Funnily enough, not long after I posted my riveting summary of the Wom Archlight, a friend of mine using the light in production ran across an oddity and asked me about it. As it turns out it’s easy to fix, so I thought I’d post about it here. When using the Wom light shader attached to an area light he noticed that it didn’t behave as you’d expect. I give you exhibit 49f:
I’ve set the light to be visible in order to show the ‘problem’. The light is shining out of both sides of the rectangular area light! This is not the normal behaviour of a flat area light such as the rectangular and disc shapes. Generally you only want lighting coming out of the ‘front’ side that is represented with a little line, so you can light specific areas of a large object or perhaps just one of many objects and not those behind the light. Luckily this is as easy to fix as checking a checkbox. Because that’s what you do.
Ahh, good old ‘Cosine Distribution’! What? There’s quite a good technical explanation in the PDF manual supplied with the shader, but basically it tells the light to drop off it’s intensity as you reach perpendicular to the light’s surface. In a physically based way of course. The related attribute, ‘Cosine Exponent’ affects how quickly this falloff occurs:
So there you go! Quite useful for more precisely directing your light, a bit like an area spotlight but.. not. I imagine the Cosine Distribution attribute is off by default so that you can use spherical area lights with a light profile attached, which I know a lot of people in archvis use. The more adventurous among you could quite easily modify the AE Template script for this shader to enable it by default if you wished. I haven’t decided yet!
Peace out, light distributors!