Fixing the tetrahedric gnomonic requires specially modified versions of d3-geo and d3-geo-projection to handle clipPolygon().
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](https://github.com/Fil/) Questions and comments welcome on [gitter.im/d3](https://gitter.im/d3/d3), [twitter](https://twitter.com/@recifs) or [slack](https://d3js.slack.com).
forked from Fil‘s block: Lee’s Tetrahedric Conformal Projection