Openscad DXF extrusion
- Details
- Published on Friday, 08 February 2013 18:21
- Written by Alex Davies
Finally got DXF extrusion working with openscad. Turns out it's actually pretty good at organic shapes, under the right circumstances.
Violin2 is an intersection of a scaled sphere and a rotational extrusion of "violin.dxf". It turned out pretty good.
{gallery}paperviolin{/gallery}
You can see a more in depth post on how I made it as well as download links for the source by clicking the post's title.
For most of my 3D modeling, I use openSCAD, the self-proclaimed "Programmers Solid 3D CAD Modeler". The main thing that differentiates it from all the other 3D software is that your entire model is defined in a text file, like html or the now defunct vrml. This offers a few advantages. For example, you can always tell what size something is, because you're actually typing out the size in millimeters. You can also define variables. For example, if you want to work in inches instead of millimeters, you just need to figure out how many millimeters are in an inch and put that into a variable. Now you can simply say "3*inch" (Three multiplied by how many millimeters are in an inch) to get three inches. You can use variables for a lot of other things as well. In my violin form I defined a variable called "length". Now, when I want a different size violin, I can simply change the value of that variable. There are more complicated objects that have variable for things like the number of teeth on a gear, or the class of stepper motor you plan on using.
It's not so good for models that aren't very mathematical. For example, people. You can define a face using math, but it's not going to be a simple or elegant equation, especially if you want to add exceptions for scars and other bits that aren't symmetrical. It's much easier to sculpt those kinds of things using a conventional modeler such as blender.
OpenSCAD has a limited number of primitive shapes, and none of them are in the shape of a violin. This means that if I wanted a violin shape, I had two options. I could build it up using the existing shapes I had access to or I could import a shape from inkscape. It was a lot easier to simply trace a violin. This gave me a completely flat, 2D, violin. But I needed a 3D shape. First I had to convert it to DXF though. After just saving it as a DXF file failed, I ended up using pstoedit, following this tutorial.
The first step was something called a rotational extrude. Imagine that you're standing the violin on its edge, and then you spin it. Every point that violin passes through remains solid, like it was leaving a trail.
Leaving a sort of weird cylinder thing. My next step wash to squash it down. Openscad has a "scale([x,y,z]);" function, so I just scaled it to 0.5 of its size on one axis.
Still not a violin, but it's getting closer. The final step was an intersection. That means the object only actually exists where two different objects overlap. I took a sphere, and squashed it down a lot. It's sort of like carving off any of the violin that stuck out of the sphere.
And that's it.
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