	if (friction >= ORIG_FRICTION)	// ice
-//		movefactor = ((0x10092 - friction)*(0x70))/0x158;
-		movefactor = ((0x10092 - friction) * 1024) / 4352 + 568;
-	else
-		movefactor = ((friction - 0xDB34)*(0xA))/0x80;
-
-	// killough 8/28/98: prevent odd situations
-	if (movefactor < 32)
-		movefactor = 32;
+	movefactor = FrictionToMoveFactor(friction);
 
 	for (s = -1; (s = P_FindSectorFromTag (tag,s)) >= 0; )
 	{

src/p_spec.h

@@ -172,6 +172,25 @@ void	P_PlayerOnSpecialFlat (player_t *player, int floorType);
 void	P_SectorDamage(int tag, int amount, FName type, const PClass *protectClass, int flags);
 void	P_SetSectorFriction (int tag, int amount, bool alterFlag);
 
+inline fixed_t FrictionToMoveFactor(fixed_t friction)
+{
+	fixed_t movefactor;
+
+	// [RH] Twiddled these values so that velocity on ice (with
+	//		friction 0xf900) is the same as in Heretic/Hexen.
+	if (friction >= ORIG_FRICTION)	// ice
+//		movefactor = ((0x10092 - friction)*(0x70))/0x158;
+		movefactor = ((0x10092 - friction) * 1024) / 4352 + 568;
+	else
+		movefactor = ((friction - 0xDB34)*(0xA))/0x80;
+
+	// killough 8/28/98: prevent odd situations
+	if (movefactor < 32)
+		movefactor = 32;
+
+	return movefactor;
+}
+
 void P_GiveSecret(AActor *actor, bool printmessage, bool playsound, int sectornum);
 
 //

src/thingdef/thingdef_properties.cpp

@@ -1297,6 +1297,17 @@ DEFINE_PROPERTY(gravity, F, Actor)
 	defaults->gravity = i;
 }
 
+//==========================================================================
+//
+//==========================================================================
+DEFINE_PROPERTY(friction, F, Actor)
+{
+	PROP_FIXED_PARM(i, 0);
+
+	if (i < 0) I_Error ("Friction must not be negative.");
+	defaults->Friction = i;
+}
+
 //==========================================================================
 //
 //==========================================================================

wadsrc/static/actors/actor.txt

@@ -18,6 +18,7 @@ ACTOR Actor native //: Thinker
 	FloatSpeed 4
 	FloatBobPhase -1	// randomly initialize by default
 	Gravity 1
+	Friction 1
 	DamageFactor 1.0
 	PushFactor 0.25
 	WeaveIndexXY 0