DoLightSpreadAngles(3D) — Kubota Pacfic Computer Inc. (\*(Dd)

NAME

DoLightSpreadAngles − Create a light attribute object defining the width of the light beam of spotlights

SYNOPSIS

DtObject DoLightSpreadAngles(total_angle, delta_angle)
DtReal total_angle;
DtReal delta_angle;

FORTRAN:

INTEGER∗4 DOLTSA(TANGLE, DANGLE)
REAL∗8 TANGLE
REAL∗8 DANGLE

DESCRIPTION

DoLightSpreadAngles creates a light studio attribute object that defines a multiplicative factor modifying the light intensity as a function of the angle from the light direction. The DoLightSpreadAngles attribute defines the light cone for lights of type DcLightSpot <DCLTSP> or DcLightSpotAttn <DCLTSA>.

The two angles total_angle and delta_angle are measured away from the light direction.

DoLightSpreadAngles actually defines two cones of light. Anywhere within the center cone (total_angle minus delta_angle), the factor takes on the full intensity value (1.0). Anywhere outside the outer cone defined by total_angle, the factor is set to zero. Between the two cones, the value of the factor falls off gradually from 1.0 to 0.0.

The angles total_angle and delta_angle are, by default, expressed in radians. You can change the units to degrees by using DsSetAngleUnits <DSSAU> to set DcAngleDegrees <DCAD>.

ERRORS

DoLightSpreadAngles will fail if delta_angle is greater than total_angle or less then zero, or if total_angle is less than zero.

[WARNING - value out of range]

DEFAULTS

The default value for DoLightSpreadAngles is (pi/4, 0).

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