Analytic-gradient simplex noise, ported from webgl-noise's
noise3Dgrad.glsl differentiation but retargeted onto this repo's own
snoise(float3) constants (0.6 falloff radius, +1 permute offset, 42
scale) so snoise_grad.w stays exactly snoise's own field. fbm_grad and
ridged_grad are octave sums with per-octave frequency/amplitude
compounding (invariant 8). octaves is clamped to [0, 16] so the HLSL
mirror test's full-int32-range oracle cannot turn a garbage octave
count into a multi-billion-iteration loop.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
e87dcc9ec5