GSoC 2025: Ergonomic API for Vector Mesh Topology

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My name is Priyanshu Raj and I've been selected as GSoC 2025 student developer to work on Graphite. Throughout the summer I will be working on creating an API for editing vector mesh topology.

Synopsis

The project aims to design and implement an ergonomic and efficient API for accessing, manipulating, and performing operations on vector data such that implementing complex vector based algorithms or developing tools to perform vector manipulations is efficient and ergonomic. The second aspect of the project is to enhance performance and stability by transitioning from Bezier-rs to Kurbo algorithms and data structures to perform vector operations.

Benefits

• Significant improvements in performance and reliability.
• An ergonomic API will simplify the development of advance vector mesh topology editing tools.

Deliverables

• An ergonomic API to access, manipulate and do vector operations will make it intuitive for developer to implement complex algorithms and add functionality to tools.
• Implementation of efficient data structures and algorithms will lead to better performance hence it will improve the user experience.
• Use of Kurbo API in place of Bezier-rs will lead to more maintainable and robust code.

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Community Bonding Period

In this three week time period I worked on refactoring code to use Kurbo instead of Bezier-rs. This resulted in significant performance and accuracy improvements while also fixing a few bugs.

Nodes refactored to use Kurbo API:

• 'Offset Path' node (Replace Bezier-rs use in the 'Offset Path' node with a Kurbo algorithm #2596)
• 'Solidify Stroke' node (Refactor the Solidify Stroke node implementation to use the Kurbo API #2608)
• 'Position on Path' and 'Tangent on Path' nodes (Refactor the 'Position on Path' and 'Tangent on Path' nodes to use the Kurbo API #2611)
• 'Sample Points' node (Refactor the 'Sample Points' node to use Kurbo instead of Bezier-rs #2629)
• 'Scatter Points' node (Refactor the 'Scatter Points' node to use Kurbo instead of Bezier-rs #2634, Fix 'Scatter Points' node artifacts #2657)

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Week 1

• Explored different approaches and techniques to find the line between two connected segments for bevel algorithms, though I haven't found a good solution yet.
• Fixed a bug in the morph node implementation.
• Planned out some of the API to start with for the vector mesh and how I'd implement it considering the refactor.
• Refactored the 'Morph' and 'Bounding Box' nodes to use Kurbo instead of Bezier-rs.

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Week 2

• Started to work on prototyping a data structure to represent a vector mesh.
• Worked on refactoring the 'Centroid' node to use Kurbo.
• Started to work with the help of @4adex on refactoring methods for modifying vector data such that the function returns the index of the vector data in the row of VectorDataTable instances.

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Week 3

This week I started off by implementing new nodes 'Path Length', 'Count' and 'Split Path' and then worked on the prototype for testing ideas and design for a fresh vector mesh representation that is easy to understand and work with for both the user and developers.

Implemented a basic vector path edit tool and structure for representing vector mesh in the prototype and implemented a few basic APIs for query and manipulation of the data.

While working on the prototype, I spent most of my time thinking about the structure for the vector mesh such that the data is represented as a table and is also efficient to access and manipulate for implementing APIs. Initially @Keavon suggested storing it as list of commands which describes the path like Kurbo does. Though this approach gives a simple way to represent the data I wasn't sure if implementing APIs with this would be efficient and also make it easier for the users to work with. I proposed to represent the vector mesh data as a list of points, segments, and attributes very similar to how it is represented currently. Then, while discussing my proposed idea, @Keavon suggested an even better approach which is to represent the segments components as columns in a table, just like attributes which feels like the best approach which works for the users and developers.

@4adex and I also diccused a new approach for filling the regions which is dynamic and created by the intersections of path segments in a mesh. The idea he proposed is to store the fill of the regions as a list of fill which is left or right of the subsegments that are part of that region and then compute the fills of each region by calculating the fill which is present in most of the subsegments that construct that region.

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Week 4:

• Fixed a bug in the 'Morph' node implementation.
• Worked on Path nodes should be able to edit multiple vector table rows #1822 .
• This week I've been mostly working on prototyping the mesh structure and also spent some time on experimenting with other approaches for styling dynamic regions and strokes which is
  • Subdivide the curves of an nth-degree bezier curve into n number of subcurves.
  • Represent a region by referencing subsegments and the direction and style of the region to the subsegments that construct that region at any instance.
  • This is slightly different from the older approaches that were diccussed in the mesh vector discord channel. I got this idea while testing and documenting the approach we have previously discussed.

In the above drawing I got stuck when thinking about regions which are constructed by more than two curves and started to find a different approach. Next is to figure out how we can store and represent stroke styles applied to the segments of the paths in a vector mesh.

• I also spent some time reading the 'Pen' and 'Path' tools code while writing the prototype to find a cleaner way to implement the tools. I've got some idea which I will try to prototype in the same prototype project I am working on for vector meshes.

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Week 5

• This week I worked on implementing the 'Pen' and 'Path' tools in the prototype and some APIs to manipulate segments and points in the vector mesh structure.
• I also spent some time thinking of a simpler algorithm to traverse all the regions in the vector mesh in which there are no overlaps between any two segments.

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Week 6

• This week I implemented function to convert simple verter mesh into planar vector mesh and a function to get all the regions in the prototype.
  • Convert a vector mesh into a vector mesh where no two segments intersect each other (Planar Graph)
  • Traverse and construct all the regions in the vector mesh.
  • Apply styles to the dynamic regions and then calculate the styles to render these regions.
  • Apply styles to the strokes and also render them.

Dynamic.vector.mesh.traversing.mp4

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Week 7

• Implemented applying and rendering of fills to the regions in the vector mesh in the prototype.
• Refactored 'Offset Path' node. Refactor the 'Offset Path' node to use Kurbo entirely #2946

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Week 8

• I was unable to make progress this week as I was occupied with moving to a new place and was also feeling a bit unwell. I am settled now and plan to resume work next week.

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Week 9

• Refactored a few vector nodes and unit tests to use Kurbo (Refactor the 'Round Corners' and 'Auto-Tangents' nodes and vector node unit tests to use Kurbo #2964).
• Refactor the 'Centroid' node to use Kurbo (Refactor the 'Centroid' node to use Kurbo #2977).
• Worked on vector mesh prototype for rendering dynamic strokes.

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Week 10

• Refactored the 'Centroid' node. Refactor the 'Centroid' node to use Kurbo #2977
• Moved the 'bezier-rs::Subpath' struct into node-graphs gcore crate and refactored it to use Kurbo API . Refactor the Centroid node and Subpath struct and methods to use Kurbo, eliminating all remaining usages of Bezier-rs #3036

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Week 11

• Refactoring vector mesh protoype project.
• Wrote an algorithm to idetifying strokes in dynamic vector mesh.
• Fixed a few edge cases in the vector mesh prototype project.

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Week 12

• Fixed a Path tool regression Fix a Path tool regression where selection depends on box winding direction #3062.
• Improved the algorithm to uniquely identify regions in the vector mesh prototype project.
• Fixed the BezPath insideness checking function.