% The unit sphere — the reference case.
%
% A geometry file defines shape(theta, phi, ...) -> gx, gy, gz: the surface
% over the solver's grid (all npts x 1), compiled to WebGPU like the models.
% The host analyses the result into spherical-harmonic coefficients,
% band-limited at lmax.

function [gx, gy, gz] = shape(theta, phi)
  st = sin(theta);
  gx = st .* cos(phi);
  gy = st .* sin(phi);
  gz = cos(theta);
end