Add usage guide and screenshot to README

README.md

@@ -2,9 +2,50 @@
 
 A [ResoniteModLoader](https://github.com/resonite-modding-group/ResoniteModLoader) mod for [Resonite](https://resonite.com/) that adds [easing function](https://easings.net/) presets to [ValueGradientDriver](https://wiki.resonite.com/Component:ValueGradientDriver) components.
 
-**Depends on [CustomUILib](https://github.com/art0007i/CustomUILib) to add the inspector UI!**
+*Depends on [CustomUILib](https://github.com/art0007i/CustomUILib) to add the inspector UI!*
+
+![Screenshot](https://github.com/djsime1/GradientDriverEasing/assets/8518150/c1977850-5ec8-400d-b917-1049964dcf55)
 
 ## Installation
 1. Install [ResoniteModLoader](https://github.com/resonite-modding-group/ResoniteModLoader).
 2. Place [CustomUILib.dll](https://github.com/djsime1/GradientDriverEasing/releases/latest/download/CustomUILib.dll) and [GradientDriverEasing.dll](https://github.com/djsime1/GradientDriverEasing/releases/latest/download/GradientDriverEasing.dll) into your `rml_mods` folder. This folder should be at `C:\Program Files (x86)\Steam\steamapps\common\Resonite\rml_mods` for a default install. You can create it if it's missing, or if you launch the game once with ResoniteModLoader installed it will create this folder for you.
-3. Start the game and browse to or create a ValueGradeintDriver component using the Inspector. Two new sections should appear on the component.
+3. Start the game and browse to or create a ValueGradeintDriver component using the Inspector. Two new sections should appear on the component.
+4. Consult the guide below to learn how the mod works.
+
+## Usage guide
+
+The additional UI is split into two sections: Easing utilities and Easing functions.
+
+### Easing utilities
+
+This section contains general settings and utilities. The first row controls the easing function endpoints.
+
+- `Min position`: Defines the minimum interpolation position for easing functions.
+- `Max position`: Defines the maximum interpolation position for easing functions.
+
+If there are 2 or more points in the Points list, these values will be automatically set to the minimum and maximum positions of the list. Otherwise, they default to 0 and 1 respectively.
+
+- <kbd>01</kbd>: Sets the min and max fields to 0 and 1 respectively.
+- <kbd>Auto</kbd>: Sets the min and max fields to the minimum and maximum positions in the Points list.
+- <kbd>Swap</kbd>: Swaps the minimum and maximum fields values.
+
+The second row contains buttons to manipulate the Points list.
+
+- <kbd>Sort position</kbd>: Sorts all Points in ascending order by their Position.
+- <kbd>-Position</kbd>: Inverts the Position of every Point (MaxPosition - Position)
+- <kbd>Subdivide</kbd>: For each pair of adjacent Points, adds a new Point between the two with values half-interpolated. Good for making easing curves more detailed.
+
+### Easing functions
+
+- `Target field`: Determines whether the easing function buttons apply to the Points Positions or Values.
+- - <kbd>Position</kbd>: Applies easing functions to the Position of each point according to its order in the list, with the `Min position` and `Max position` fields determining the lowest and highest values.
+- - <kbd>Value</kbd>: Applies easing functions to the Value of each point according to its Position, using the first and last list items as the curve start and end. **This will overwrite all the values inbetween!**
+
+The rest of the buttons will apply the corresponding [easing function](https://easings.net/) to all the Points Positions or Values, depending on your selection above.
+
+## Additional notes
+
+- Back, Elastic, Bounce, and Spring easing presets are only available when `Target field` is set to <kbd>Value</kbd>.
+- Back, Elastic, and Spring easing presets are clamped to the largest and smallest value in the Points list. Calculating interpolations beyond these values may be implemented in a future update.
+- When animating the ValueGradientDriver, you probably want to use [ConstantLerpValue](https://wiki.resonite.com/Component:ConstantLerpValue) instead of [SmoothValue](https://wiki.resonite.com/Component:SmoothValue); Otherwise the target value will be double-smoothed.
+- Thank you [cjddmut](https://github.com/cjddmut) for the [EasingFunctions.cs](https://gist.github.com/cjddmut/d789b9eb78216998e95c) code!