NAME

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

SYNOPSIS

C:

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>.  total_angle is the angle (in radians), measured from the light direction, in which the light intensity is non-zero.  For any point p, a line can be drawn from p to the light position.  If the angle this line makes with the light direction vector is between zero and (total_angle - delta_angle) the multiplicative factor is one and zero for angles greater that total_angle.  For values between (total_angle - delta_angle) and total_angle the multiplicative factor is a ramp from 1 to 0. 

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). 

SEE ALSO

DoLightSpreadExp(3D), DoLightAttenuation(3D)

September 29, 2021