Problem in initializing any external object in displayfunc

[poliet]

Hi all!

I am a beginner and currently working on a little hobby Opengl game project and I am having several .h and .cpp files.

In my main.cpp file I have my glutDisplayFunc(renderScene). I would like to use a "ship" class that is declared in ship.h and the impemetation of the functions in consequently in ship.cpp. One of the constructors in ship.cpp Ship::Ship(string textures){...} takes a string in order to attach a certain texture to the object.

Since I wanted to have it all neat and nice, I use in main.cpp a func "initObjects" to initialize a ship object via Ship A("usethistexture"). This function initObjects is called directly in main.cpp from main{... initObjects(void);... }

I would like to use now this object A in my renderscene in main.cpp because in renderscene I use something something like

glBindTexture ( GL_TEXTURE_2D, A.itsTextures[0] );

The problem is, that since Ship A is initialized in initObjects it would get out of scope once it leaves initObjects and renderScene doesn't know Ship A therefore.

My first idea was to make the object external by trying something like in main.h and ship.h: extern Ship A;

but then I get a compiler error undefined reference to _A.

Anyway this seemed also strange to me to have all Objects being global.

Thus I tried to find an alternative and I found a solution which works but is pretty ugly.

I initialize the object Ship A in renderscene the first time the function is being called, since renderscene is an endlessloop. It works but the code looks ugly and i didn't manage to keep my promise in intitializing the object in initObjects().

Another thought then was I may pass A by reference to renderscene but this would be also pretty cumbersome to pass everytime an object to renderscene which is created in initObjects.

My last thought was then to make a new class in main.cpp which holds pointers to all objects. But this seems to me to be a lot of work and kind of exotic and if would declare this new class in newclass.h, I would face exactly the same problem as now.

I would be grateful for any suggestion how to have Ship A in the scope of renderscene in the cleanest possible way. Thanks.

Jack

[poliet]

Ok here is a strange thing. I sort of solved the problem...

When I write:

_main.cpp
#include stuff and all GL stuff
#include "ship.h"
..
vector <ship> vec;
int i
etc.
..
main {
Ship A("Texture t");
vec.push_back(A)
}

renderScene{
...
vec.DrawShip();
}

and everything works just fine and the textures get loaded and bound correctly.

However my first straight forward approach wouldnt work. It shows just a blank screen because the Texture doesnt get assigned but everything else and all other member data seems to be okay when I write

_main.cpp
include stuff and all GL stuff
#include "ship.h"
..
Ship A("Texture t");
int i
etc.
..

renderScene{
...
A.DrawShip();
}


Any suggestions why the second code wouldn't work? I use for my textures a tgaloader. The following two lines are in my Ship class constructor.

itsTexture = tgaLoadAndBind( "texture_t.tga" , TGA_COMPRESS )
and then I call
glBindTexture ( GL_TEXTURE_2D, itsTexture);