6
1
Take as input 3 floating point numbers, which represent the x, y, z coordinates of a point. Return a truthy or falsey value indicating whether the point is inside the regular icosahedron centred at the origin, with top and bottom vertices at (0, 0, 1) and (0, 0, -1), and with one of the upper ring of middle vertices in the +X+Z quarterplane. Input/output formats can be anything reasonable. To allow for rounding error, Your code does not have to give correct answers for points within 10^-6 units of the boundary
Example inputs / outputs:
0, 0, 0 => true
1, 1, 1 => false
0.7, 0.5, -0.4 => true
-0.152053, -0.46797, 0.644105 => false
-0.14609, -0.449618, 0.618846 => true
To be absolutely clear on the orientation of the icosahedron, the coordinates of the vertices are approximately
{{0., 0., -1.},
{0., 0., 1.},
{-0.894427190999916, 0., -0.447213595499958},
{0.894427190999916, 0., 0.447213595499958},
{0.723606797749979, -0.5257311121191336, -0.447213595499958},
{0.723606797749979, 0.5257311121191336, -0.447213595499958},
{-0.723606797749979, -0.5257311121191336, 0.447213595499958},
{-0.723606797749979, 0.5257311121191336, 0.447213595499958},
{-0.27639320225002106, -0.85065080835204, -0.447213595499958},
{-0.27639320225002106, 0.85065080835204, -0.447213595499958},
{0.27639320225002106, -0.85065080835204, 0.447213595499958},
{0.27639320225002106, 0.85065080835204, 0.447213595499958}}
Scoring is standard code-golf; the fewest bytes wins.
6Nitpick: Standard code golf is fewest bytes, not fewest characters. The latter option allows compressing code by using all 2^32 Unicode characters. – Dennis – 2016-01-31T20:12:21.067