Clean up water skip conditions

- Use Digital Empire's water running conditions (fully prevents ever being able to water-run on water that isn't level)
- Code cleanup of other parts of this code
- Made the threshold for water skipping much more strict
- Fixed water skip being scaled to player scale instead of map scale
- Make water run / tripwire easier for rubberbanding bots

src/k_kart.c

@@ -3232,7 +3232,7 @@ tripwirepass_t K_TripwirePassConditions(player_t *player)
 
 	if (
 			player->flamedash ||
-			player->speed > 2 * K_GetKartSpeed(player, false, true)
+			player->speed > 2 * K_GetKartSpeed(player, false, false)
 	)
 		return TRIPWIRE_BOOST;
 
@@ -3250,6 +3250,11 @@ boolean K_TripwirePass(player_t *player)
 	return (player->tripwirePass != TRIPWIRE_NONE);
 }
 
+boolean K_MovingHorizontally(mobj_t *mobj)
+{
+	return (P_AproxDistance(mobj->momx, mobj->momy) / 5 > abs(mobj->momz));
+}
+
 boolean K_WaterRun(player_t *player)
 {
 	if (
@@ -3257,12 +3262,30 @@ boolean K_WaterRun(player_t *player)
 			player->sneakertimer ||
 			player->tiregrease ||
 			player->flamedash ||
-			player->speed > 2 * K_GetKartSpeed(player, false, true)
+			player->speed > 2 * K_GetKartSpeed(player, false, false)
 	)
 		return true;
 	return false;
 }
 
+boolean K_WaterSkip(player_t *player)
+{
+	if (player->waterskip >= 2)
+	{
+		// Already finished waterskipping.
+		return false;
+	}
+
+	if (player->waterskip > 0)
+	{
+		// Already waterskipping.
+		// Simply make sure you haven't slowed down drastically.
+		return (player->speed > 20 * mapobjectscale);
+	}
+
+	return K_MovingHorizontally(player->mo);
+}
+
 static fixed_t K_FlameShieldDashVar(INT32 val)
 {
 	// 1 second = 75% + 50% top speed

src/k_kart.h

@@ -142,7 +142,9 @@ boolean K_ApplyOffroad(player_t *player);
 boolean K_SlopeResistance(player_t *player);
 tripwirepass_t K_TripwirePassConditions(player_t *player);
 boolean K_TripwirePass(player_t *player);
+boolean K_MovingHorizontally(mobj_t *mobj);
 boolean K_WaterRun(player_t *player);
+boolean K_WaterSkip(player_t *player);
 void K_ApplyTripWire(player_t *player, tripwirestate_t state);
 INT16 K_GetSpindashChargeTime(player_t *player);
 fixed_t K_GetSpindashChargeSpeed(player_t *player);

src/p_mobj.c

@@ -3073,25 +3073,92 @@ boolean P_SceneryZMovement(mobj_t *mo)
 	return true;
 }
 
+//
 // P_CanRunOnWater
 //
-// Returns true if player can waterrun on the 3D floor
+// Returns true if player can water run on a 3D floor
 //
 boolean P_CanRunOnWater(player_t *player, ffloor_t *rover)
 {
-	boolean flip = player->mo->eflags & MFE_VERTICALFLIP;
-	fixed_t surfaceheight = flip ? player->mo->waterbottom : player->mo->watertop;
-	fixed_t playerbottom = flip ? (player->mo->z + player->mo->height) : player->mo->z;
-	fixed_t clip = flip ? (surfaceheight - playerbottom) : (playerbottom - surfaceheight);
-	fixed_t span = player->mo->watertop - player->mo->waterbottom;
+	const boolean flip = (player->mo->eflags & MFE_VERTICALFLIP);
+	fixed_t surfaceheight = INT32_MAX;
+	fixed_t playerbottom = INT32_MAX;
+	fixed_t surfDiff = INT32_MAX;
+	fixed_t maxStep = INT32_MAX;
+	boolean doifit = false;
 
