The Full Dome Saga Part 1: From Mechanical to Digital
Hello Readers, you are about to embark on a journey through the world of planetarium technology and production. Every Friday for the next few weeks we will explore all things digital planetarium. The first part of the Full Dome Saga is a brief background on the technological evolution from the traditional planetarium to the digital dome of today. In later posts we will compare production techniques and equipment used for Hollywood movies to that used for planetarium production, animation and rendering techniques, live action capture, and more.
When many people think planetarium, they imagine a dark, domed room with a strange machine in the center. They imagine a mystifying experience where a presenter takes them on a tour of the stars and constellations in our sky. In the last ten years, the digital revolution has taken the planetarium on an interesting journey (which is far from over). With advances in digital projection systems, software and computers, planetaria are transforming into immersive theaters. Using anywhere between one and thirty projectors, a bank of synchronized computers, and sophisticated software, planetaria are pushing the boundaries of possibility for both education and entertainment.
These digital systems allow presenters to move beyond the traditional night sky star talk. In a digital planetarium you can watch a full dome movie, specially produced to cover the entire dome, providing a “you are there” experience unlike any other. Differing from traditional movie theaters, digital planetaria possess realtime astronomy visualization software. A presenter can simulate and navigate through actual astronomical data in real time, almost like a video game. Full dome content is still largely CGI, with only small amounts of live action. Where are the IMAX type nature films designed for the immersive planetarium theater experience? They’re coming…. (I hope!)
Here at LASM the Irene W. Pennington Planetarium houses a 4k digital projection system made by a company called Sky Skan. Our image on the dome is created by two projectors (one at the front and the other at the back of the dome). There are four computers sending visual information to each projector, and one computer that stores the surround sound (see picture at left). All of the computers are controlled by a main master computer and a software called Digital Sky and SPICE. In order for everything to run seamlessly (no pun intended) all computers must run simultaneously with no lagging.
Why are there so many pieces? Projecting a 4k video at a normal frame rate requires multiple computers to share the job, each one takes a small piece of the video to send to the projector (allowing everything to run quickly and smoothly). Current projector technology makes it difficult and expensive to cover a large 60-foot dome with a high quality image using a single projector, so we use two. Other planetaria use four, six or more to accomplish this task.
What does 4k even mean anyway? And does frame rate matter? Return next week to learn about how projection and video in the planetarium compares to your HD TV…