Transform the sphere by a matrix: the centre like a point, the radius by the largest scale factor of the matrix (the length of its longest column). Exact for uniform scale, a safe overestimate otherwise.
Grow the radius, keeping the centre, until the sphere contains point
Grow the radius, keeping the centre, until the sphere contains other
The sphere around a box: its centre and half its diagonal. Loose for
round shapes (up to √3 times the true radius); see
BufferGeometry.computeBoundingSphere() for the tight version.
A bounding sphere: a
centerand aradius. A negative radius marks an empty sphere, which is what a new sphere starts as. Unlike a box, a sphere is unchanged by rotation, which makes it the cheap choice for anything that happens in world space: framing a camera, culling, a first pass of picking.Operations work in place and return
this.