Per-Vertex Control Of Bezier Curve Bevel Size In Blender
Understanding Bezier Curves and Bevel Objects in Blender
A Bezier curve is a mathematically defined curve used in computer graphics and related fields. In Blender, Bezier curves consist of a series of vertices connected by edges that can be manipulated to create smooth curves and organic shapes.
Bezier curves are created in Blender by adding a Curve object and switching to Edit Mode. New vertices can be added along the curve by subdividing edges or directly inserting new vertex points. The smoothness and curvature of a Bezier curve is controlled by manipulating the handles attached to each vertex.
Once a Bezier curve object has been defined, a Bevel object can be added to give the curve extra depth and geometry. Bevel objects take the underlying curve and extrude new geometry along the curve’s edges based on the bevel object and its settings. This transforms a flat curve into a 3D-printable mesh object with volume.
Key settings for controlling a Bevel object’s geometry include the Offset to adjust inward or outward extrusion distance, Segments to increase edge resolution, and Profile to determine the curve’s cross-sectional shape. Additional caps with inside profile faces can be added for closed curves.
The Limitations of Default Bezier Curve Bevel Behavior
The bevel tools in Blender provide a fast way to create detailed curved geometry from a Bezier curve. However, the default bevel workflow lacks control over setting bevel dimensions per vertex point along the curve.
By default, the bevel effect size is only controlled globally via the Bevel Object settings. This means there is no way to localize the bevel size for a specific vertex or set of vertices without additional workarounds.
The lack of per-vertex size adjustments limits creativity for certain use cases. For example, creating a curved 3D pipe with fittings and gaskets that need specific sizing adjustments along the length of the pipe is not possible using Blender’s default tool set.
Using Vertex Groups to Control Bevel Size
To gain more control over the bevel effect, vertex groups can be used along with a Group Bevel controller node in the shader editor. Vertex groups provide a way to assign vertices on a model to categorized groupings.
With the object in Edit Mode, vertices can be selected and assigned to new or existing vertex groups in the Object Data Properties panel. Multiple groups with different vertices can be defined.
The Group Bevel node is then configured to map vertex groups to a Bevel Factor input. This factor scales the bevel extrusion amount for vertices in that group. A smooth transition between differently sized areas can be achieved using weighted vertex assignments.
In practice, this allows sharp transitions or gradients in bevel size by assigning vertices in certain regions to smaller or larger groups. Useful for changing pipe diameters, tapering effects, or markup transitions.
Advanced Size Control with Drivers and Scripting
For more advanced effects, bevel dimensions can be controlled dynamically using drivers or scripting to modify properties.
Drivers establish relationships between properties, such as the bevel factor, and other changing values like an empty’s transform or text input. Python expressions define how the values relate.
In this way, sliding an empty or changing a number field can scale parts of a bevel on the fly for animation and interactions. Custom scripts and add-ons take this further for specialized modeling and automated tasks.
Scripts allow programmatic access to adjust the bevel per vertex from an interface or tool. Complex generative models, user-facing controls, and logic systems can create intricate parametric geometry unmappable by hand.
Creative Examples and Use Cases
Per-vertex bevel control opens up options for more creative and customizable Bezier curves.
Stylized 3D Text: By manually editing vertex group assignments, artists can hand-craft pieces with sharp transitions in bevel size and flair for logos and text effects in motion graphics.
Customizable Cables: Scripts may generate cables, wires, and tubes with parametric diameters, connections, and gasket shapes tailored to user specifications for product designs.
The techniques also suit advanced concept pieces across transportation, product, architecture to integrate specific technical constraints into a model early on.
Conclusion
Controlling the bevel dimensions of a Bezier curve on a per-vertex basis requires utilizing vertex groups and Group Bevel nodes to remap parts of the geometry. For advanced uses, both drivers and scripting suit interacting with parameters.
Together, these tools help overcome limitations in Blender’s default bevel implementation for better precision in shaping curves. The output unlocks more creative applications in typography, hard-surface design, and generative models subject to custom constraints.
