Portal 1 BTS
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The original Portal does not have as many themes as Portal 2, there is only normal test chambers and Behind The Scenes (BTS). Portal 2 on the other hand, has many themes. This article will talk about how to make BTS in the original Portal.
In many maps with this style there are catwalks, vac tubes, wall pipes, deceptive skyboxes, and more.
The textures for this are very simple, for metal walls and ceilings, add metal/metalwall_bts_006a. For a metal floor, add metal/metalfloor_bts_001a, or metal/metalfloor_bts_001b. For concrete walls, add concrete/concrete_bts_modular_wall001a, concrete/concrete_bts_modular_wall001b, concrete/concrete_bts_modular_wall001c and concrete/concrete_bts_modular_wall001d. For a concrete ceiling, add concrete/concrete_bts_ceiling002a. And finally, for the floor add concrete/concrete_bts_floor002a.
To create flat catwalks, first make the frame for it by using the texture metal/metalbeam_bts_001a in a 4 x 4 x 4 brush. Next, fill it in with either metal/metalfloor_bts_001b or metal/metalstair004b with the height as 1.
To create stair catwalks make a frame with the texture metal/metalbeam_bts_001a with a 4 x 4 x 4 brush, then rotate it 45 degrees. Finally, make grated stairs with 1 height and 16 length across the frame with the texture metal/metalstair004a.