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Map File Format

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I just started experimented with tile based games and I am writing a level editor. Right now I am just using a 2d array of integers to store the id of all the tiles. That works great, but how do I store entitites like teleports to other maps (doors), enemies and other NPCs ?

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There are two schools of thought on this:

1) Make the entities tiles themselves. Upside: easiest to implement. Downside: moving entities have issues as far as what is underneath them...nothing.

For example, teleporters. If you are using int''s (32-bits), use the low 16 bits for your item/tile ID, and use the high 16 bits for an X/Y destination.

2) Have a seperate data structure for entities. Upside: more flexible, can extend easily. Downside: added layer of complexity.

For example, create a linked list of entities. Every time you or another entity moves, check the positions of all of the entities in the linked list.

How would I store them? Personal preference: store the map in one file, entities in another, or use a PAK-style file format and combine them that way. I come from a testing background, and I''ve seen too many instances where when too much stuff was combined into a single file, and a change to one area had wide-ranging effects on others.

RomSteady - Able to leap off tall buildings in a single bound

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You could have an identifier (byte) for each special type you want to safe

  enum Specials { ID_TELEPORT, ID_ENEMY, ID_NPC, NO_MORE_SPECIALS };class Teleport {  //...  char getType() const {    return ID_TELEPORT;  }}class Npc {  //...  char getType() const {    return ID_NPC;  }}

Then when you want to write the objects, just use something like

  template<typename T>void writeObject(const T& object) {  writeByte(object.getType());  writeInt(sizeof(object));  //writes all bytes from the object, one by one  writeAll(&object, sizeof(object));}//somewhere else:{  Teleport teleport1;  Npc myNpc;  writeObject(teleport1);  writeObject(myNpc);  //use a loop to write all the stuff from the editor :D  writeByte(NO_MORE_SPECIALS);}

And when you want to read them:

  while(true) {  char identifier = readByte();  if (identifier == NO_MORE_SPECIALS) break;  int sizeOfNewObject = readInt();  void* memoryForNewObject = reinterpret_cast<void*>(new char[sizeOfNewObject]);  //reads sizeOfNewObject amount of bytes one by one and stores them to memoryForNewObject  readAll(memoryForNewObject, sizeOfNewObject);  switch (identifier) {    case ID_TELEPORT:      addTeleport(reinterpret_cast<Teleport*>(memoryForNewObject));      break;    case ID_NPC:      addNPC(reinterpret_cast<Npc*>(memoryForNewObject));      break;  }}

I have NO idea if it works and it''s probably not a very good way to save objects.. At least it looks pretty ugly. But I just felt the urge to write something :D

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Oh yah, I forgot to mention... If you want a safer method which needs more writing, try this:

  class Teleport {  //...  void writeMe() {    writeByte(ID_TELEPORT);    writeInt(x); //x, y coordinates and so on    writeInt(y);  }  void readMe() {    readInt(x);    readInt(y);  }}//somewhere else{  teleport.writeMe();  writeByte(NO_MORE_SPECIALS);}

  while(true) {  char identifier = readByte();  if (identifier == NO_MORE_SPECIALS) break;  switch (identifier) {    case ID_TELEPORT:      Teleport* teleport = new Teleport();      teleport->readMe();      addTeleport(teleport);      break;    case ID_NPC:      Npc* npc = new Npc();      npc->readMe();      addNpc(npc);      break;  }}

That way you need to write writeMe() and readMe() functions for all object types.. But if your objects contain pointers, then you must do it this way.