[RESOLVED] Multidimensional Array

I´m messing around a bit with procedurally generating terrain for a game I´m working on. The terrain itself is simply represented by a 2 dimensional array which containts height values, basicaly a heightmap.

The problem for me is, how do I implement this array. The array will be accessed and written to thousands of times in several loops and algorithms.

The test code I had written used a simple 2 dimensional array (float[][]). But I need a way to determine the size of the array in the constructor of the Terrain object, and this isn't possible when I have to determine the size of the array when I declare it.

So I tried a vector<vector<float>> setup. I have always used vectors over arrays in my code, and they have never cost me much performance wise. But when I used it here it slowed things down noticably. Perhaps it is because I have never extensivly accessed a vector of vectors before like I am trying now.

At the moment I have another solution and my situation looks a bit like below (psuedocode):

Code:

---


Class Terrain
{
        float* terrainArray;
        Terrain(int lenght, int width)
        {
                terrainArray = new float[lenght*width];
        }

};

---

This is currently working fine for me. But I don't think its the best solution, because everytime I access or write to the array, I need to do it like so terrainArray[lenght*width]. Personally I would like to see stuff like terrainArray[lenght][width] or even terrainArray.set(lenght, width, value). Perhaps I am nitpicking and I should simply keep using the current implementation. But there are some other options that I am considering and I would like some second opinions on the matter.

The current options I'm considering:

- Keep using float* terrainArray = new float[lenght*width]
- Write a thin wrapper class (called Array2D) around float* terrainArray = new float[lenght*width] to add some syntactic sugar.
- Use a well known library such as boost::multiarray (I don't know about its performance versus a vector or my personal solution)

Keep it constructive please, I don't consider myself a C++ veteran or anything. Do feel free to suggest other options as well.

Write a subscript operator and abstract away the 1 dimension into 2.

http://www.parashift.com/c++-faq-lit...html#faq-13.10
(this is only 90% on topic, but contains the gist of it)

Once you write operator()(int i, int j), then you terrain is a 2D array for all intents and purposes.

Take a look at the following FAQ that provides a two-dimensional array including random access via the subscript operator ([]).

Performance-wise it should pretty much match your C implementation if used correctly. Keep in mind that 'vector' allocates memory as it goes which certainly can hurt performance. You can use 'reserve' to alleviate this issue though.

Thanks for the advice guys, you both pretty much suggest the same thing, which is what I ended up going with. It seems fine performance wise now, even if I do something ridicilous like make the array 20000x20000.