static namespace members assignment SDL/OpenGL.

[stoffe1100]

Hello, i am working on my first semiserious project in c++ with SDL/OpenGL.

I have written a function that is supposed to load images using SDL_Image and convert them into usable gl textures.

I have a namespace which have some static members which are supposed to store the ID:s of the loaded textures.

When i am trying to assign any value to those unsigned ints nothing happends, they just stay zero for some reason. I cant even assign values using,
textures::TEXTURE_GRASS = 1;

What i find really strange is that they actually have the value 0, they should be unassigned.

The console output is:

The image: "grass.png" loaded succesfully and have the ID: 1
The image: "road.png" loaded succesfully and have the ID: 2
The image: "towerArrow.png" loaded succesfully and have the ID: 3
0
0
0

I will post the texture namespace and the function that loads images.


Here is the init function which initializes the whole game

bool game::Init()
{
	/*
            Some unrelated code that i removed for this topic.
        */

	//Initialize textures
	textures::TEXTURE_GRASS = functions::Textures::LoadTexture("grass.png");
	textures::TEXTURE_ROAD = functions::Textures::LoadTexture("road.png");
	textures::TEXTURE_TOWER_ARROW = functions::Textures::LoadTexture("towerArrow.png");
        

        //Just cout:ing the variables to check if they have a value
	std::cout << textures::TEXTURE_GRASS << std::endl;
	std::cout << textures::TEXTURE_ROAD << std::endl;
	std::cout << textures::TEXTURE_TOWER_ARROW << std::endl;

	return true;
}

Here is the LoadTexture function.

GLuint functions::Textures::LoadTexture( std::string filename)
{
	SDL_Surface * tempImage = IMG_Load(filename.c_str());
	SDL_Surface * image;

	if(tempImage != NULL)
	{
		image = SDL_DisplayFormatAlpha(tempImage);
		SDL_FreeSurface(tempImage);
	}else{
		std::cout << "Error: could not load " << filename << std::endl;
		return 0;
	}

	GLuint TextureID(0);

	glGenTextures(1,&TextureID);

	glBindTexture(GL_TEXTURE_2D,TextureID);

	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
	glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image->w, image->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, image->pixels);

	glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

	SDL_FreeSurface(image);

	std::cout << "The image: \"" << filename << "\" loaded succesfully and have the ID: " << TextureID << std::endl;
	return TextureID;
}

Here is the textures namespace

namespace textures
{
	static unsigned int TEXTURE_GRASS;
	static unsigned int TEXTURE_ROAD;
	static unsigned int TEXTURE_TOWER_ARROW;
}

[Peter87]

static here means that they will have internal linkage and each translation unit (source file together with all includes) will have it's own copy of the variables. What I think you actually want is to use extern declaration in the header

namespace textures
{
	extern unsigned int TEXTURE_GRASS;
	extern unsigned int TEXTURE_ROAD;
	extern unsigned int TEXTURE_TOWER_ARROW;
}

and define them in a source file

unsigned int textures::TEXTURE_GRASS;
unsigned int textures::TEXTURE_ROAD;
unsigned int textures::TEXTURE_TOWER_ARROW;

[stoffe1100]

I dont really understand how you mean But i will take a look at the extern keyword. will they still act global if i define them in a source file like that?

I have learned c++ totally on my own so i have missed alot of those basic stuffs and i have no teachers to ask if i hit a problem.

They teach us VB.NET i my school... And even non OOP VB.NET. so it's really bad.

My point was. It looks pretty dumb to use OpenGL when i dont even know the basics. Just wanted to point out why.

Thank you for your help!

[Peter87]

will they still act global if i define them in a source file like that?
Yes. If you define them in the header you will get "multiple definition errors" so you don't have much of a choice.

[stoffe1100]

okay. Does it matter where i define them?

[Peter87]

No. As long as they are defined once somewhere in any of the source files it should work.

[stoffe1100]

I am so happy right now when i saw it working i cant describe it. Thank you for you kindness again!

[stoffe1100]

Hmm, i ask this questing right here instead of starting a new thread. How can i acces all the pixels in the texture and raise them a bit? so that the texture will get more light?

EDIT: Or maybe is it better to just make some other textures. Feels like an ugly solution. But accessing pixels like that is very performance dropping right?