From 5ece4825c0949ce6c12373ffec01f17a3951cfb4 Mon Sep 17 00:00:00 2001
From: Sally Coolatta <tehrealsalt@gmail.com>
Date: Sat, 2 Apr 2022 02:25:25 -0400
Subject: [PATCH] Smooth landing support for bots

---
 src/k_bot.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/src/k_bot.c b/src/k_bot.c
index b3f73b8ac..5d512f54c 100644
--- a/src/k_bot.c
+++ b/src/k_bot.c
@@ -1062,6 +1062,55 @@ static void K_BotTrick(player_t *player, ticcmd_t *cmd, line_t *botController)
 	}
 }
 
+/*--------------------------------------------------
+	static angle_t K_BotSmoothLanding(player_t *player, angle_t destangle)
+
+		Calculates a new destination angle while in the air,
+		to be able to successfully smooth land.
+
+	Input Arguments:-
+		player - Bot player to check.
+		destangle - Previous destination angle.
+
+	Return:-
+		New destination angle.
+--------------------------------------------------*/
+static angle_t K_BotSmoothLanding(player_t *player, angle_t destangle)
+{
+	angle_t newAngle = destangle;
+	boolean air = !P_IsObjectOnGround(player->mo);
+	angle_t steepVal = air ? STUMBLE_STEEP_VAL_AIR : STUMBLE_STEEP_VAL;
+	angle_t slopeSteep = max(AngleDelta(player->mo->pitch, 0), AngleDelta(player->mo->roll, 0));
+
+	if (slopeSteep > steepVal)
+	{
+		fixed_t pitchMul = -FINESINE(destangle >> ANGLETOFINESHIFT);
+		fixed_t rollMul = FINECOSINE(destangle >> ANGLETOFINESHIFT);
+		angle_t testAngles[2];
+		angle_t testDeltas[2];
+		UINT8 i;
+
+		testAngles[0] = R_PointToAngle2(0, 0, rollMul, pitchMul);
+		testAngles[1] = R_PointToAngle2(0, 0, -rollMul, -pitchMul);
+
+		for (i = 0; i < 2; i++)
+		{
+			testDeltas[i] = AngleDelta(testAngles[i], destangle);
+		}
+
+		if (testDeltas[1] < testDeltas[0])
+		{
+			return testAngles[1];
+		}
+		else
+		{
+			return testAngles[0];
+		}
+	}
+
+	return newAngle;
+}
+
 /*--------------------------------------------------
 	static INT32 K_HandleBotTrack(player_t *player, ticcmd_t *cmd, botprediction_t *predict)
 
@@ -1085,6 +1134,8 @@ static INT32 K_HandleBotTrack(player_t *player, ticcmd_t *cmd, botprediction_t *
 
 	I_Assert(predict != NULL);
 
+	destangle = K_BotSmoothLanding(player, destangle);
+
 	moveangle = player->mo->angle;
 	angle = (moveangle - destangle);
 
@@ -1227,6 +1278,8 @@ static INT32 K_HandleBotReverse(player_t *player, ticcmd_t *cmd, botprediction_t
 		}
 	}
 
+	destangle = K_BotSmoothLanding(player, destangle);
+
 	// Calculate turn direction first.
 	moveangle = player->mo->angle;
 	angle = (moveangle - destangle);