## Teaching in public

Lin Xin-Liang (林信良, 1975–2022) was known to Chinese-language programmers as **良葛格**, to JavaWorld@TW readers as **caterpillar**, and to the OpenSCAD community as **JustinSDK**. Those names belong to one continuous body of work: learning difficult technical ideas, explaining them in public, and turning the reusable parts into tools for other people.

Lin maintained [良葛格學習筆記](https://openhome.cc/), or openhome.cc, and published more than a thousand technical documents across C, C++, Java, Ruby and Rails, Python, JavaScript, Haskell, and other subjects. He worked as a technical consultant at a Sun Microsystems training centre, served as an authorized Oracle instructor, moderated JavaWorld@TW, and wrote or translated a substantial catalogue of programming books.[1][2][3]

In April 2012 he began the 程式人 column for iThome. The publication's memorial collection records 459 columns over ten years—more than one million Chinese characters—covering programming practice, mathematics, algorithms, learning, and the culture around software development.[1][2] This scale matters because dotSCAD did not emerge separately from his teaching. It applied the same habit: identify the difficult, reusable idea; give it a clear interface; and leave an example that another person can change.



## From algorithms to geometry

Lin's later iThome writing makes the connection between education and computational design especially visible. In [“Sources of inspiration for algorithmic creation”](https://www.ithome.com.tw/voice/153089), he described a treble-clef dragon built by combining an Archimedean spiral, Catmull–Rom curves, path-following operations, and a cosine-controlled body. The finished dragon is expressive, but the method is also a lesson: complex form can come from a small vocabulary of understandable mathematical operations.[4]

Other columns followed the same pattern. His writing on [L-systems](https://www.ithome.com.tw/voice/137795) moved from formal grammars and turtle graphics to reusable fractal-generation processes.[5] His article on [alpha shapes](https://www.ithome.com.tw/voice/153629) examined how a parameter changes the boundary recovered from a point set.[6] A discussion of [Sierpiński triangles](https://www.ithome.com.tw/voice/153229) connected the chaos game and iterated function systems with forms that extend naturally into three dimensions.[7]

Taken together, these articles show a consistent idea: algorithmic creation turns learning itself into a source of visual form. dotSCAD brought that idea into an OpenSCAD library.



## dotSCAD: a reusable mathematical vocabulary

[dotSCAD](https://github.com/JustinSDK/dotSCAD) describes its purpose directly: reduce the burden of mathematics and algorithms when working in OpenSCAD. Its public modules and functions are organized so a modeller can use one focused operation without having to reproduce the derivation behind it.[8]

The library ranges from familiar construction helpers—rounded solids, arcs, lofts, and sweeps—to a much broader computational-design vocabulary. It includes Bézier and B-spline paths, Archimedean and golden spirals, helixes and torus knots; transformations and cross-section generation; turtle graphics and two- and three-dimensional L-systems; noise, mazes, voxels, Voronoi structures, triangle algorithms, point sampling, polyhedra, and surface tools.[8][9]

This breadth is what makes dotSCAD historically interesting. It is not just a folder of shortcuts. Its structure reads like a curriculum for code-driven geometry: paths become cross-sections, cross-sections become surfaces, formal rules become drawings, and mathematical processes become editable models.



## Try a dotSCAD idea

The quickest way to understand Lin's approach is to move from reading into a working model. Varcad's JustinSDK projects mount dotSCAD as a library, preserve the original source structure, and let readers edit parameters while watching the geometry change.

The featured study below focuses on the core operation in Lin's [twist_bottle.scad](https://github.com/JustinSDK/dotSCAD/blob/master/examples/spiral/twist_bottle.scad) example. The displayed code is an excerpt rather than a standalone program; the complete upstream source defines the selectable profiles and inner container. The Varcad gallery provides a runnable collection of preserved examples, while the focused quickstart introduces the same library with a smaller rounded-cube model.



## Continuing influence

Lin died in 2022 at the age of 48. iThome assembled a memorial collection around his writing, and TVBS reported on programmers who remembered learning from his articles.[1][10] In the OpenSCAD community, remembrances emphasized both his technical range and the playful ambition of models such as dragons and programmatically generated mazes.[11]

The most useful way to carry that influence forward is not to treat the models as static pictures. They should remain inspectable programs. A reader should be able to follow a curve into its source, change a parameter, render the result, and reuse the technique in a different design.



## References

1. [林信良紀念專輯](https://www.ithome.com.tw/caterpillar), iThome, accessed August 25, 2026.
2. [林信良](https://www.ithome.com.tw/users/%E6%9E%97%E4%BF%A1%E8%89%AF), iThome author profile and article archive, accessed August 25, 2026.
3. [良葛格的Java之路：做有把握的事](https://www.ithome.com.tw/tech/52848), iThome, December 30, 2008.
4. [演算創作的靈感來源](https://www.ithome.com.tw/voice/153089), iThome, September 19, 2022.
5. [碎形與L-system](https://www.ithome.com.tw/voice/137795), iThome, May 28, 2020.
6. [從凹包到alpha shape](https://www.ithome.com.tw/voice/153629), iThome, October 17, 2022.
7. [構造謝爾賓斯基三角](https://www.ithome.com.tw/voice/153229), iThome, September 26, 2022.
8. [dotSCAD 3.3](https://github.com/JustinSDK/dotSCAD), GitHub repository and API reference, accessed August 25, 2026.
9. [dotSCAD documentation](https://justinsdk.github.io/dotSCAD/), JustinSDK, accessed August 25, 2026.
10. [程式達人「良葛格」驚傳離世！全網悼：看他文章受益良多](https://news.tvbs.com.tw/life/1964441), TVBS News, November 16, 2022.
11. [JustinSDK / Lin Xin-Liang / 良葛格 (1975–2022)](https://www.reddit.com/r/openscad/comments/yzwdcp/justinsdk_lin_xinliang_liang_gege_19752022/), r/openscad community memorial, November 2022. Community comments are used here as qualitative evidence of influence, not as biographical authority.
12. [OpenSCAD Advent Calendar 2022](https://openscad.org/advent-calendar-2022/), OpenSCAD.

Ideas built in code and geometry.

Lin Xin-Liang (JustinSDK), dotSCAD, and Code-Driven CAD