Chapter 1 – Introduction
Terminology
Truelight SDI User Guide
4
Truelight cube
When Truelight applies a transform to an input colour (three values), it can apply a 1D
LUT (one for each input channel) followed by a 3D LUT, both regularly sampled. This two-
step rendering process allows for accurate interpolation without needing excessive
sample points in the 3D LUT. The number of samples for both the 1D and 3D LUTs is
specified within the Truelight profile (see below) from which it was generated, though
some Truelight rendering systems (like the Truelight SDI unit) may impose their own
restrictions. You can omit either of the 1D or 3D LUTs.
This combination of LUTs is referred to as a
Truelight cube
. It is usually generated from a
Truelight profile when required and so there is generally no need for a corresponding file
format. However, third parties that want to make use of the Truelight rendering engine
can use the Truelight text file format specification to input the LUT values directly (as
described in the
Truelight Cube Format
document). Also, when a profile is selected for
loading onto Truelight hardware (like the Truelight SDI unit) it is communicated to and
stored on the unit as a cube.
Since the Truelight cube is more general than most other colour transform LUT formats
(the majority of which are just 3D LUTs) Truelight can reinterpret third-party LUT files
into Truelight cubes for direct use in the rendering engine.
Truelight profile
A Truelight profile is a collection of special instructions and, usually, empirical data which
gets ‘compiled’ into a Truelight cube at the time it is used.
A typical example of a Truelight profile is a description of how to emulate a film output
process and projection on a particular digital projector—raw measurements of the film
processes and the projector are included in the profile file together with other
parameters such as those relating to the viewing environment (like flare).
This file is widely used as means of communicating the viewing intention of certain
images from one FilmLight system to another. By sending the profile, rather than the
cube generated from it, the end viewer can easily replace the data relating to the
projector with a calibration of their own display system, thereby ensuring that the view
of the images is the same despite using a different display system.
Term
Description
