Projection Mapping

Projection mapping is an advanced technique to place moving media onto non-standard screen shapes, which could be buildings, a vehicle or in fact any 3D shape.

Typically, a content creation house will generate media and a matching 3D model either from a 3D CAD package or by laser-scanning the physical object.

The media and 3D model is then transferred to a Delta Media Server, which is configured in Mesh Mode where the scene is maintained in full 3D and completed with camera viewpoints which match the physical projector positions relative to the real 3D object.

By configuring a virtual scene within Delta to match the physical scene, each projector “sees” the correct view of the object, placing media on the correct portion of the model and allowing multiple projectors to blend together to cover the whole 3D surface.

SEMI-AUTO 3D CALIBRATION
As part of the suite of alignment tools, 3D Auto-Cal is built into Delta Mesh Mode as one of the key alignment stages which helps to minimise the time required onsite.
Since the aim in Mesh Mode is to build a 3D virtual set which matches the real 3D scene, you could measure each projector position, angle and lens characteristics and type them in directly to Delta – this is a recognised technique and is successful if the measurements are reasonably accurate.

However, the time-pressure onsite and the reality of the onsite environment can make accuracy difficult to achieve, since the projectors may be physically unreachable and the lens zoom / offset hard to measure in situ.

Delta’s 3D Auto-Cal is a mechanism whereby the operator places at least 6 markers on the virtual 3D model within Delta, then moves each marker projected on the real 3D object to the corresponding 3D point. Once this is achieved, Delta calculates the position and lens characteristics which match the 6 points and configures that channel automatically. This is repeated for each projector and saves a lot of time compared to manually working out each projector position and of course the resultant view can still be adjusted if required.

Once the correct camera view from each projector is achieved, it is still possible that the geometric alignment is not perfect due to differences in the 3D virtual model compared to the real thing, and this is where Delta’s Mesh Editing is used.

MESH EDITING
The 3D model and media from the content creator typically consists of a OBJ format file which contains the 3D mesh and UV texture coordinates accompanied by a movie (TGA sequence preferred) or still imagery (any format).

Once imported to Delta in Mesh Mode, the 3D model is viewed from matching projector positions, but there may still be differences from the real 3D object to the virtual model.

Delta’s Mesh Editor allows the operator to view the 3D model from any viewpoint, select one or more vertices in the model and move them in X, Y or Z to better match the observed model. This alignment can be carried out for all projector channels (World coordinates) or done per channel to achieve the correct view from each projector. Once the alignment is complete, simply saving the normal Delta show saves all adjustments to separate companion files to the original OBJ file so that the original OBJ is left untouched – you can reset single or multiple points at any time, even after saving the file as the editing is completely non-destructive.

Other features in the editor are the ability to hide single or multiple faces in the model, apply clipping planes to the model to achieve easier selection, alter the movement size to match the model dimensions, and “bake” the complete adjusted model to a new OBJ file for round-trip editing with the content house.

REAL-TIME TRACKING
Using third-party camera based tracking systems, Delta can be configured to receive the real-time data-stream of multiple points in the scene which are placed onto 3D points of the physical object.

This data is then used to move the corresponding 3D object inside Delta in sympathy with the physical model, providing a tracked match between virtual & physical worlds.

The tracking data can also be extended to track projector positions so that both 3D object and projector can move within the scene and still provide matching content on the object.

Content placed on the object therefore stays on the object as it moves, providing creative possibilities to theatre productions or live events.

This technology also appears in museums, theme park rides and visitor attractions to entertain customers with unique and surprising audio visual experiences.

Projector Layout & Design

Delta has been designed by experts in display systems, who have been involved in every type of projected and fixed matrix type of display system ranging from large screen cinema, multi-channel digital planetariums to 6,000 seater theatres, flight simulators and full-scale building projection to mass audiences.

This in-house knowledge has been used to build the best display management tools available so that Delta can cope with any display surface, whether it is a regular screen or abstract shape.
Delta has the following display-related features:

  • Flat, curved, half-dome, fulldome & 3D modelled shape screen types
  • Underlap & Overlap creation
  • Cross-server “canvas” paradigm creates a single coherent multi-server display surface
  • Comprehensive warp & blend
  • Projection mapping Mesh Mode
  • Spherical or ellipsoid dome screen layout designer, fisheye media support
  • In-GUI visualisation of the flat, dome or 3D mesh screen
  • Composition Mode allowed complex LED processor packing of media & output channels
  • HDMI, DVI, DisplayPort, SDI output support, with 8, 10 & 12-bit video modes & media
  • Real-time movement of channels on the canvas to support flying LED screen automation
  • RGB & XYZ colour space support.

Dome Mode

Delta has a virtual 3D dome model internally with the ability to position & locate the screen and multiple projectors in 3D space (by XYZ, HPR) as well as configure each projector channel according to the lens zoom and offset.

This allows each channel to have the exact view of the dome surface as in the real system so that the start point for alignment is already very close. However, in real systems, the dome radius or shape is never exact, and the projector lens may not be known perfectly, so some warp is usually necessary to achieve a proper alignment.
Dome alignment can be done manually by a technician using Delta’s built in warp & blend controls, or automatically using any of a range of third-party camera based auto-alignment systems.

For media, Delta supports fulldome fisheye masters (for example 4K x 4K), playing directly onto the dome in real-time with no requirement for offline carving, and additionally supports a mix of flat, panoramic or channel mapped media which can be placed on-screen in the intuitive angular canvas units.

3D dome media and displays are also supported.

3D Stereo

3D Stereo projection provides the extra dimension to immerse viewers in the storyline and since the mass take-up of 3D technology, content creators have become ever more skilful at deploying the right amount of 3D to enhance the viewer’s perception.

Delta supports the following stereo modes:

  • Passive Stereo (inexpensive polarised glasses / one projector per eye + non depolarising screen)
  • Passive Stereo (inexpensive Infitec glasses / one projector per eye)
  • Active Stereo (active shutter glasses / single active 3D projector)
  • Anaglyph (inexpensive red/blue glasses, any projector)
  • Chequerboard Passive Stereo (typically used in 3D LED screen)

In addition, the following 3D-relevant features are provided:

  • 3D Content as separate left / right eye movies
  • 3D Content as single side-by-side or top-bottom movie
  • Create anaglyph stereo in real-time from non-anaglyph content
  • 3-pin DIN active stereo output (model dependent)
  • Multi-rack synchronisation supports multiple active or passive 3D projectors
  • 3D fulldomes are supported