From bac61bf05af9395e615e0caa9e26fdbec890a3cd Mon Sep 17 00:00:00 2001
From: Miloslav Ciz <drummyfish@disroot.org>
Date: Tue, 3 Dec 2024 22:59:07 +0100
Subject: [PATCH] Add air brake

---
 game.h   |  2 +-
 racing.h | 66 +++++++++++++++++++++++++++++++++++++++++---------------
 2 files changed, 50 insertions(+), 18 deletions(-)

diff --git a/game.h b/game.h
index 4fd8157..fd65413 100644
--- a/game.h
+++ b/game.h
@@ -237,7 +237,7 @@ uint8_t LCR_gameStep(uint32_t time)
 
 if ((LCR_racing.tick % 32) == 0)
 {
-  printf("speed: %d\n",LCR_racingGetCarSpeed());
+  printf("speed: %d\n",LCR_racingGetCarSpeedSigned());
 
 }
 
diff --git a/racing.h b/racing.h
index f5c2689..15d9a54 100644
--- a/racing.h
+++ b/racing.h
@@ -34,7 +34,7 @@ typedef int32_t LCR_GameUnit;  ///< abstract game unit
 //#define LCR_CAR_AIR_FRICTION ((LCR_GAME_UNIT * 3) / 4) 
 #define LCR_CAR_AIR_FRICTION 32
 
-#define LCR_CAR_STAND_FRICTION_MULTIPLIER 16
+#define LCR_CAR_STAND_FRICTION_MULTIPLIER 32
 #define LCR_CAR_STEER_FRICTION (TPE_F)
 #define LCR_CAR_ELASTICITY (TPE_F / 150)
 //#define LCR_CAR_ACCELERATION (LCR_PHYSICS_UNIT / 90)
@@ -79,7 +79,8 @@ uint8_t carNotOKCount;
   LCR_GameUnit wheelSteer;
 
 
-  LCR_GameUnit carSpeed;
+
+  LCR_GameUnit carSpeed; ///* Signed speed (negative if backwards)
 
 } LCR_racing;
 
@@ -382,11 +383,21 @@ TPE_Vec3 _LCR_racingEnvironmentFunction(TPE_Vec3 point, TPE_Unit maxDist)
   TPE_ENV_END
 }
 
-LCR_GameUnit LCR_racingGetCarSpeed(void)
+
+
+LCR_GameUnit LCR_racingGetCarSpeedUnsigned(void)
+{
+  return LCR_racing.carSpeed >= 0 ? LCR_racing.carSpeed :
+    (-1 * LCR_racing.carSpeed);
+}
+
+LCR_GameUnit LCR_racingGetCarSpeedSigned(void)
 {
   return LCR_racing.carSpeed;
 }
 
+
+
 uint8_t _LCR_racingCollisionHandler(uint16_t b1, uint16_t j1, uint16_t b2,
   uint16_t j2, TPE_Vec3 p)
 {
@@ -587,7 +598,7 @@ acc -=
 */
 
 acc = 
-  acc / (1 + (LCR_racing.carSpeed / LCR_CAR_AIR_FRICTION));
+  acc / (1 + (LCR_racingGetCarSpeedUnsigned() / LCR_CAR_AIR_FRICTION));
 
 /*
 if (acc < 0)
@@ -627,7 +638,7 @@ uint32_t LCR_racingStep(unsigned int input)
   LCR_LOG2("racing step start");
 
   uint32_t result = 0;
-  TPE_Vec3 carForw, carRight, carUp;
+  TPE_Vec3 carForw, carRight, carUp, carVel;
   uint8_t groundMat = LCR_BLOCK_MATERIAL_CONCRETE; // material under wheels
   int groundBlockIndex = -1;
 
@@ -645,6 +656,11 @@ uint32_t LCR_racingStep(unsigned int input)
 
   carUp = TPE_vec3Cross(carForw,carRight);
 
