Stereographic Projection

thingiverse

I had a blast with this one, and I highly recommend checking out https://www.thingiverse.com/threonin/ for other amazing Stereographic Projection examples. This writeup explains how to use OpenSCAD's design with dxf files. ### Instructions 1. Find a black and white pattern you want to vectorize. It's easier if there aren't many grays, but you can skip this step if you already have a monochrome vector pattern. * I just searched for "black and white pattern". * Save the pattern to your computer. 2. Inkscape Directions 1. Open a new file in Inkscape (0.92) and import the imagefile. Don't open it, as this can crash Inkscape. A png is good, but jpeg is less ideal. 2. Use the Menu -> Path -> Trace Bitmap tool. a. Make sure the image is selected for the tool to work. b. I used the "Brightness Cutoff" option with Threshold: 0.45. You'll want to experiment with these options to find what works best for your pattern. c. The new pattern will be dropped on top of or underneath the original image, so drag it off the imported bitmap image. d. Type F2 to select the edit pathnodes tool and delete the other one. e. Next, we need to break up the paths into small pieces with Menu -> Extensions -> Modify Path -> Flatten Beziers. f. This breaks curved lines into bite-sized pieces because OpenSCAD doesn't like dxf splines. If you have curves, this step is not optional. g. The smaller "Flatness" variable is, the more segments, so I used '0.1'. Picking numbers greater than 1 will result in chunky rather than smooth shapes. h. Verify it by hitting F2 again and save the file to svg (Inkscape's native format). i. Resize the Page with Menu -> File -> Document Properties a. Make sure the page size fully encompasses the pattern. Inkscape will cut off things that aren't on the page. b. I sized the page to exactly match the pattern size in px. c. Then use the Menu -> Object -> Transform tool to move it exactly to (0,0) and uncheck 'Relative'. j. You can check the Layer name from Menu -> Layer -> Layers... For my scad-file, you want it to be "Layer 1". k. Save As filetype .dxf 3. OpenSCAD 1. When importing, OpenSCAD reads from the same directory as the scad file is in, but you can also use a full filepath. I was impatient, so my example assumes the dxf is sitting in the same directory as it. 2. It's helpful to know the size of the original image. 3. I left helpful comments in the code to show you which variables to modify with what information. Feel free to take out the Support Legs if they're a bad fit for your pattern. Also, this took literally 35 minutes to compile the stl, so be prepared.