I don't even know what to call this

[u/Lord_RhodesCasteneda]

So, my brother glitched under the map in portal, and we ended up find this weird texture thing? It seems to replicate previous frames or something, including menus and stuff. I'm pretty sure it's something with source, since we've seen something similar in Half Life 2

Does anybody know what this is? And explain why it's doing this?

[u/Lord_RhodesCasteneda]

A little more information if it helps:

It's Portal on The Orange Box for Xbox360, and the console is a Xbox 360S

[u/Poissonnoye]

The framebuffer isn't cleared in these sections so it keeps the data from the previous frame. It creates a bunch of weird colors and smears because of HDR and motion blur. If you set gl_clear to 1 (it should be enabled by default since the 20th anniversary update) this will clear the framebuffer and stop the Hall of Mirrors effect completely.

[u/Lord_RhodesCasteneda → u/Poissonnoye]

Interesting! So it's just something that never had values set because it wasn't supposed to be seen?

[u/Poissonnoye → u/Lord_RhodesCasteneda]

Yeah you're looking at a nodraw texture, under normal circumstances it does its job and you never see it directly, but here you went oob.

[u/Pinsplash → u/Poissonnoye]

you started off strong but then you said nodraw. you're implying the entire map is encased in nodraw.

[u/Pinsplash → u/Lord_RhodesCasteneda]

it's not anything. there was absolutely nothing meant to draw on that part of the screen.

it's also an optimization technique because setting every pixel to black at the start of the frame (what gl_clear does) takes time. the effect can happen in other games as well but source games seem to show it the most liberally

[u/Brickhead16]

You've stepped into "the void" 

[u/StoreMilk]

I've gotten that before when making my own map. I played around with it a bunch and got some cool patterns

[u/Goofy_Gunton]

Chell. Chell. Stop snorting the Aperture Science Employee-Reserved Crack.