implement fall damage

build_registries.js

@@ -416,6 +416,9 @@ ${Object.entries(itemsAndBlocks.items).map(c => `#define I_${c[0]} ${c[1]}`).joi
 // Biome identifiers
 ${biomes.map((c, i) => `#define W_${c} ${i}`).join("\n")}
 
+// Damage type identifiers
+${registries["damage_type"].map((c, i) => `#define D_${c} ${i}`).join("\n")}
+
 #endif
 `;
 

include/globals.h

@@ -65,6 +65,9 @@ typedef struct {
   #endif
   int8_t yaw;
   int8_t pitch;
+  short grounded_y;
+  uint8_t health;
+  uint8_t hunger;
   uint8_t hotbar;
   uint16_t inventory_items[41];
   uint16_t craft_items[9];

include/packets.h

@@ -7,9 +7,9 @@ int cs_clientInformation (int client_fd);
 int cs_pluginMessage (int client_fd);
 int cs_playerAction (int client_fd);
 int cs_useItemOn (int client_fd);
-int cs_setPlayerPositionAndRotation (int client_fd, double *x, double *y, double *z, float *yaw, float *pitch);
+int cs_setPlayerPositionAndRotation (int client_fd, double *x, double *y, double *z, float *yaw, float *pitch, uint8_t *on_ground);
-int cs_setPlayerPosition (int client_fd, double *x, double *y, double *z);
+int cs_setPlayerPosition (int client_fd, double *x, double *y, double *z, uint8_t *on_ground);
-int cs_setPlayerRotation(int client_fd, float *yaw, float *pitch);
+int cs_setPlayerRotation (int client_fd, float *yaw, float *pitch, uint8_t *on_ground);
 int cs_setHeldItem (int client_fd);
 int cs_clickContainer (int client_fd);
 int cs_closeContainer (int client_fd);
@@ -37,6 +37,8 @@ int sc_spawnEntityPlayer (int client_fd, PlayerData player);
 int sc_teleportEntity (int client_fd, int id, double x, double y, double z, float yaw, float pitch);
 int sc_setHeadRotation (int client_fd, int id, uint8_t yaw);
 int sc_updateEntityRotation (int client_fd, int id, uint8_t yaw, uint8_t pitch);
+int sc_damageEvent (int client_fd, int id, int type);
+int sc_setHealth (int client_fd, uint8_t health, uint8_t food);
 int sc_registries(int client_fd);
 
 #endif

src/main.c

@@ -105,6 +105,8 @@ void handlePacket (int client_fd, int length, int packet_id) {
         }
         sc_setHeldItem(client_fd, player->hotbar);
 
+        sc_setHealth(client_fd, player->health, player->hunger);
+
         sc_playerAbilities(client_fd, 0x01 + 0x04); // invulnerability + flight
         sc_updateTime(client_fd, world_time);
 
@@ -182,11 +184,12 @@ void handlePacket (int client_fd, int length, int packet_id) {
 
         double x, y, z;
         float yaw, pitch;
+        uint8_t on_ground;
 
         // Read player position (and rotation)
-        if (packet_id == 0x1D) cs_setPlayerPosition(client_fd, &x, &y, &z);
+        if (packet_id == 0x1D) cs_setPlayerPosition(client_fd, &x, &y, &z, &on_ground);
-        else if (packet_id == 0x1F) cs_setPlayerRotation (client_fd, &yaw, &pitch);
+        else if (packet_id == 0x1F) cs_setPlayerRotation (client_fd, &yaw, &pitch, &on_ground);
-        else cs_setPlayerPositionAndRotation(client_fd, &x, &y, &z, &yaw, &pitch);
+        else cs_setPlayerPositionAndRotation(client_fd, &x, &y, &z, &yaw, &pitch, &on_ground);
 
         PlayerData *player;
         if (getPlayerData(client_fd, &player)) break;
@@ -197,6 +200,18 @@ void handlePacket (int client_fd, int length, int packet_id) {
           player->pitch = pitch / 90.0f * 127.0f;
         }
 