+  carVel = TPE_vec3(
+    LCR_racing.carBody.joints[4].velocity[0],
+    LCR_racing.carBody.joints[4].velocity[1],
+    LCR_racing.carBody.joints[4].velocity[2]);
+
   if ((LCR_racing.wheelCollisions & 0x0f) != 0x0f) // EXPERIMENTAL: don't apply gravity with all wheels on ground
     TPE_bodyApplyGravity(&(LCR_racing.carBody),LCR_GRAVITY);
 
@@ -686,17 +702,27 @@ uint32_t LCR_racingStep(unsigned int input)
         LCR_CAR_FORWARD_FRICTION_DIRT :
         LCR_CAR_FORWARD_FRICTION);
 
-
-// TODO: also apply (probably twice as much) when accelerating in opposite direction than vecolcity vec.
-if (!(input & (LCR_RACING_INPUT_FORW | LCR_RACING_INPUT_BACK)))
-  LCR_racing.carBody.friction *= LCR_CAR_STAND_FRICTION_MULTIPLIER;
-
-
-
+  if(!(input & (LCR_RACING_INPUT_FORW | LCR_RACING_INPUT_BACK)))
+    LCR_racing.carBody.friction *= LCR_CAR_STAND_FRICTION_MULTIPLIER;
+  else if (
+  ((input & LCR_RACING_INPUT_FORW) && (LCR_racing.carSpeed < 0)) ||
+  ((input & LCR_RACING_INPUT_BACK) && (LCR_racing.carSpeed > 0)))
+    LCR_racing.carBody.friction *= 2 * LCR_CAR_STAND_FRICTION_MULTIPLIER;
 
   if (input)
   {
     unsigned char steering = 0;
+  
+    if ((input & LCR_RACING_INPUT_BACK) &&
+      (LCR_racing.wheelCollisions & 0x0f) == 0x00) // in air?
+    {
+      LCR_LOG2("air brake");
+
+      for (int i = 0; i < LCR_CAR_JOINTS - 1; ++i)
+        for (int j = 0; j < 3; ++j)
+          LCR_racing.carBody.joints[i].velocity[j] =  
+            LCR_racing.carBody.joints[LCR_CAR_JOINTS - 1].velocity[j]; 
+    }
 
     // TODO: magic constants
 
@@ -704,7 +730,7 @@ if (!(input & (LCR_RACING_INPUT_FORW | LCR_RACING_INPUT_BACK)))
     {
       LCR_GameUnit rotateBy =
         (LCR_racing.wheelCollisions & 0x0f) ? // on ground slow down wheel rot.
-        (LCR_racingGetCarSpeed() / 16) : LCR_GAME_UNIT / 32;
+        (LCR_racingGetCarSpeedUnsigned() / 16) : LCR_GAME_UNIT / 32;
 
       if (!(input & LCR_RACING_INPUT_BACK))
         rotateBy *= -1;
@@ -801,12 +827,18 @@ if (!(input & (LCR_RACING_INPUT_FORW | LCR_RACING_INPUT_BACK)))
   TPE_worldStep(&(LCR_racing.physicsWorld));
   LCR_LOG2("stepping physics engine done");
 
-  LCR_racing.carSpeed = (TPE_vec3Len(TPE_vec3(
-    LCR_racing.carBody.joints[4].velocity[0],
-    LCR_racing.carBody.joints[4].velocity[1],
-    LCR_racing.carBody.joints[4].velocity[2])) * LCR_GAME_UNIT)
+
+
+  LCR_racing.carSpeed = (TPE_vec3Len(carVel) * LCR_GAME_UNIT)
     / LCR_PHYSICS_UNIT;
 
+
+if (TPE_vec3Dot(carVel,carForw) < 0)
+  LCR_racing.carSpeed *= -1;
+
+
+
+
   TPE_Vec3 tmpVec = LCR_racing.carPositions[0];
 
   TPE_Vec3 wheelAverage = _LCR_TPE_vec3DividePlain(