Textures do not show up properly on my computer

OpenGL OpenGL: Basic Coding
1

I am having a problem with textures in an opengl class I am taking. When the textures show up they are distorted and unrecognizable. I know the textures should be working as they do on other computers. I think it might be related to my graphics card. I am using Win2k, glut, and have an ATI Rage Mobility 128 graphics card (older laptop).

2

Hi Shishka55,

I would suggest posting the code, so we can see what’s going on, so we can discount the possibility of programmer error :wink:

3

graham is right, post the code here, because maybe this is simply an error in vertex texturing coordinates

4

Ok, but this isn’t my code… it was written by a teaching assistant for my class, so please do not steal it!!

deleted since its not mine

The thing is, it seems to work on other computers, just not mine, thats why I wonder if its an issue of graphics card compatibility.

5

For texture enviornment, try this:

glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE );

6

Well, I don’t see anything wrong with the code you posted. Though, without seeing all of the code, it’s difficult to make a determination.

You might try setting glPixelStorei( GL_UNPACK_ALIGNMENT, 1 ). The wrong alignement can lead to trash in your textures.

Otherwise, take a simple texture demo that you know will work, and go from there. Try to get the texture demo in the RedBook to work, for example.

http://fly.cc.fer.hr/~unreal/theredbook/chapter09.html

If you discover that basic texturing is working, you then know that the problem is elsewhere.

I hope this helps.

7

Originally posted by shishka55:
[b]

	//copy image data to texture
	if(bpp == 32)
		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_BGRA_EXT, GL_UNSIGNED_BYTE, &filedata[18]);
	else
		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_BGR_EXT, GL_UNSIGNED_BYTE, &filedata[18]);

[/b]
1.) You should check if GL_BGR_EXT and/or GL_BGRA_EXT is supported by the Rage 128.
I think GL_BGRA_EXT is supported but I am unsure about GL_BGR_EXT.

2.) In case its a 24 bit image the internal format should be set GL_RGB8 and not GL_RGBA8.

8

Hi Honk,

It is a good idea to check for extension support. Here’s a great site for this very thing:
http://www.delphi3d.net/hardware/listreports.php

And, as always, be sure to check your extension string.

In the case of EXT_bgra, both the BGR_EXT and BGRA_EXT enumerants are included.

There’s no requirement that states that a RGB source format must be matched by a RGB internal format. Granted, the symmetry is pleasing :slight_smile:

[edit: format]

9

thanks for all the help so far… i tried a few of the solutions but nothing has seemed to work yet. However, I did figure out a little more about the problem. Its occuring when I use textures that are larger than the surface and have to be shrunk. If I stretch a smaller texture it works, and if I only used a fraction of the larger texture so it does not have to be shrunk down it works fine. I do still get some weird blurry texturing on the sides that are almost out of view on a rotating object.

10

I just noticed that the code you posted uses the SGIS_generate_mipmap extension. This extension is supported only on Radeon or Geforce cards, but not on a Rage.

You can either replace the glTexImage call by a gluBuild2DMipmaps call, or turn mipmapping off completely (set the MIN_FILTER to GL_LINEAR instead of GL_LINEAR_MIPMAP_LINEAR).

11

Thank you so much Overmind… that fixed it! I am so glad you guys were able to help me. I am still new to this and this texture issue has been bothering me for awhile. Thanks.