Light originates from a single point, and spreads outward in a cone.
Representation of https://threejs.org/docs/index.html#api/lights/SpotLight
Maximum angle of light dispersion from its direction whose upper bound is Math.PI/2.
The amount the light dims along the distance of the light In "physically correct" mode, decay = 2 leads to physically realistic light falloff.
If non-zero, light will attenuate linearly from maximum intensity at light position down to zero at distance.
In "physically correct" mode, the product of color * intensity is interpreted as luminous intensity measured in candela.
Percent of the spotlight cone that is attenuated due to penumbra. Takes values between zero and 100. Default is zero.
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