Optics: bound cache-only bright PSF splats

README.md

@@ -234,6 +234,14 @@ cached/direct-fallback image counts.  Pass `--psf-direct` to use the slower
 whose required HDR-tail support exceeds the cache radius selects that reference
 path automatically.
 
+For bounded preview renders, `--max-cache-psf-flux F` (default `1`) allows
+images with `1 < flux <= F` to use the existing cache instead of the direct
+evaluator. This does not rebuild or enlarge the cache: the image retains its
+true core flux, color, and sub-pixel position, while its Moffat wing is clipped
+at the existing cache radius. Images above `F` retain the direct fallback.
+`--max-magnification M` (default unlimited) caps the per-triangle rendering
+magnification before flux is formed; it is an explicit preview approximation.
+
 The PSF-cache completion line is printed before tracing and catalog splatting
 begin.  For long renders, pass `--verbose` to print catalog-prefetch state,
 splat-worker local heartbeats (8, 16, 32, ... completed triangles per worker),