Attenuation with Light Decay filter

- [Narrator] Arnold obeys physical laws,…but also gives us the freedom to art direct…the look of our lighting, using physical parameters,…just like a real cinematographer or photographer would.…Also, to a considerable extent we are…permitted to bend or break physical laws…to achieve our desired production goals.…In lighting, one of the primary concerns…is control over attenuation or light decay.…In physics, this is described…by the so called inverse square law.…

It states that a radiant energy source…will diminish in intensity, according…to the inverse square of the distance.…In Maya terms this is known as a Quadratic Decay.…In Arnold version five, point spot…area and mesh lights all use Quadratic Decay.…The decay rate setting that you may…be familiar with in the Maya light attributes is ignored.…Intensity curves do work correctly,…but the effect of the intensity curve…is combined with the Arnold decay.…

For physically accurate illumination…with omni directional light sources…then we need Quadratic Decay.…However, many lighting instruments…