bevy_pen_tool

A Bevy Engine plugin for making 2D paths, smooth animations, meshes and roads with Bezier curves.

Controls

Icon	Keys	Description
	Left Control + Mousescroll up	Scale UI and curves up
	Left Control + Mousescroll down	Scale UI and curves down
	Left Shift + Click	Spawn curve
	Left Crtl + Drag	Select curves
	Left Control + G	Group selected curves
	Left Shift + Left Control + Drag	Latch a curve to another curve by dragging a free anchor close to another free anchor
	Space + Drag	Unlatch anchors that were latched together.
	H	Hide anchors and control points
	Left Control + S	Save set of existing individual curves (does not currently preserve groups or latches)
	Left Control + L	Load set of saved curves (does not currently preserve groups or latches)
	Left Control + Left Shift + H	Hide the control points
	Left Shift + T	Compute look-up table (linearizes animations)
	None	Toggle sound
	Select curves or group + Delete	Delete curves or group
	None	Spawn road on curve group
	None	Spawn mesh inside curve group
	None	Spawn animated helicopter on curve group

Setup

Clone the repo, copy and paste the crate called "bevy_pen_tool_plugin" from the "crates" folder in the repo to the directory for your project, and add "bevy_pen_tool_plugin" as a local dependency in Cargo.toml. Refer to main.rs and Cargo.toml for futher details.

How to

A typical sequence of actions using the plugin would be as follows:

1. Spawn curves
2. Latch them together
3. Group the latched curves (cannot be ungrouped)
4. Move anchors and control points to desired position
5. Compute the look-up table
6. Save

A user can save and load the data structure for a group of Bezier curves -- called Group in the code -- in JSON format. The default directory for saving groups is "./saved/groups/", and the file extension is a custom one: ".group". Meshes can be saved in well-known ".obj" format, and their default save directory is "./saved/meshes". The one save button prompts a file dialog window for each data structure that can be saved in the current session.

There are two important parameters to tweak and they are both located in a Resource called "Globals"

1. group_lut_num_points: the number of elements in the generated look-up table (more yields smoother animations/meshes)
2. road_width: the width of the road meshes. Refer to main.rs to see how to modify these parameters.

When the control points, shown as arrow tips, are hidden, the plugin places them almost exactly on top of the anchors. In this mode of operation, one can draw an arbitrary polygon and generate the corresponding mesh.

Notes

bevy_pen_tool, in its current form,

• attemps to follow Bevy's latest release
• does not work with a Perspective Camera (only Orthographic)
• cannot save multiple groups at once, only a single one
• deletes everything on the canvas before loading a group of Bezier curves

TODO

• ability to move whole group
• select and delete mesh
• saving multiple groups
• ruler tool
• no guarantees, but maybe a 3D version