The bug
All textures of blocks with 3D models and items have gaps at the corners.
How to reproduce
This can be seen with doors (see screenshots)
You can see the problem better if you use a resource pack using "3D" blocks, such as Default 3D Models by Sibsib92 v0.97
You can also see it pretty easily when you just hold a tool like a pickaxe in your hand
Examples
Look at the screenshots below.
Linked issues
is duplicated by 55
relates to 2
Attachments
Comments 67
The right screenshot is the default texture pack (the one with the door and the sky in the background) 🙂
Can confirm this is most likely NOT a driver issue, I have an nVidia GTS 450 with graphics driver version 346.47.
This is called UV bleeding... properly sized blocks and items pull the very edge texture, in the cases shown in your screenshots that is transparent. However, if the pixels just outside the used textures are very different (like bright red) it is very noticeable.
So no, this is not a resource pack problem, but one with the model system. UV bleeding occurs by default on even precise models, the only way to fix it is to shrink UV coords very slightly or to surround your texture with a bleed area so when pixel bleeding occurs, it pulls the color from there so it's the right color.
This is especially easy to notice when blocking with a sword (using the blocks_attacks component).
Please switch to the default resource pack and see if it occurs there.