The GLSL is generated from the HLSL by one lowering, mirrored against C# by a
committed fixture evaluated on its own arguments (portable across OSes), with
the frustum ball checked by two-sided enclosure and Phacelle by a scaled
absolute bound. design.md conflict: keeps the branch's sqrt-precision text and
drops the 6e-4 sentence interval-ops r4 removed.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>