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Since we're tracing through the scene collecting light, it might be important to specify how much light you need or want to collect. This is usually meant to separate the direct and indirect events mentioned above. But you may also specify how many bounces along this path you want to collect rather than let the renderer collect all of them. Collecting specific bounces is covered later.
To begin we'll look at the usual notation for Direct and then Indirect light collection.
Above we were defining events and their type. But we need a way to say how many of these we want. We could manually string together events in a particular order but that becomes a painful experience in copy and paste. It's better to let the renderer make the decision for you. We have two common ways to define how many of our defined events we want.
Asterisk
* means zero or more of these preceding events. Since it's zero or more, it will collect a direct lighting event and the ones that follow it (meaning indirect) til they reach a light source. It's the simplest way to capture light for the whole path. The following collects only diffuse reflection and all the events that match diffuse reflection until it strikes a light.
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lpe:C<RD>.*[<L.>O] |
Plus
+ means one or more events. This means after the initial event, begin collecting others. This means it will collect indirect lighting only as the first (direct) event is skipped. Below is only indirect diffuse reflection (the typical indirect light AOV)
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lpe:C<RD>.+[<L.>O] |
None
If none of the notations are used, it collects an event and then goes to the light, collecting only direct lighting. Below we omit the * and the +, only direct diffuse reflection is collected.
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lpe:C<RD>[<L.>O] |
The Beauty Render
Let's look at an expanded beauty LPE. And by "expanded" I mean with all the parts spelled out and not in shorthand (which we'll cover later).
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