ANSI-IES TM25:2020 pdf download.TECHNICAL MEMORANDUM:RAY FILE FORMAT FOR DESCRIPTION OF THE EMISSION PROPERTIES OF LIGHT SOURCES.
This document provides recommendations for a standard ray file format to describe the emission properties of light sources. The ray file format contains information necessary to interface between ray tracing or other optical design, simulation, analysis and metrology software used in lighting applications.
2.0 Normative References
2.1 ANSI/IES IS-1-20
Nomenclature and Definitions for Illuminating Engineering. New York: ES; 2020. Online: www.ies.org/standardsI definitions/. (Accessed 2019 Mar 22).
2.2 ISO 8601
Date and Time Format, Parts 1 and 2. Geneva: International Organization for Standardization, 2019.
2.3 IEEE 754-2008
IEEE Standard for Floating-PointArithmetic. New Jersey: Institute of Electrical and Electronics Engineers; 2008.
2.4 The Unicode Standard
The Unicode Standard. Mountain View, Calif.: The Unicode Consortium.
2.5 The International System of Units (SI)
The International System of Units (SI), 8th ed. Paris: International Bureau of Weights and Measures (BIPM); 2006.
2.6 ISO/IEC 8859-1 :1 998
Information Technology — 8-bit single-byte coded graphic character sets — Part 1: Latin alphabet No. 1. Geneva:
International Organization for Standardization, 1998.
3.0 Definitions and Nomenclature
3.1 ASCII
An encoding scheme for Latin characters, according to ISO/IEC 8859-1 (see Section 2). For the purpose of this standard, only the character 0 and characters from 32 up to and including 126, in decimal form, shall be used.
3.2 binary
An encoding of information into certain data types in files creating a sequence of items that can be used immediately as data by computer processors without further conversion; the sequence of binary items is, in general, not a sequence of encoded human-readable characters.
3.3 binary32
A certain binary floating-point encoding format defined in IEEE 754 (see Section 2), using four bytes of memory per
floating-point number. The binary32 format is commonly used by C and C++ compilers to implement the “float” data
type.
3.4 byte
A unit of digital information, consisting of 8 bits.
3.5 denormalized real
As defined in IEEE 754 (see Section 2): a number whose absolute value is nonzero but smaller than 1.18 x 10-38, and thus too small to be encoded within the IEEE 754 binary32 floating-point format at full mantissa resolution.
3.6 direction cosine
Ray directions within the scope of this Standard shall be given as unit vectors in a three-dimensional Cartesian coordinate system (a unit vector is normalized to have a 2-norm, or Euclidean length, of 1). Each coordinate value of a unit vector is mathematically equal to the cosine of the angle between the vector and the corresponding axis. Therefore, the ray direction coordinates are often called direction cosines.
3.7 fatal error
When any data in an IES TM-25 ray file shows a condition denoted “fatal error” within this Standard, then the ray file shall be considered invalid.ANSI-IES TM25 pdf download.