This is another issue that becomes regular in AutoCAD 2015. I saw this in Autodesk forum and get an email asking about this.
See the screen below. It’s like a spider is lost inside of AutoCAD and creating webs.
This image is taken from Autodesk forum topic here. The diagonal lines were never drawn, and not supposed to be visible.
This is obviously a graphic card issue. In most cases, turning off the hardware acceleration can fix this.
To turn off graphic acceleration, type GRAPHICSCONFIG then enter. Click the on/off switch.
It should fix the issue, but it will be much slower. Some of us manage to fix this by updating the graphic card drivers. Check if you already have latest graphic card.
You can also try to keep the hardware acceleration on, and try to turn off some visual effect options.
Is this issue specific to AutoCAD/LT 2015?
I don’t think so. I saw the same issue several years ago.
Basically we can use almost any graphic card to work with AutoCAD. But not all of them will work well with hardware acceleration. This is why certified hardware is important.
Certainly, we can work with hardware acceleration turned off. But when your drawing becomes complex, the performance won’t be good.
It’s a good idea to check certified hardware before you purchase one. For Autodesk product, you can see the list here: autodesk.com/hardware.