# Fulldome, domemaster and 360° video explained Choose a format for an immersive dome: compare domemaster, equirectangular and flat video, understand mapping and resolution, and prepare reliable playback. Canonical: https://docs.theusualnext.com/en/learn/fulldome-360/ Updated: 2026-10-22 Publisher: the usual neXt **Fulldome** describes an experience projected across a dome. **Domemaster** and **equirectangular** describe ways to store image directions in a rectangular file. A dome can show either when the playback system maps the source correctly. Ordinary flat video has a different geometry and needs an appropriate screen or presentation mode. Understanding the source format prevents stretched images, wrong horizons and misplaced content. This guide explains the concepts and their use in TholusOS; see [media playback](/en/tholusos/media-server/playback/) for day-to-day operation. ## Compare the three common source formats A full-sphere equirectangular image commonly uses a 2:1 frame. A conventional 180° domemaster uses a circular fisheye image in a square frame. Flat video represents a rectangular view with its original aspect ratio. Dimensions are useful clues, but they do not prove how a file was authored. | Format | Typical image layout | Meaning | Example frame size | | --- | --- | --- | --- | | Equirectangular 360° | Longitude horizontally, latitude vertically | A full sphere around a viewpoint | 4096 × 2048 | | 180° domemaster | Circular image in a square frame | A hemisphere, with angular distance mapped radially | 2048 × 2048 | | Standard flat video | Rectangular composition | A conventional screen image | 1920 × 1080 | These are illustrative dimensions, not guaranteed playback limits or required export presets. Derivative documents equirectangular, fisheye and cubemap conversions, including the usual 2:1 and 1:1 output shapes. [Derivative, Projection TOP](https://derivative.ca/UserGuide/Projection_TOP). A square interview clip is still flat video. A 2:1 cinematic crop is still flat video. Conversely, a panoramic image can be cropped or packed in an unusual frame. Obtain the creator's projection specification before selecting a format solely from its dimensions. ## Understand a domemaster image A conventional equidistant 180° domemaster maps the zenith to the centre of a circle and the horizon to its rim. Angular distance from the zenith increases with radial distance from the centre. The frame corners lie outside the circular image and do not contain the hemisphere's picture. In this convention, the simple radial relationship is: ```text normalised radius = angle from the zenith / 90° ``` The centre has radius 0, a direction 45° from the zenith has radius 0.5, and the horizon has radius 1. This is a mapping convention, not a statement about a physical fisheye lens. The Blender manual distinguishes equidistant from equisolid fisheye models and identifies equidistant projection as suitable for fulldome output. [Blender, panoramic camera models](https://docs.blender.org/manual/en/3.2/render/cycles/object_settings/cameras.html). Confirm the **field of view and orientation** with the supplier. A fisheye source with a different aperture cannot be treated as a conventional 180° domemaster without considering that difference. Also identify which direction around the rim corresponds to the front of the audience. An image that looks distorted on a flat monitor may be correct when mapped to a dome. Judge proportions using the intended mapping and an orientation grid before editing the source to make its flat preview look natural. ## Understand an equirectangular image A complete equirectangular panorama maps 360° of longitude across its width and 180° of latitude across its height. The middle horizontal line is the equator; the top and bottom edges represent the poles. The left and right edges meet at the panorama's seam. This layout contains directions both above and below the horizon. A hemispherical dome shows the directions covered by its projection surface and chosen orientation. Converting the panorama to a domemaster is a directional remapping; merely cropping the rectangle or stretching it into a square does not perform that conversion. Watch for three source defects: - **A visible wrap seam:** the left and right edges do not join consistently. - **Pole artefacts:** objects or text near the top and bottom are distorted by the spherical mapping. - **An incorrect horizon:** the panorama is tilted or was authored with a different reference direction. Use a labelled directional test image to separate a source-orientation problem from a projector-calibration problem. If every source is misplaced in the same way, inspect the venue reference. If only one source is wrong, inspect its format and orientation first. ## Separate content mapping from projector calibration Content mapping interprets the source image as directions or a screen. Projector calibration maps those directions or screen coordinates onto the real projection surface. Keeping these stages distinct allows the same correctly described content to be used across different calibrated installations. A useful sequence is: ```text source file and projection format → orientation and presentation → calibrated surface mapping → projector warp and blend → physical projection surface ``` The content format describes what an image means. Warp maps describe how the installation displays it. A prewarped file exported for one projector arrangement may already contain installation-specific deformation. Applying another incompatible warp can distort it again. Before accepting a delivery, ask whether it is a reusable source master or a prewarped output for a particular venue. Record dimensions, projection, aperture, front direction, frame rate, audio layout and any embedded black borders. These details are more useful than a filename containing only “4K dome”. ## Select and check the format in TholusOS TholusOS distinguishes **Standard**, **Equirectangular** and **Fisheye / Domemaster** content. The content browser provides a format-correction action with Auto and explicit format choices. Use an explicit choice when the source specification is known and the existing interpretation is wrong. 1. Import the content and inspect its image, dimensions and supplier specification. 2. Open the video's format correction using the viewfinder action on its content card. 3. Select the source format that describes the file. Read dimensions from the file where needed. 4. Save the correction and prepare the content for playback. 5. Verify the horizon, front direction and proportions in preview and on the calibrated installation. Changing format metadata changes how the image is interpreted. It does not reconstruct directions that were never captured or turn a conventional flat scene into a complete spherical environment. For flat video, use the standard-video presentation workflow. Preserve the source's proportions and choose framing suited to the audience instead of forcing its edges around the full dome. Continue with [playback](/en/tholusos/media-server/playback/) for the operating steps. ## Assess useful resolution and readability Useful detail depends on angular coverage, pixel density on the surface, optical focus and the audience position. The resolution of the source file is only one part of the chain. A high-resolution file does not guarantee equally high detail everywhere on a curved display. For an ideal full-sphere 4096-pixel-wide equirectangular source, the horizontal sampling is approximately: ```text 4096 / 360 ≈ 11.4 source pixels per degree ``` A 90° horizontal view uses roughly 1024 source pixels before further resampling. This arithmetic describes source sampling at the chosen angular span; it does not predict final projector sharpness. The panorama's polar sampling, warping, overlap and physical screen introduce additional differences. Design text and diagrams for the installed surface. Test labels from the least favourable audience position, use strong contrast and allow enough viewing time. Keep detailed instructions on an appropriate secondary surface when the dome cannot present them legibly. For a final content check, include the full programme: bright and dark sections, motion, cuts, titles and audio. Preview confirms framing; actual projection establishes readability and visual quality for the venue. Use the [calibration guide](/en/tholusos/projection/calibration/) when defects affect all content, and the [black-level guide](/en/tholusos/projection/black-level/) when dark scenes expose the seams.