Here is some "quick start" documentation on how to make your FxPlugs work in Final Cut Pro X:
Making FxPlugs work in Final Cut Pro X
In order to make FxPlugs work in Final Cut Pro X, you need to create a Final Cut Effect within Motion which rigs and/or publishes your FxPlug's parameters. The best place to learn how to do that is the Motion documentation. See chapter "Using Rigs" for complete details. Below is a brief description of the process.
Keep in mind that users of Final Cut Pro X are looking to solve specific tasks rather than to apply particular effects. In general, you should avoid publishing long lists of parameters that are likely to confuse users and make completing their tasks harder rather than easier. Advanced users who need more control will be able to either open your Final Cut Effect in Motion and edit it themselves, or create their own Final Cut Effects within Motion for their specific task. Less advanced users will be overwhelmed by filters that are too complex and won't generally need to control every parameter in a given filter.
Creating a Basic Final Cut Pro Effect
To create a basic Final Cut Pro Effect you can do the following:
1) Open Motion
2) Create a new Final Cut Pro Effect document from the Project Browser:
This should create a new Motion document with a drop zone named "Effect Source" in the timeline
3) Apply the "Glow" filter to the Effect Source Drop Zone. Note that anything you can do in a Motion document can be done in a Final Cut Effect, Generator, Transition, or Title. You can apply multiple effects, create shapes, supply text, and even use audio
4) Select the newly applied FxPlug and open Motion's Inspector to reveal its parameters
5) When you mouse-over the Radius parameter, you'll notice a popup-menu indicator appear to the right of the Radius slider. Click on it to reveal the parameter's option menu. Choose "Add To Rig" > "Create New Rig" > "Add To New Slider"
You'll notice a new "Rig" group created in the layer list, with a new layer named "Slider" which is now selected
Double click on the name "Slider" in the layer list and change the name to "Glowiness"
When this effect is applied in Final Cut, it will now show a single parameter named "Glowiness". Next, we'll connect it to 2 different parameter so the user can control them at the same time
6) Next, select the Glow filter again in the layer list to display its parameters in the Inspector
The "Radius" parameter should now have an icon of a joystick to the right
7) Click on the popup menu for the "Opacity" slider and choose "Add To Rig" > "Rig" > "Add To Glowiness"
8) Show the Glowiness slider in the Inspector by selecting it in the layer list. The slider should be displayed with 2 circles below it, one at the left end of the slider and one at the right end. Select the one on the left by clicking it
9) Set the "Effect Source.Glow.Opacity" slider to 0 and the "Effect Source.Glow.Radius" slider to 0. This sets the Opacity and Radius parameters to 0 when the rigged slider is set to 0
10) Select the circle under the right end of the Glowiness slider by clicking on it
11) Set the "Effect Source.Glow.Opacity" slider to its maximum value, and do the same for the "Effect Source.Glow.Radius" slider
Now when the user moves the Glowiness slider in Final Cut's inspector, both the Opacity and Radius parameters will increase
Publishing Parameters
Now, let's publish the "Threshold" parameter so the user can control it directly. Publishing a parameter is different from rigging. With rigging, you can tie one user-visible parameter to a host of parameters in your Final Cut Effect. With Publishing, a parameter is directly accessible to users.
1) In the layer list, select the Glow effect so its parameters will be displayed in the Inspector
2) In the Inspector, click on the "Threshold" parameter's popup menu and choose "Publish"
3) Finally, save the effect
When you attempt to save a Final Cut Effect, Transition, Generator, or Title, you're presented with some options. In addition to a name, you can assign the effect to a category, which is where it will show up in Final Cut's Effect Browser. You can optionally choose a Theme, as well.
4) Once you have a name and category, click the "Publish" button
Your effect should be immediately available in Final Cut. You do not need to quit Motion or quit and restart Final Cut to see it.