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Adrian Bibby Walther

OpenGL
glTexImage2D does nothing

12 posts in this topic

I'm using SDL_image to load textures for my game, I then try to load them into OpenGL using glTexImage2D.

Using the following code I've found out, that the problem lies in glTexImage2D, as it simply does nothing. (at least the width and height of the texture remains unchanged)
[CODE]
int ID,Width,Height;

glGetIntegerv(GL_TEXTURE_BINDING_2D,&ID);
glGetTexLevelParameteriv(GL_TEXTURE_2D,0,GL_TEXTURE_WIDTH,&Width);
glGetTexLevelParameteriv(GL_TEXTURE_2D,0,GL_TEXTURE_HEIGHT,&Height);

std::cout << ID << ": " << Width << "*" << Height << std::endl;
[/CODE]

The weird thing is that I have another program, and it uses the exact same code, but it works in that program.

glGetError returns 0 ie no error.

The code loading the texture and all is compiled and linked into a static library, and I have a test project that links with it, so I can see, if the code I've written works or not.
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Here you go:
[CODE]
Clear();

SDL_Surface *Surf = IMG_Load(File.c_str());

if(!Surf) return false;

GLenum Mode = GL_RGB;
if(Surf->format->BytesPerPixel == 4){
Mode = GL_RGBA;
}

Width = Surf->w;
Height = Surf->h;

glGenTextures(1,&Tex);
glBindTexture(GL_TEXTURE_2D,Tex);

glTexImage2D(GL_TEXTURE_2D,0,Mode,Width,Height,0,Mode,GL_UNSIGNED_BYTE,Surf->pixels);

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

int Min,Mag;

glGetTexParameteriv(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,&Min);
glGetTexParameteriv(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,&Mag);

SDL_FreeSurface(Surf);

glBindTexture(GL_TEXTURE_2D,0);
[/CODE]
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Have you checked to make sure that the GL context is valid and initialized?
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Check your width and height to make sure that they're powers of two if you have older hardware that doesn't support non-power-of-two textures. Also given that you're using GL_RGB formats you should be setting your glPixelStorei parameters appropriately.
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[quote name='mhagain' timestamp='1337908108' post='4943087']
Check your width and height to make sure that they're powers of two if you have older hardware that doesn't support non-power-of-two textures. Also given that you're using GL_RGB formats you should be setting your glPixelStorei parameters appropriately.
[/quote]

If it is a power of 2 problem, then glGetError() would return something other than GL_NO_ERROR.
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I'm not sure, but shouldn't glTexParameters be called before glTexImage2D? Maybe that fixed it?
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[quote name='Sponji' timestamp='1338143292' post='4943764']
I'm not sure, but shouldn't glTexParameters be called before glTexImage2D? Maybe that fixed it?
[/quote]

No, it doesn't matter of you call it after or before.
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Turns out I only fixed the code for "power of 2"-textures.
My graphics card does support GL_ARB_texture_non_power_of_two, and in my other project it worked absolutely fine.
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[quote name='Somone else' timestamp='1338239010' post='4944138']
Turns out I only fixed the code for "power of 2"-textures.
My graphics card does support GL_ARB_texture_non_power_of_two, and in my other project it worked absolutely fine.
[/quote]

Are you sure glGetError doesn't detect any problems?
Also, what is your GL version?
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[quote name='V-man' timestamp='1338384608' post='4944664']
Are you sure glGetError doesn't detect any problems?
Also, what is your GL version?
[/quote]
This time, errors did appear.
I traced (due to the lack of a better word) it back to the SDL OpenGL configuration: I apparently didn't enable SDL_GL_MULTISAMPLEBUFFERS.

~Solved
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