Going down, we can finally see the scaled-down 3D skybox geometry with a clearing for the playable area as rendered above (figure 7).įigure 7: The hidden 3D skybox geometry beneath the playable area. Turning around reveals the actual playable area on this level (figure 6).įigure 6: The playable area with and without the 3D skybox render layered behind it. The heavy fog makes them fit in without being too noticeable. Note how most of the buildings surrounding the main hospital building area are untextured gray polygons. Source games such as Half-Life 2 and Left 4 Dead 2 are well-known for using this technique (figure 4).įigure 4: Motion parallax in the first map ( apartments) of Left 4 Dead’s first campaign, “No Mercy”.Īttempting to leave the playable area results in a void (figure 5).įigure 5: Using noclip to move outside the playable bounds causes the 3D skybox to disappear. Let’s take a look at how this is done by first deconstructing an existing game.
These limitations include the camera draw distance limit, floating-point precision, and the general difficulty of working with large scales. They help overcome some of the limitations of actually having massive objects placed at large distances away from the world center. Figure 3: Outside the playable bounds.ģD skyboxes allow for much more dynamic scenery which can include moving parts and motion parallax if necessary, along with the ability to apply post-processing that’s easily limited to the skybox (by applying it using the second camera). Some games may opt to use a sphere, a hemisphere, or even a cylinder, but the intent and end result are almost always the same and the illusion of a vast world easily breaks once the player/camera leaves the intended bounds by any means, including glitches, “noclip”, and hacks (figure 3). This is ideal, of course, since a skybox is usually nothing more than 6 static images plastered on the faces of an inverted cube with the camera always at the center (figure 2). With or without any low-resolution props in between, they contribute to a sense of a much bigger world that’s so far away that it’s impossible to actually ever reach. To varying degrees, their counterpart in pre-rendered media (such as films and animations) would be the matte painting. In video games, a skybox provides an inexpensive far-away backdrop to the main playable area in which players are bound (figure 1). Note: If you just want to know how to get a 3D skybox working without the research stuff, skip to Part 2. In this tutorial we’ll be working on creating a 3D animated skybox as an extension of the static skyboxes you see in most Unity games.
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