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glGenTextures

Started by cwhite Jan 21, 2005 at 11:09 PM 4 replies 4.4k views

Original Post

Jan 21, 2005 at 11:09 PM

What would cause glGenTextures to fail to return a valid texture identifier? For example, I have the following code in my project:

[source language=c++]
glGenTextures(1, &grassTex_);
if (!glIsTexture(grassTex_))
	cout << "OpenGL I curse at you" << endl;

The output of this snippet is "OpenGL I curse at you." I therefore, cannot use my grass texture. Any help would be greatly appreciated.

nts

115

nts

Jan 22, 2005 at 12:03 AM

dont you actually need to fill the texture with some data first before you can use glIsTexture? AFAIK it can only fail if you pass in a negative number or call it between glBegin and end.

If the handle returned isn't 0 then you are fine, just place some data in the texture first using glTexImage2D or gluBuild2DMipMaps

HTH

Myopic Rhino

452

Myopic Rhino

Jan 22, 2005 at 12:21 AM

A name isn't actually a texture object until you call glBindTexture() on it.

cwhite

Author

cwhite

Jan 22, 2005 at 1:03 AM

Thank you to both of you. I was using glIsTexture() to debug a program when the texture wasn't displaying. I thought I had found the reason, but now I see I have to keep looking. Moving the glBindTexture to before the glIsTexture() call made the glIsTexture() return true, but still didn't make my textures display

Myopic Rhino

452

Myopic Rhino

Jan 22, 2005 at 1:31 AM

Most common reason I see for that: You're either not loading mipmap levels, or you're not changing the minification filter from its default value, which is one of the mipmap modes.

cwhite

Author

cwhite

Jan 22, 2005 at 2:18 AM

Thanks again. I now have my terrain textured, so it's time to get lighting working.

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