# Bug LaTex oddness

1. Jan 3, 2009

Staff Emeritus
If you check out https://www.physicsforums.com/showthread.php?t=282332", you'll see some LaTeX strangeness.

Specifically, not all the images appear, and the ones that do appear seem not to match the LaTeX source. It's almost as if the images are offset: i.e. the n-th bit of source ends up displayed at the (n+3)-th slot.

Last edited by a moderator: Apr 24, 2017
2. Jan 3, 2009

### Gokul43201

Staff Emeritus
Testing: $\nu_\mu,~\nu_{\mu}$

$$\nu_\mu,~\nu_{\mu}$$

Seems to be okay here. Can't think of anything obvious that would do this just there.

PS: You should try inline $\LaTeX$ for little bits in the middle of a sentence/paragraph.

3. Jan 4, 2009

### Redbelly98

Staff Emeritus

You might try editing your entry that has the odd LaTex, and then SAVE it without actually changing anything. At least, that trick worked on a different bug that occurred in the PF Library ... see my comment of Jan1-09 here:
https://www.physicsforums.com/library.php?do=view_item&itemid=25

4. Jan 4, 2009

Staff Emeritus
Redbelly. I just did that. It looks the same, I'm afraid.

5. Jan 4, 2009

### cristo

Staff Emeritus
It's because some of your tags were [TEX] and some were [tex]. For some reason, the software doesn't like this. I've amended them, and now it looks OK to me.

Last edited: Jan 4, 2009
6. Jan 4, 2009

Staff Emeritus
Thanks, Cristo.

How odd that upper case works and lower case works, but you can't mix them.

7. Jan 10, 2009

### HallsofIvy

Staff Emeritus
I've seen that happen when editing LaTex. Clicking the refresh button clears it up. Now, does anyone know why it is necessary to "refresh" when you when you have just saved an edit?

8. Jan 10, 2009

### Hootenanny

Staff Emeritus
When you submit a post containing latex tags the server recognises the tags and generates the latex output from your source. The output is saved as an image file with name corresponding to the post number and the equation number in that post: "[post number]-[equation number].png". So for example, if I were to create a latex equation in this post, it's file name would be "2029042-0.png". If I were then to create an additional equation, it would be named "2029042-1.png" and so forth.

Now once the server has created the image, it replaces the latex source in your post with the URL of the latex image. When you click edit the server then replaced the latex image with the latex source so you can edit it. Now, when you edit a latex equation and click save, the server re-generates the latex image and overwrites the existing latex image file; so if I were to edit the equation corresponding to "2029042-0.png" then the new latex image also be called "2029042-0.png" and would replace the old file.

Unfortunately, the way VBulletin is coded means that when you click save, only the text in your post is refreshed, meaning that you will be viewing cached images. This is good in one respect in that you don't have to waste bandwidth re-downloading images if you simply want to edit a post, however bad in another respect if you have edited a latex image.