# OpenGL [PyOpenGL] Textures stop working when I use glGenTextures()

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I have a pretty solid background of OpenGL in C++, but I'm not nearly as used to it in Python. I'm using PyOpenGL as the binding. I'm also using PyGame. My problem is odd in that it doesn't work when I do things 'correctly', and mostly works when I make a blatant mistake! When I started this program, I accidentally forgot to call glGenTextures(1) and just initialized my texture to 0. Since I only had one textured object to begin with, it worked fine. The texture loaded, displayed, blended, etc. properly. Then I added a second textured object and noticed my mistake since they were both given the same texture. I corrected by mistake, but now no textures work. The quads simply come up as white rectangles, as if they hadn't been textured at all. Now I know that loading, binding, etc. worked just fine since it worked when I didn't call glGenTextures(), so that has left me with just one place where it's gone wrong, the actual call to glGenTextures! But how could I have messed that up? Check out my Sprite class below.
class Sprite:
def __init__(self, x,y, w,h, fileName):
self.x = x
self.y = y
self.w = w
self.h = h

self.fileName = fileName

glEnable(GL_TEXTURE_2D)

texData = pygame.image.tostring(self.img, "RGBA", 1)

#Bind it to a texture
self.texture = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, self.texture)
width = self.img.get_width()
height = self.img.get_height()
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, texData )

def Draw(self):
glBindTexture(GL_TEXTURE_2D, self.texture)

glPushMatrix()

glTranslatef(self.x, self.y, 0.0)

glColor3f(1.0,1.0,1.0)
glEnable(GL_TEXTURE_2D)

w = self.w / 2.0
h = self.h / 2.0

glTexCoord2i(0,1)
glVertex3f(-w,h,0.0)

glTexCoord2i(1,1)
glVertex3f(w,h,0.0)

glTexCoord2i(1,0)
glVertex3f(w,-h,0.0)

glTexCoord2i(0,0)
glVertex3f(-w,-h,0.0)

glEnd()

glPopMatrix()

If I replace the line "self.texture = glGenTextures(1)" in Sprite.__init__ with "self.texture = 0", then the texture is drawn fine! But then I get my previous problem where all textures turn out the same. I'm kinda ashamed that I'm having this problem, since it seems at first to be so basic, but I'm at a loss as to what to try. Hopefully a fresh perspective will notice my mistake quickly. Please tell me what I should do! Thanks for any help.

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I know this isn't the solution you wanted, but why not track texture names yourself?

You don't have to call glGenTextures() in order to use textures, it just takes the work out of tracking texture names.

So in your second texture, rather than having 0, use 1, etc...

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Can you really? I guess I had sorta known that (since it worked when I just used 0), but figured it wasn't a safe bet. I'll try using that until/unless I can get the 'proper' solution.

Thanks. :D

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what does glGenTextures(1) return?

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Ah interesting. I just used the above suggestion, but there's still a problem. The textures only work when I their number is 0. No others work. So the first texture that was loaded loaded fine, but all future textures just came up blank like before. I've checked and I am calculating the correct numbers (that is, 0,1,2... etc.)

And the plot thickens.

Edit: glGenTextures(1) returns first 1 and then 2. Hmm. When I run it outside of my program (aka: just inside of the python shell), it generates 'random' large numbers.

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Default texture minification filter requires a full mipmap set, but I don't see you either change it or loading a complete mipmap set. Load the rest, or set the minification filer to a non-mipmap filter.

Texture name 0 disables the texture object mechanism, and goes back to the old non-object texture mode from OpenGL 1.0 I think it was. I believe that default filter mode is non-mipmapped, so it works.

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Thanks! That was the problem. I hadn't know that before, but all my previous code I had accidentally disabled it just because I wanted GL_LINEAR instead, so it had never been a problem until now.

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