Automatic 2d Fillet in OpenSCAD

thingiverse

// This script creates a smooth curve between two arbitrary shapes. // It works by blowing up each shape by a fixed distance and then creating an extremely thin shell around these enlarged shapes. These shells are then intersected to give one point along the curve. These distances are chosen so that, for two shapes that meet at right angles, these intersection points fall on a quarter circle, with 16 facets. // The hull() function is then used to connect two adjacent intersection points together, thus creating the curve. // This method has two side effects: // The curve does not exactly follow the two shapes but juts out slightly by 0.005, which is the thickness of the shells used to create the intersection points. // secondly, this script creates a slight bulge around places where the two original shapes overlap. As illustrated in example 5 and example 6. This excess bulge needs to be manually removed by trimming. // Sometimes it is possible to avoid this excess bulge by making an intelligent choice of the shapes; any extra curve created can then be blocked out by a third shape, as shown in example 7. // // The curve follows a circular form for straight shapes that meet at right angles. However, if the edge of one or both shapes is not a straight line (e.g. creating a fillet between two circles) the resulting curve will not be perfectly round and may have an inaccurate specified radius. For shapes with straight edges but meeting under non-perpendicular angles, similar distortions occur. // The display_routine() function displays the original two shapes in red and green. They are moved by 0.01 in z-direction to prevent z-buffer clashes on F5. This displacement in z-direction does not affect the result of F6. As this result is purely two-dimensional, moving the objects in z-direction will not have an effect. The fillet created between the original shapes is displayed in a yellow color. // // The parameter mink_radius=16 determines how rounded the curve that blows up the shapes and creates shells. A higher number can greatly increase computation time. It can be reduced as low as 4 to speed up processing, but this will result in slightly irregular curves. The dr_threshold =0.005 value defines the thickness of these shells. Reducing it too much will cause there to be no calculated intersection between shells and the fillet creation algorithm may fail completely. // Increasing computation time with more complex shapes is significant, nearly exponential in relation to number of faces. Replacing or optimizing functions could greatly speed up overall calculation performance; a potential replacement strategy might be shifting shape parts along slightly different direction every repetition union of the expanded result would still work perfectly.