+        // Handle fall damage
+        if (on_ground) {
+          int8_t damage = player->grounded_y - player->y - 3;
+          if (damage > 0 && getBlockAt(player->x, player->y, player->z) != B_water) {
+            if (damage >= player->health) player->health = 0;
+            else player->health -= damage;
+            sc_damageEvent(client_fd, client_fd, D_fall);
+            sc_setHealth(client_fd, player->health, player->hunger);
+          }
+          player->grounded_y = player->y;
+        }
+
         // Broadcast player position to other players
         #ifdef SCALE_MOVEMENT_UPDATES_TO_PLAYER_COUNT
           // If applicable, broadcast only every client_count-th movement update

src/packets.c

@@ -614,7 +614,7 @@ int cs_clickContainer (int client_fd) {
 }
 
 // C->S Set Player Position And Rotation
-int cs_setPlayerPositionAndRotation (int client_fd, double *x, double *y, double *z, float *yaw, float *pitch) {
+int cs_setPlayerPositionAndRotation (int client_fd, double *x, double *y, double *z, float *yaw, float *pitch, uint8_t *on_ground) {
 
   *x = readDouble(client_fd);
   *y = readDouble(client_fd);
@@ -623,38 +623,32 @@ int cs_setPlayerPositionAndRotation (int client_fd, double *x, double *y, double
   *yaw = readFloat(client_fd);
   *pitch = readFloat(client_fd);
 
-  // ignore flags
+  *on_ground = readByte(client_fd) & 0x01;
-  readByte(client_fd);
 
   return 0;
-
 }
 
 // C->S Set Player Position
-int cs_setPlayerPosition (int client_fd, double *x, double *y, double *z) {
+int cs_setPlayerPosition (int client_fd, double *x, double *y, double *z, uint8_t *on_ground) {
 
   *x = readDouble(client_fd);
   *y = readDouble(client_fd);
   *z = readDouble(client_fd);
 
-  // ignore flags
+  *on_ground = readByte(client_fd) & 0x01;
-  readByte(client_fd);
 
   return 0;
-
 }
 
 // C->S Set Player Rotation
-int cs_setPlayerRotation (int client_fd, float *yaw, float *pitch) {
+int cs_setPlayerRotation (int client_fd, float *yaw, float *pitch, uint8_t *on_ground) {
 
   *yaw = readFloat(client_fd);
   *pitch = readFloat(client_fd);
 
-  // ignore flags
+  *on_ground = readByte(client_fd) & 0x01;
-  readByte(client_fd);
 
   return 0;
-
 }
 
 // C->S Set Held Item (serverbound)
@@ -797,6 +791,7 @@ int sc_teleportEntity (
   return 0;
 }
 
+// S->C Set Head Rotation
 int sc_setHeadRotation (int client_fd, int id, uint8_t yaw) {
 
   // Packet length and ID
@@ -810,6 +805,7 @@ int sc_setHeadRotation (int client_fd, int id, uint8_t yaw) {
   return 0;
 }
 
+// S->C Set Head Rotation
 int sc_updateEntityRotation (int client_fd, int id, uint8_t yaw, uint8_t pitch) {
 
   // Packet length and ID
@@ -826,6 +822,34 @@ int sc_updateEntityRotation (int client_fd, int id, uint8_t yaw, uint8_t pitch)
   return 0;
 }
 
+// S->C Damage Event
+int sc_damageEvent (int client_fd, int entity_id, int type) {
+
+  writeVarInt(client_fd, 4 + sizeVarInt(entity_id) + sizeVarInt(type));
+  writeByte(client_fd, 0x19);
+
+  writeVarInt(client_fd, entity_id);
+  writeVarInt(client_fd, type);
+  writeByte(client_fd, 0);
+  writeByte(client_fd, 0);
+  writeByte(client_fd, false);
+
+  return 0;
+}
+
+// S->C Set Health
+int sc_setHealth (int client_fd, uint8_t health, uint8_t food) {
+
+  writeVarInt(client_fd, 9 + sizeVarInt(food));
+  writeByte(client_fd, 0x61);
+
+  writeFloat(client_fd, (float)health);
+  writeVarInt(client_fd, food);
+  writeFloat(client_fd, 5.0f); // saturation
+
+  return 0;
+}
+
 // S->C Registry Data (multiple packets) and Update Tags (configuration, multiple packets)
 int sc_registries (int client_fd) {
 

src/tools.c

@@ -237,6 +237,8 @@ int reservePlayerData (int client_fd, uint8_t *uuid, char *name) {
       player_data[i].client_fd = client_fd;
       memcpy(player_data[i].uuid, uuid, 16);
       memcpy(player_data[i].name, name, 16);
+      player_data[i].health = 20;
+      player_data[i].hunger = 20;
       player_data[i].y = -32767;
       return 0;
     }