mapping: plug-in or not?

I'm contemplating writing a new mapping formula. I could write this as a transformation in a uxf file, or use Plug-In Transformation from Standard.ulb and write a UserTransformation to go in my ulb file.

So far, I don't see any advantages to doing it one way or the other. Comments?

In my experience the difference between a (mapping tab) transform and a plug-in transform (on the Outside tab if that is where your transform could potentially be used) is quite significant. The former transforms the whole image plane. The latter works on the trap shape and on individual iterations.

Being a bit of an orbit traps sort of fractalist I happen to prefer the latter as I like to manipulate traps and shapes. The plug-in style also has the advantage of allowing more than one transform to affect the trap shape if you use Transform Merge. Of course, your mileage may vary if you don't use the trappy style much but I expect the results between the two methods would differ somewhat there too.

Simple illustrative example in the image below:

1. is the basic point trap shape, no transforms
2. is the result of applying the Ripple transform on the mapping tab - ripple centred on whole image
3. is the result of using a plug-in Ripple transform (same param settings as 2) on the trap shape
4. is where two plug-in transforms are at work on the trap shape: Ripple and Wheel.

Plug-in transformations (like formulas and coloring algorithms) are more modular and flexible. For example, if you add the standard Plug-In Transformation and for the transformation choose from dmj5.ulb "Distort (fBm and more)", you can select different plug-ins for various aspects of the transform. For example, if you wanted the texture to be based on Voroni instead of fBm, change the "Distortion Texture" to "Voronoi Texture" in mt.ulb. The fBm and Voronoi textures (along with lots of others) were originally written for the orbit traps plug-in coloring, but can be used here to control distortion where it will have a somewhat different effect.

Also, if you write your new mapping as a plug-in, you (or anyone else) can select that mapping in a plug-in orbit traps coloring as the "Trap Position", which can generate interesting effects.

The downside to writing a new mapping as a plug-in is that other users not accustomed to using plug-in transformations won't find your mapping by browsing the .uxf files. They need to use Plug-In Tranformation and select the transformation from your .ulb file.

Good points from Velvet-Glove and rsidwell. I agree, thank you.

The standard Plug-In Transformation takes a UserTransform plug-in, and UserTransforms are usable in many places.

As the mapping transform takes #pixel as the argument, it may give interesting (and possibly unpredictable) results in a situation where it's given pz instead of #pixel.