5cam (Depreciated, see: Hemicam.)

A five camera cluster used in Blender for planetarium show production.

Each camera has a 90° field of view, with a 1:1 aspect ratio. The five camera angles are: left, front, right, up, and back.

TGA frame sets produced with a 5cam cluster can be converted to fisheye projections with Cube2Dome.

Pronounced: "scam" or "five cam."

Alpha

In digital media, a term referring to transparency -- specifically: variable transparency.

Alpha is an extremely important factor in digital graphics and video. Alpha allows the user to create very convincing composite images consisting of many layers.

PNG images support an alpha channel, where GIF images support only binary representations of transparency.

See: PNG.

Aspect Ratio

In digital media, a term referring to the ratio of width to height. This ratio is often based on projected image measurement and not pixel count, as pixels are not always square (television has rectangular pixels).

Examples: NTSC Broadcast Television 4:3, HDTV 16:9, Mediaglobe Video 1:1.

See: Pixel Aspect Ratio.

Blender

An open source 3D software used in planetarium show production.

Blender is a versitile and capable 3D platform that also offers video editing capability. In Ott Planetarium productions, Blender renders are often processed by the WRCRS cluster.

blender.org

Codec

A program that encodes and decodes a digital data stream. Often used to apply a compression algorithm to audio or video. Codec is short for Encode-Decode.

http://en.wikipedia.org/wiki/Codec

Compression

The process of encoding information into a smaller data volume. This becomes extremely important when dealing with large image sets (frames) or large amounts of audio.

Some compression algorithms are lossy (JPEG, TARGA, MP3), while others are lossless (PNG, FLAC). Some file formats are uncompressed (BMP, WAV). "Lossy" means that some level of detail is lost during compression. Lossless means that although data has been compressed, the compressed file contains the same level of detail as the original.

Try saving images in Photoshop using different compression algorithms and detail settings. Compare the quality and file size of your output with that of the original. Try listening to internet radio feeds at different data rates, compare the quality.

http://en.wikipedia.org/wiki/Data_compression

Compression Artifact

Lossy compression algorithms sometimes introduce visible or audible aberrations in the product. Visual artifacts are sometimes described as blurry or blocky regions of an image. Audio artifacts are sometimes described as sounding tinny, crashing, or echoing.

http://en.wikipedia.org/wiki/Compression_artifact

Cube2Dome

A program that stitches 5cam frame sets into fisheye projection frames.

In Ott Planetarium Productions this method is used less frequently than the Hemicam method.

http://local.wasp.uwa.edu.au/~pbourke/projection/cube2dome/

Display Circumference

In planetarium production, a calculation of the pixels around the perimeter of the dome.

This calculation is useful for determining appropriate source image resolutions. A source image with low resolution will look blurry or blocky on the dome, a source image with too much resolution will be computationally expensive to render.

Examples: Mediaglobe display circumference is about 3200px.

Frame Rate

In video, the number of times the image is updated in a given amount of time (usually seconds).

Frame rate is an important factor to consider when producing digital video. If the video is designed for DVD, the framerate should match the NTSC standard. If the video is designed for computer playback (eg: Mediaglobe Planetarium), the framerate should match the display standard. A framerate mismatch can introduce scan line aberrations in the product.

Examples: Ott Planetarium Productions: 30 FPS; NTSC Broadcast: 29.97 FPS.

Hemicam

A camera and hemispheric reflector combination developed for rendering fisheye projection frames directly from Blender in one render pass.

Our current Hemicam can be downloaded in "Files."

This method is used almost exclusively in Ott Planetarium productions.

NTSC

Refers to the standard analog television system in the United States, Canada, Mexico, Japan, and several other countries. The standard was named for the National Television Standards Committee, established in 1940.

The NTSC broadcast standard defined the analog television signal as a 525 line transmission with a frame rate of 30 FPS (1/2 of the U.S. electrical frequency of 60Hz), consisting of two interlaced fields per frame. With the advent of color television, an additional carrier signal was needed to transmit analog color data. For technical reasons this additional carrier required the framerate to be reduced to 29.97 FPS.

Ott Planetarium Productions use 30 FPS because it is much easier to calculate timing with an integer framerate. Unless a production is specifically designed for DVD, we do not use the NTSC standard.

http://en.wikipedia.org/wiki/Ntsc

PAL

Refers to the color encoding system used in broadcast analog television in many parts of the world. PAL is short for Phase Alternating Line.

The PAL system uses a framerate of 25 FPS (1/2 of the electrical supply frequency of 50Hz, where employed). PAL is the second European color television standard (after SECAM, which is still used in parts of Africa, Russia, and former Soviet states).

The default frame size and framerate in Blender conforms to the PAL standard.

Ott Planetarium Productions use a framerate of 30 FPS (not PAL). Unless a production is specifically designed for European broadcast television, we do not use the PAL standard.

Pixel (px)

A unit of measurement in digital media. Often used to express resolution depth and image dimensions (frame size). A pixel is one "dot" in a raster image.

Example: The Mediaglobe Planetarium projects 1024x1024 px.

Pixel Aspect Ratio

A term referring to the ratio of horizontal and vertical size of a pixel in a given display.

An NTSC pixel aspect of 1:0.9117 is used for DVD and broadcast media productions.

Ott Planetarium productions usually employ a pixel aspect of 1:1 (square pixels).

PNG

A lossless raster image format that supports RGB an alpha channel (RGBA) with up to 64 bits per channel.

Animation can be created by streaming a numbered sequence of PNG images. Ott Planetarium productions usually employ PNG as the dome master format.

Pronounced: "ping."

http://en.wikipedia.org/wiki/PNG

qBlender

A script used to submit render jobs to Waradmiral. qBlender offers allows users to submit jobs with relative asset paths intact, thus solving logistical problems for render jobs requiring external assets.

(Internal use only.)

RAID Array

RAID: Redundant Array of Independent Disks

Waradmiral's RAID array has a capacity of 5 TB this is separate from Waradmiral nodes' disk space, which is considerably less. The RAID is used for data storage and transfer.

See: Waradmiral, WRCRS.

Raster Image

A two dimensional array of pixels, also known as a bitmap.

The end product of a render is usually a raster image. A single production employs thousands of raster images as frames in an animation.

Raster images are difficult to enlarge without quality degradation.

Common Raster File Formats: PNG, TGA, JPEG, BMP, GIF.

Subversion (SVN)

In computing, Subversion is a version control system by CollabNet Inc. It allows users to keep track of changes made to any type of electronic data, typically source code, web pages or design documents.

Ott Planetarium uses SVN to manage large production projects, such as the Astro Otters and Astro Otters Jr. National Astronomy Program.

Vector Graphics

A method of describing images using mathematical expressions instead of pixel arrays. Vector graphics are easily scaled to many times their original size with no loss of detail.

Common Vector Graphic Formats: Flash, SVG, AI, CDR, and PDF. *(These vector formats support the inclusion of bitmaps, which can not be upscaled without some loss.)

http://en.wikipedia.org/wiki/Vector_graphics

WRCRS (Work Horse)

The Weber Render Cluster and Research Supercomputer.

The WRCRS consists of 32 rack mounted Xserve Quad Xeon servers and a 5 TB RAID Array. The WRCRS cluster contains 128 CPU cores, for a combined speed of 340 GHz.

Pronounced: "work horse."

See: RAID Array, Waradmiral.