-	return
-		clip > -(player->mo->height / 2) &&
-		span > player->mo->height &&
-		player->speed / 5 > abs(player->mo->momz) &&
-		player->speed > K_GetKartSpeed(player, false, false) &&
-		K_WaterRun(player) &&
-		(rover->flags & FF_SWIMMABLE);
+	pslope_t *waterSlope = NULL;
+	angle_t ourZAng = 0;
+	angle_t waterZAng = 0;
+
+	if (rover == NULL)
+	{
+		// No rover.
+		return false;
+	}
+
+	if (!(rover->flags & FF_SWIMMABLE))
+	{
+		// It's not even a water FOF.
+		return false;
+	}
+
+	if (player->carry != CR_NONE) // Special carry state.
+	{
+		// No good player state.
+		return false;
+	}
+
+	if (P_IsObjectOnGround(player->mo) == false)
+	{
+		// Don't allow jumping onto water to start a water run.
+		// (Already water running still counts as being on the ground.)
+		return false;
+	}
+
+	if (K_WaterRun(player) == false)
+	{
+		// Basic conditions for enabling water run.
+		return false;
+	}
+
+	if (player->mo->standingslope != NULL)
+	{
+		ourZAng = player->mo->standingslope->zangle;
+	}
+ 
+	waterSlope = (flip ? *rover->b_slope : *rover->t_slope);
+	if (waterSlope != NULL)
+	{
+		waterZAng = waterSlope->zangle;
+	}
+ 
+	if (ourZAng != waterZAng)
+	{
+		// The surface slopes are different.
+		return false;
+	}
+ 
+	surfaceheight = flip ? P_GetFFloorBottomZAt(rover, player->mo->x, player->mo->y) : P_GetFFloorTopZAt(rover, player->mo->x, player->mo->y);
+	playerbottom = flip ? (player->mo->z + player->mo->height) : player->mo->z;
+ 
+	doifit = flip ? (surfaceheight - player->mo->floorz >= player->mo->height) : (player->mo->ceilingz - surfaceheight >= player->mo->height);
+ 
+	if (!doifit)
+	{
+		// Player can't fit in this space.
+		return false;
+	}
+ 
+	surfDiff = flip ? (surfaceheight - playerbottom) : (playerbottom - surfaceheight);
+	maxStep = P_GetThingStepUp(player->mo);
+	if (surfDiff <= maxStep && surfDiff >= 0)
+	{
+		// We start water run IF we can step-down!
+		return true;
+	}
+ 
+	return false;
 }
 
 boolean P_CheckSolidFFloorSurface(player_t *player, ffloor_t *rover)
@@ -3308,23 +3375,19 @@ void P_MobjCheckWater(mobj_t *mobj)
 
 				splish->destscale = mobj->scale;
 				P_SetScale(splish, mobj->scale);
+
+				// skipping stone!
+				if (K_WaterSkip(p) == true)
+				{
+					const fixed_t hop = 5 * mapobjectscale;
+
+					mobj->momx = (4*mobj->momx)/5;
+					mobj->momy = (4*mobj->momy)/5;
+					mobj->momz = hop * P_MobjFlip(mobj);
+
+					p->waterskip++;
+				}
 			}
-
-			// skipping stone!
-			if (p && p->waterskip < 2
-				&& ((p->speed/3 > abs(mobj->momz)) // Going more forward than horizontal, so you can skip across the water.
-				|| (p->speed > 20*mapobjectscale && p->waterskip)) // Already skipped once, so you can skip once more!
-				&& (splashValid == true))
-			{
-				const fixed_t hop = 5 * mobj->scale;
-
-				mobj->momx = (4*mobj->momx)/5;
-				mobj->momy = (4*mobj->momy)/5;
-				mobj->momz = hop * P_MobjFlip(mobj);
-
-				p->waterskip++;
-			}
-
 		}
 		else if (P_MobjFlip(mobj) * mobj->momz > 0)
 		{