Those blue and red rez triangles... how do I kill them?

Returning SLer here, I get back and all of a sudden my screen is covered in these blue and red traingles that appear for a few seconds every time an attachment rezzes (at least I think that's what it is...).
So if I go into a crowded area, my screen is a blur of blue and red... please, how can I turn this off? It's incredibly annoying and very immersion breaking.

Control-Alt-Shift-U

You have just had more positive impact on my SL experience than anyone, since the very beginning.
THANK YOU!

Obviously.

In the event it's easier to remember the menu option, it's on the Advanced menu, named "Show Updates".

The colors appear when objects require sending out information from the servers to our viewers. The different colors show differing amounts of information. It can be used to give some idea of what objects are slowing things down to what degree.

It doesn't cause client side slow-down though.

Each "cone" represents an object update (red = full ; blue = partial ; green = delete) which you'll receive for everything with draw distance whether you can currently see it or not.

In all but extreme cases it's not going to cause actual slow down, although it can cause network saturation on either sim or client side.

People on an ISP with a transfer limit in particular should keep an eye out (I've seen scripted objects causing a constant near 1Mbit/s stream of object updates) since it's going to munch up bandwidth even more than textures will if you hang around for a while (in the broad sense of having the object within your draw distance). (In View / Statistics Bar you can expand Network to see what the bandwidth bar in the upper right corner represents: it'll usually be either textures or objects for the most part)

It's useful for scripters as well, since anything that's sending out constant object updates is more than likely badly scripted.

(Temp rezzers are "evil" for the same reason: they cause a full object update to be sent per prim of whatever it is they're rezzing followed by a delete a minute later and do so constantly)

I think that's changed fairly recently. I know my FPS totally tanks now when I enable show updates - it didn't do that, say, 6 months ago..

I meant the object updates themselves don't necessarilly cause lag though .