Hello all!

I am working on a 2D Tile Engine and I am trying to store the whole map in memory. The map is just ID's for tiles. Since my map is 4096*4096 tiles big, I am trying to store an array of 4096*4096 chars. When I try to compile the code that stores the chars, I get this error:

 error: cannot convert ‘uint8 (*)[4096] {aka unsigned char (*)[4096]}’ to ‘uint8* {aka unsigned char*}’ in assignment

And here is my code:

//Load all tiles into memory
   m_Tile = new uint8[MAP_WIDTH][MAP_HEIGHT];

//m_Tile is a protected variable in the map class( uint8 *m_Tile; )
//uint8 is type defined as an unsigned char.

Can someone please tell me what is going here? I can do this operation when I define uint8 as an int but not when its a char... :/

EDIT:

Doesn't work with int either.

I think you are assigning a pointer (that is an array) of arrays to a pointer. Notice the different types it says you are converting between?

error: cannot convert ‘uint8 (*)[4096] {aka unsigned char (*)[4096]}’ to ‘uint8* {aka unsigned char*}’ in assignment

From uint8*[] to uint8*.
Or, in another sense*, from uint8[][] to uint8[].

*Not technically accurate, but for illustrative purposes. [] is not identical to *, even if [] can convert to *.

It'd be easiest to just have it as a one-dimensional array that you treat like a 2D array:

m_Tile = new uint8[MAP_WIDTH * MAP_HEIGHT];
 
m_Tile[(y * MAP_WIDTH) + x] = blah;

[hr]

But why not use a one-dimensional std::vector so the memory is managed for you?

std::vector<uint8> m_Tiles(MAP_WIDTH * MAP_HEIGHT);

uint8 myClass::GetTile(unsigned x, unsigned y)
{
    return this->m_Tiles[(y * MAP_WIDTH) + x];
}

I think you are assigning a pointer (that is an array) of arrays to a pointer. Notice the different types it says you are converting between?

error: cannot convert ‘uint8 (*)[4096] {aka unsigned char (*)[4096]}’ to ‘uint8* {aka unsigned char*}’ in assignment

From uint8*[] to uint8*.
Or, in another sense*, from uint8[][] to uint8[].

*Not technically accurate, but for illustrative purposes. [] is not identical to *, even if [] can convert to *.

It'd be easiest to just have it as a one-dimensional array that you treat like a 2D array:

m_Tile = new uint8[MAP_WIDTH * MAP_HEIGHT];
 
m_Tile[(y * MAP_WIDTH) + x] = blah;

[hr]

But why not use a one-dimensional std::vector so the memory is managed for you?

std::vector<uint8> m_Tiles(MAP_WIDTH * MAP_HEIGHT);

uint8 myClass::GetTile(unsigned x, unsigned y)
{
    return this->m_Tiles[(y * MAP_WIDTH) + x];
}

Ohhh okay thankyou!! It compiles! And I just want to use dynamic memory because it is a bit quicker when I access it every draw call.

But now I have run into another problem, I wrote a program that generates tile IDs in the range of 0 to 1, but it is generating way more than I want. Can anyone tell me why? Here is my function:

//Little program to generate test map with only 0 and 1 tile

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <fstream>

using namespace std;

int main()
{
   ofstream file;
   file.open("default.vmf", ios::trunc);
   for (int j = 0; j < 4096; j++) 
   {
      for (int i = 0; i < 4906; i++) 
      {
         file << rand()%2;
      }
      file << '\n';
   }
   file.close();
   return 0;
}

So the file size should be (4096*4096) + 4096 == 16781312 right? Because I am filling up all the tiles and adding \n at the end of every 4096 tiles. But then after my program runs, the file is 20099072 bytes large. I don't understand what is happening here :/

EDIT: Just saw the problem.. I made a typo, 4906 instead of 4096 :p

Ohhh okay thankyou!! It compiles! And I just want to use dynamic memory because it is a bit quicker when I access it every draw call.

A) Optimizing prematurely causes more pain then it saves.

B) Unless you are running in debug mode, the speed of std::vector::operator[] should be about identical to a raw pointer's [] subscript operator.

C) If it's not identical, you could get the pointer to vector[0] (.data() in C++11) and treat it as a normal array anyway, but the dynamic memory will still be managed for you safely.

D) The C++ standard library is heavily optimized by the people who wrote the compiler you're using, I think it's rather fast enough.

To correct myself: if you are using C++11 (the latest version of C++ standardized last year), the correct container would probably be std::array<> or std::vector<>, but you might not have that available yet.

Alright guys now I feel as though I am going about this whole tile based game all wrong. Anyone have any suggestions on what I should do to make a top down tile based game? Any good engines out there that are cross OS (linux,win,mac)? I could make my own but I feel as though it would take too much time away from development of the actual game and I would just be reinventing the wheel. Or do you think that I should be trying to make my own TileEngine (never done it before)?

Thanks for all your suggestions so far guys!

-Brent