Win64, English

This is an application for Autodesk® Fusion 360™ in designing curves of high quality on criteria of smoothness.

General Usage Instructions

Several kinds of geometric determinant (GD) are used to specify the structure of the modeling curve:

1) The base polyline. The curve passes exactly through the vertices of the base polyline with shape preserving. Inflection points coincide with the points of inflection of base polyline. Sites of constant sign of curvature of the curve coincide with sites of constant sign of discrete curvature of base polyline. Discrete curvature of polyline at the vertex v [i] is defined as the analog of the curvature of the curve, where the first and second derivatives rd (t), r2d (t) are replaced by polyline central differences. For flat polyline the sign of discrete curvature is positive if the bypass of v [i-1] v [i] v [i + 1] is executed counter-clockwise.


2) The tangent polyline. The curve passes along polyline, touching links of polyline. The inflection points of the curve lie on the links of inflection of polyline. Link of inflection of a polyline divides polyline into sites with different signs of the discrete curvature. Sites of constant sign of curvature of the curve coincide with sites of constant sign of discrete curvature of a polyline.


3) GD Hermite of first order fixation (GD Hermite 1). GD is points with tangent vectors.


4) GD Hermite of second order fixation (GD Hermite 2). It is GD Hermite of first order fixation supplemented with vector-segments of curvature radii in each point.


After installation the add-in "FairCurveModeler" will create a new button in the menu of the "Model" workspace's "Add-Ins" panel. When the command is selected a command dialog is displayed where you are prompted to select objects and to set parameter. A command dialog consists of a list of command inputs. There are three selection inputs to select the points, tangents and radii; 6 drop-down text lists to set the modes for curve creation.


Select points and lines only of sketch.


The maximum number of vertices of the initial polyline - 64;


When constructing base polyline follow strict restrictions on the form of polyline:

- the angles between adjacent segments must be greater than 90 degrees;

- сlosed polyline is defined by at least 5 points / lines;

- unсlosed polyline is defined by not less than 3 points / lines;

- locally convex parts of polyline with points / lines of inflection are defined by not less than 4 points / lines;

- the inflection point of curve is defined by the midpoint of a two segmented part that divides a polyline into sites with different signs of orientation of form of polyline. This two segmented part must have a smaller angle than the adjacent two segmented parts (in particular midpoint of two segmented part can lie on a straight line);

- straight site of curve defined by 3 and more vertices strictly on the line.


When you specify a tangent polyline, a imaginary polyline that passes through the middles of links of tangent polyline must satisfy these strict restrictions.


When setting the fixed values of the curvature at the end points of the curve in mode (Approximation: [v] b-spline) the values of the curvature must be smaller (and values of the radii larger) than the values of curvatures (values of radii), which are determined in the GD Hermite 1 by default.


At approximation of v-curve by a b-spline curve of degree 8 on critical sections of polyline (sections with an abrupt change of curvature, transitions to the straightness) approximation error may be greater than a predetermined (0.000001). In this case, the application displays a warning.



Ribbon/Toolbar Icon Command Command Description


Basic command of Application. Command creates fair curves. Insert app in list of apps Add-Ins: Modeling space > Panel Add-Ins > Scripts and Add-Ins > My Add-Ins + > C:\Users\...\AppData\Roaming\Autodesk\Autodesk Fusion 360\API\AddIns\FairCurveModeler > FairCurveModeler.dll. Launch the app FairCurveModeler: Panel Add-Ins > Scripts and Add-Ins > Select FairCurveModeler > Run App prompts: FairCurveModeler is loaded successfully. A command is added to the Add-Ins panel in modeling space. Call Command: Modeling space > Add-Ins panel> Create fair curve. App displays the Command Dialog.


Install: simply double-click the MSI to install the app.


When you first run the Application or at the completion of the license term you must Activate product. The Application displays the message: "Please Register3D to activate the product. Your UserId: XXXXXXXXXXXX". The message contains the address of web-service and user ID. Go to the web-service by clicking on the Register3D. Read the text of the license. When registering on the web service use only the value of the message UserId: XXXXXXXXXXXX.

Press [to Code of Activation] in the 'Download the Code of Activation'. On the page 'CodeActivation3D' click [Download] button. Copy all the text from the window displayed. Press OK to the message in Autodesk® Fusion 360™. In Command Dialog under the 'Paste Code' section paste the copied text of Code Activation so as to activate the product.


To uninstall this plug-in, exit the Autodesk product if you are currently running it, simply rerun the installer, and select the "Uninstall" button.

OR, you can uninstall it from 'Control Panel\Programs\Programs and Features' (Windows 7/8/8.1), just as you would uninstall any other application from your system.

Additional Information

Scientific and program development information can be found under Author's site: http://spliner.ru


We are ready take consulting opportunities according to your requirements or technical projects to perform the development of FairCurveModeler to different CAD-systems and graphics packages.


We are ready to meet your requirements or your technical projects in developing specialized applications based on FairCurveModeler in designing the objects with functional curves and surfaces.


- For the tracing and profiling roads;


- For design of cam mechanisms;


- For design work surfaces of tillage machines;


- For design of outer surfaces of ships, aircraft, automobiles, architectural objects.

Known Issues


Company Name: RespectSoft
Support Contact: geometry@respectsoft.ru

Author/Company Information


Support Information

Support Information: geometry@respectsoft.ru


Version History

Version Number Version Description


Initial version
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