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8.14.3.8 IfcLightSourceSpot

8.14.3.8.1 Semantic definition

NOTE Definition according to ISO/IEC 14772-1:1997: The Spot light node defines a light source that emits light from a specific point along a specific direction vector and constrained within a solid angle. Spot lights may illuminate geometry nodes that respond to light sources and intersect the solid angle defined by the Spot light. Spot light nodes are specified in the local coordinate system and are affected by ancestors' transformations. Figure 8.14.3.8.A shows the definition of spot light. spot light
Figure 8.14.3.8.A — Light source spot

8.14.3.8.2 Entity inheritance

8.14.3.8.3 Attributes

# Attribute Type Description
IfcRepresentationItem (2)
IfcLightSource (4)
IfcLightSourcePositional (5)
Click to show 11 hidden inherited attributes
IfcLightSourceSpot (4)
10 Orientation IfcDirection

Definition from ISO/CD 10303-46:1992: This is the direction of the axis of the cone of the light source specified in the coordinate space of the representation being projected.. Definition from VRML97 - ISO/IEC 14772-1:1997: The direction field specifies the direction vector of the light's central axis defined in the local coordinate system.

11 ConcentrationExponent OPTIONAL IfcReal

Definition from ISO/CD 10303-46:1992: This real is the exponent on the cosine of the angle between the line that starts at the position of the spot light source and is in the direction of the orientation of the spot light source and a line that starts at the position of the spot light source and goes through a point on the surface being shaded.

12 SpreadAngle IfcPositivePlaneAngleMeasure

Definition from ISO/CD 10303-46:1992: This planar angle measure is the angle between the line that starts at the position of the spot light source and is in the direction of the spot light source and any line on the boundary of the cone of influence. Definition from VRML97 - ISO/IEC 14772-1:1997: The cutOffAngle (name of spread angle in VRML) field specifies the outer bound of the solid angle. The light source does not emit light outside of this solid angle.

13 BeamWidthAngle IfcPositivePlaneAngleMeasure

Definition from VRML97 - ISO/IEC 14772-1:1997: The beamWidth field specifies an inner solid angle in which the light source emits light at uniform full intensity. The light source's emission intensity drops off from the inner solid angle (beamWidthAngle) to the outer solid angle (spreadAngle).

Table 8.14.3.8.B

8.14.3.8.4 Formal representation

ENTITY IfcLightSourceSpot
SUBTYPE OF (IfcLightSourcePositional);
Orientation : IfcDirection;
ConcentrationExponent : OPTIONAL IfcReal;
SpreadAngle : IfcPositivePlaneAngleMeasure;
BeamWidthAngle : IfcPositivePlaneAngleMeasure;
END_ENTITY;

8.14.3.8.5 References

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3 contributor(s):
Last change: Improve definition split (#876) * bring back headers headers were previously removed by mistake, now bringing them back * add new lines and rename the tag add the word 'short' in it * unify newlines make exactly one newline before and two after the tag * resolving typos Because bringing back headers required to go back in time to previous version, I'm now re-resolving the issues: #861, #860, #856 by ArturTomczak on 7/16/2024, 2:07:28 PM

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