Fulldome refers to immersive dome-based video projection environments. The dome, horizontal or tilted, is filled with real-time (interactive) or pre-rendered (linear) computer animation, live capture images, or composited environments (which is a combining of visual elements from separate sources into single images). Although the current technology emerged in the early-to-mid 1990s, fulldome environments have evolved tremendously in the the last few years from numerous influences, including immersive art and storytelling, with technological roots in domed architecture, planetariums, multi-projector film environments, flight simulations, and Virtual Reality (VR), and Augmented Reality (AR).
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Video Technology
Fulldome video projection can use a variety of technologies in two typical formats: single- and multiple-projector systems. The individual projector(s) can be driven by a variety of video sources, typically feeding material rendered in either real-time or “pre-rendered” modes. The end result is a video image that covers an entire domed projection surface, yielding an immersive experience that fills a viewer’s field of view.
Single and Multiple Projector Systems
Single-projector fulldome video systems use a single (or mixed) video source displayed through a single fisheye lens, typically located at or near the center of a hemispherical projection surface. A single projector has the benefit of avoiding edge blends between multiple projectors. The main disadvantage of single fisheye systems is that they are limited to the resolution of one projector, and in the smallest dimension of the video image to cover a full dome. Another disadvantage of central projectors is the loss of the center of the dome for optimal viewing of the reconstructed perspective view provided by true hemispheric projection, a problem shared with traditional planetarium projectors. However, this disadvantage fades as audience size increases (everyone cannot be at the center of the dome anyway).
Single-projector mirror systems, pioneered by Mirrordome from Swinburne, but now offered by a plethora of manufacturers, are placed on the edge of the dome to increase seating, decrease costs, and to allow analog planetariums to become digital without giving up their star projector. It is also possible to build such a system at relatively low cost. The main disadvantage is noticeably lower projection quality compared to purpose-built lenses, despite being able to project a higher proportion of the projector resolution.
Multiple-projector fulldome video systems rely on two or more video projectors edge-blended to create a seamless image that covers a hemispherical projection surface; splitting the entire image up into segments allows for higher-resolution imagery and projector placement that does not intrude on the viewing area underneath the dome. A disadvantage of multiple projection is the need to frequently adjust the alignment of projectors and the uneven aging of separate projectors leading to brightness and color differences between segments. Even minor performance differences between projectors can be obvious when projecting a solid color across the entire scene. Edge blended areas where projectors overlap often have some smearing, double images, and can have very obvious additive black level areas if poorly designed or configured.