Graphic issues with Intel HD 4000
Solution 1:
Let me guess: the issue appeared with the 10.10.3 update? Well, then I am 98% certain it is a bug in OS X Yosemite. Your issue is related with this one.
Users report erratic kernel panics and some users have graphics glitches like you. The only common feature is having a Intel HD 4000 GPU.
On MacBook Pros with dual GPU you can avoid the problem by disabling Automatic Graphics Switching (System Preferences > Energy Saver).
Please contribute to the thread in the apple discussion forum and file a bug report (with link to the thread).
Solution 2:
What you describe in the post and the comments is definitely a dying GPU.
I am deeply sorry for your loss.
#AlsoLostAGPUOnMyMac
Solution 3:
Hi I believe it's not a dying GPU because we have same issue in all our MAC's.
It started after Yosemite upgrade.
https://www.dropbox.com/s/n04b4tmbbggkftd/wierdvideoproblem.mp4?dl=0
It may be Little Snitch. I disabled network traffic activity monitor, because glitch update pattern is like a data transfer pattern.
I'll post updates.