Table E.1 is taken from ISO/IEC 9592-1:1997, Annex H.

Table E.1 — Variable definition and their sources

Source Legend:

[1] Light source representation

[2] Calculated

[3] Explicit or derived from object geometry

[4] Source of intrinsic colour (ISO/IEC 9592-1:1997 table 18, 4.5.8.5)

[5] Reflectance properties

[6] Calculated per formulae given in E.2.

The following equations are taken from ISO/IEC 9592-1:1997, Annex H.

The result of the reflectance formulae evaluated at the point on a primitive is a single colour that is the sum of the individual components C _a +C _d +C _s of all the currently active light sources, as follows.

For ambient light sources

For directional light sources

For positional light sources

For spot light sources: (Contributions from one spot light sources will be zero if O _p is outside the cone of influence of the light source.)

Light attenuation may be calculated as follows:

where |O _p -L _p | is the distance between the object and the light source. The reflection vector may be calculated as follows:

In the calculation of C _d and C _s , a dot product resulting in a negative number is replaced by 0. In the calculation of

For interior shading method 3 (DATA) the quantities

For interior shading method 4 (DATA and DOT) the quantities

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