Any non-perpendicular projection requires a degree of warping in order to correct for perspective. This procedural guide covers flat plane screens – which includes curved screens, but not spherical surfaces – and uneven surfaces, but not polygonally-mesh-mapped ones. Once set up, the display configuration for the theatre can be saved and loaded separately, to be merged with any show.
Three Adjustments per Channel: Shape, Overlap Brightness, and Colour
The basic principle is that since the canvas as a whole is divided into areas covered by several channels, each channel will require its own correction by warping to maintain both aspect ratio and perspective. The channels will need to overlap for smoothest continuity, corrected for luminance by blending, and differences in characteristics between projectors may finally require correction for colour.
•The alignment task is about mapping a seamless, evenly-proportioned grid, across all channels, onto the physical canvas, without distortion, duplication or cropping, using the various warping tools.
•The blending task is about making the joins between channels invisible through luminance blending and colour correction.
In the example used here, projectors are in line, but other configurations are possible.
Physical Setup and Tools
We assume here that the theatre setup has provided you with enough information to know media size, physical canvas properties and degree of overlap between channels, and that best efforts have been made already in aligning projectors correctly. The procedures outlined here will apply every time readjustment is necessary, for example following regular maintenance.
Since one of your key tasks will be to ensure that the size and aspect ratio of every grid square is the same, some basic tools will be useful, including, for example, a laser line (to find true horizontal and vertical) and a tape measure.
Autoalignment, such as Scalable Display Manager™, is a practical though more expensive solution, but for more complex surfaces may be worthwhile (enable this in Config > Startup & File Load). Please note: AutoAlignment is a licensed option.
Sequence in DeltaGUI
•Know your canvas size, your overall media size, the approximate channel overlap, and how your channels are distributed.
•Use the information in the Defaults Wizard to distribute active channels, positions, and overlap for Delta, and to generate default background warps and blends.
•Turn on the pixel grid display, and adjust channel X and Y locations, and overlap to bring the defaults approximately into line with reality.
•Adjust each channel for proportion and linearity, and align each channel to the next, using surface, timeline and point distortion warp.
•Display test patterns or flat colour media in order to apply blends and adjust overlap luminance.
•Save the .xdl display configuration file to use for any show in this configuration.