The cottage doorway 'void' (dark cell + floating entities while the chase camera looks
through the opening): PortalProjection.ProjectToNdc clipped portals on w+z>=0 — the GL
[-1,1] near-plane test — but acdream's camera builds its projection with D3D-convention
Matrix4x4.CreatePerspectiveFieldOfView and a 1.0 m near plane (RetailChaseCamera). Against
that matrix w+z>=0 discards everything within ~0.5 m of the eye, so when the camera orbits
to ~0.1 m from a doorway portal the near edge is clipped, the far edge projects off-screen
([flap] showed p->0171 D=0.10 proj=4 clip=0 ndc Y=-3.5..-6.6), the room behind is culled
(vis=1) and only the tiny vestibule shell draws -> dark void. Rotating away moved the eye
off the portal -> vis=5 -> room rendered.
Fix: clip against the EYE (w > MinW, MinW=0.05 m), near-INDEPENDENT — a portal you're
standing in still projects (covers the screen) so the cell behind stays visible. We only
use the projected x/y for the visibility clip region, so keeping vertices in front of the
near plane is correct. Matches retail PView::GetClip near-clipping the portal before project.
RED->GREEN regression test (doorway 0.1 m from a near=1.0 eye); 177 App tests green; the
existing straddling ±50 bound still holds.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The clip predicate (w+z>=0) is convention-agnostic, not GL-specific:
Matrix4x4.CreatePerspectiveFieldOfView (which all acdream cameras use) is
NDC z in [0,1], not [-1,1]. Comment said "GL near plane / z_ndc>=-1" which
is misleading though the code is correct (eye w=0 always excluded; divide
safe under both conventions). Also soften the ProjectToNdc CCW claim: it
preserves projected winding; the caller must feed camera-facing portals.
No behavior change. (Opus code-review I-1/M-1.)
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
