Parametric Boomerang in Blender and Geometry Nodes

prusaprinters

<p><i>(Edit: I added a new version geometry-nodes-3 which has a more asymmmetric airfoil and a slight change to the elbow section. I recommend using that one.)</i></p><p>There are multiple boomerangs made in Blender among my designs, but so far it wasn't possible (for me, at least) to make one that (a) can be manipulated via Bezier curves and (b) does not require special plugins such as <a href="https://github.com/nortikin/sverchok">Sverchok</a>.</p><p>I have made such parametric boomerangs with Sverchok in the past (see the remix section for references), but wasn't able to do so with stock Blender and geometry nodes.</p><p>In recent Blender versions, new geometry nodes such as <a href="https://docs.blender.org/manual/en/dev/modeling/geometry_nodes/mesh/extrude_mesh.html">Extrude Mesh</a> have been implemented. With these, it is now possible to make a working boomerang that can be manipulated after the fact by dragging around the control points of the Bezier curves.</p><p>The airfoil is kind of crude, since geometry nodes don't seem to be able to do bevels right now, but it works just fine.</p><p>Printed with lots of perimeters (I use 5), 4 top and bottom layers, and 25-30% infill at .2 layer height. Throw low and with a bit of layover. Should do a nice and easy 30 meter-ish circle. Works best in light to moderate winds.</p><h3>How I Designed This</h3><p>Made in Blender 3.2 Alpha, but 3.1 should work, too. Have a look at the geometry nodes in the .blend file to see how it's done. Here's the basic idea:</p><ul><li>Take in the two bezier curves for the outline and the shape of the top surface of the boomerang.</li><li>Convert both curves to meshes and fill the space between them with triangles. (I would prefer quads, but the <a href="https://docs.blender.org/manual/en/latest/modeling/geometry_nodes/curve/fill_curve.html">Fill Curve</a> node doesn't support that.)</li><li>Move the vertices from the inside curve upwards to create the airfoil.</li><li>Fill the inside curve with an n-gon to create the top surface of the boomerang.</li><li>Extrude the outside curve downwards to thicken the bottom of the airfoil.</li><li>Join all of these bits into one output mesh.</li></ul><p>One caveat: there's a parameter for the Bezier resolution, which needs to be set in the properties of the two curves as well as in the input properties of the geometry nodes. I have not been able yet to synchronize these properties automatically (with Drivers and whatnot), so if you change one you need to change the others as well.</p>