Writing Efficient LPEs

Here are a few different ways to write LPEs such that MoonRay processes them efficiently.

Avoid OR-lists [ ]

MoonRay converts all of the LPE expressions into one large, tree-like structure. OR-lists cause this tree to branch, which greatly increases the amount of time it takes to process the tree.

Use the exclusion symbol ^

One good way to decrease the number of possibilities MoonRay has to process is to use the exclusion symbol ^ instead of a long OR-list.

For example, suppose we wanted to exclude the diffuse hair lobe, and we were writing:

["diffuse" "diffuse transmission"]

It is much more efficient to write it like this:

<.D[^"diffuse hair"]>

Use groups <> where possible

MoonRay is optimized to look for groups – anything that is not in a group will implicitly become a group in MoonRay. This is particularly a problem if you have an OR-list outside of a group.

For instance, the expression I used earlier:

["diffuse" "diffuse transmission"]

Will internally become the equivalent:

[<.."diffuse"> <.."diffuse transmission">]

You will note that this adds a lot of wildcards (increasing complexity!). It would be better to write it like so:

<..["diffuse" "diffuse transmission"]>

as it will stay pretty much the same when we process it internally.