How do you add the red/green lights on the door sensors as seen in 70s Aperture?

sp_a3_transition010000.jpg

it have its own model, I remember seeing it before but don't remember the name. (Altough idk if it have animations or such)

For glowing lights you generally want an env_sprite. Set the spawnflags to Start On. To make it transparent, you want to set the 'Render Mode' to either 'Glow' or 'World Space Glow'. Glow makes the sprite stay a constant size on-screen, whereas World Space glow makes it change size based on distance. See this comparison. Usually you want World Space Glow, but sometimes Glow is useful to draw the player's eye to a switch or similar thing. Set 'Scale' to control the sprite size, you probably want something like '0.05' for those small lights. Set a colour in Render Color. You can change the sprite used if you want. Input-wise, ShowSprite and HideSprite show and hide it. You can use the Alpha input to make it more transparent (0-255). Use Color to change the color of the sprite. You probably want to show and hide them in concert with the door animation.

A related entity is the env_beam, which displays a sprite stretched to form a line between two entities. It's good for lasers, lightning or similar things.

Thanks a lot. That was very helpful.