2025-07-01
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# EdgeFlow
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This addon adds operators to blender which help when dealing with curved shaped meshes.
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Feel free to create issues, file requests etc. but be aware of that I might not find time to work on this as much as I'd probably need to.
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## Installation
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Master is stable - adventures are in the Dev branch.
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The addon should work from blender 3.5+ and also work in the current blender release.
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* Get the latest EdgeFlow.zip release in: https://github.com/BenjaminSauder/EdgeFlow/releases
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* start Blender and open the user preferences
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* switch to the Add-ons tab and click the 'Install...' button
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* locate the downloaded EdgeFlow.zip file and double-click it to install
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* search for the addon "EdgeFlow"
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* activate the addon by ticking the checkbox (hit the Save User Settings button at the bottom if your blender is setup that way)
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#### Where are these located in blender?
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The operators can be accessed via the 3D View in the Mesh>Edge and Mesh>Vertex menu, the corresponding
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rightclick viewport context menus or the default shortcut Ctrl-E / Ctrl-V.
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## Tools
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### Set Flow:
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My stab at implementing a set flow operator for blender, which is a popular tool in many 3d applications. This adjusts the edgeloop via a spline interpolation such that it respects the flow of the surrounding geometry.
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The tool operates orthogonal to the direction of the flow of the edgeloop, indicated by the orange in the image.
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**Mix:** Blend between intial vertex positions and the interpolated result.
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**Tension:** Controls the strengh of offset.
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**Iterations:** How often the operation will be repeated.
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**Min Angle:** Cut off angle of the smoothing. Falls back to a linearely extrapolated position if the angle is beyond threshold.
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In this example the control points for the spline smoothing are around the corner - which creates a nasty bulge. With the min angle one can force the alghorithm to find a better solution.
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**Blend Mode:**
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- Absolute: Use a number of vertices along the edgeloop to control the blend length.
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- Factor: Blend length defined by a factor of the length from the edgeloop.
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**Blend Start:** Number of vertices from the start of the edgeloop | The partial length from the start of the edgeloop.
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**Blend End:** Number of vertices from the end of the edgeloop | The partial length from the end of the edgeloop.
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**Blend Curve:** Linear or Smoothstep blend of the values along the edgeloop.
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Notice how the shape changes from straight to curved at the right image. This obviously only works for edgeloops which are not cyclic.
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### Set Linear:
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This makes each selected edge loop a straight line between start and end point. The spacing of all the other points can either be spaced evenly, or projected from the original distances.
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The tool operates in the direction of the flow of the edgeloop, indicated by the green in the image.
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**Space evenly:** Place the vertices on the loop in regular distances.
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### Set Curve:
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This tool curves each selected edge loop onto a spline which is controled by the first and the last edge of the edgeloop.
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The tool operates in the direction of the flow of the edgeloop, indicated by the green in the image.
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**Mix:** Blend between intial vertex positions and the interpolated result.
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**Tension:** Controls the strengh of offset.
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**Use Rail:** Customize the interpolation by using the first and last edge of the edgeloop to control the curvature.
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**Rail Mode:** Switch rail mode between using absolute units or a factor of the length of the edge.
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**Rail Start:** Choose how long the rail is at the start.
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**Rail End:** Choose how long the rail is at the end.
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### Set Vertex Curve:
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This tool moves vertices to a curve based on vertex selections. The picking order of the selected vertices defines the outcome of the tool.
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So it's very important to select in the correct order.
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- **2 vertices are selected:** a half circle is constructed between the points.
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- **3 vertices are selected:** all inbetween points are placed onto a circle which goes through the selected points. You can think of it as start - middle - end points in the selection.
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- **4 or more vertices are selected:** the tool constructs a spline and projects all points onto it.
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**Tension:** Controls the strengh of offset
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**Use Topology Distance:** Force the path search to ignore edge lenghts, so only topological distance is used to find the inbetween vertices.
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**Flip Half Circle:** (only for 2 vertices) Flip the direction of the half circle.
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**Rotate Half Circle:** (only for 2 vertices) Rotate the half circle orthogonal to the intial orientation.
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**Space evenly:** (only for 3 or more vertices) Place the vertices in even distances.
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## How Set Flow works
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Back when I first got to see this in action I did quite not understand how it all worked - so I thought it might be well worth adding a quick description to better understand how the underlaying mechanics work.
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The tool goes over each edge from an edgeloop, and then goes over each vert for this edge. For every vert it searches the points C1-C4 which are used as 'control points' for the spline interpolation - quite similar to how every vector drawing programm works.
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So its all depending on the surrounding geometry - which also means if we have multiple neighbouring edgeloops they all influence each other once we start applying this smoothing. Doing the same operation a few times helps to balance it all out and converges quickly into something stable after a few iterations - so hence the need for such an option.
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# Credits
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Maintainer:
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Benjamin Sauder
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Additional contributions:
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- IngoClemens
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- ora-0
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## Developer Notes
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I had to reimplement the edge loop selection from blender because I needed to go from a spaghetti edge selection to sorted edgeloops. While I like that I was able to reproduce blenders selection behaviour I still think I might have overlooked something on how to do it with the regular api - any hints?
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I tried different spline interpolation implementations but settled with a hermite interpolation from http://paulbourke.net/miscellaneous/interpolation/ as it has this nice tension variable.
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