Env_sprites all messed up
I was testing out a concept I had in hammer, and ingame, the sprites appear like the pic I attached.
I tried verifying my game cache, and searching for help on the forum, I seem to be having this problem alone. in hammer, it shows the black outline as well.
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Did you set the render mode properly? 
It should probably be World Space Glow for what you want.
thanks! I never really knew about that whole thing, I can use my sprites again now! 
Aperture Science: We do our science asbestos we can!
Just a question: I was always using additive. What is the differnece to world space glow? should I better be using the last?
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Glow and World Space Glow are supposed to be better for sprites. I don't think there's much difference though.
"World space glow" means that the sprite will be scaled depending on the viewing distance.
If it's set to just "Glow", then it will always be the same size on the screen. (Somewhat like the purple origin handle in Hammer.)
As for which one is better: just try them both and choose the one you like best!
Other Portal 2 maps: Medusa Glare
Portal 1 maps: Try Anything Twice | Manic Mechanic
That's a good question. I quickly tried it out and it turns out that there is a difference:
Left is "additive", right is "world space glow".
If you look carefully, you can see that the "additive" one intersects with surrounding objects, while the "world space glow" one is rendered in front of everything. (As long as its centre is visible.)
Other Portal 2 maps: Medusa Glare
Portal 1 maps: Try Anything Twice | Manic Mechanic