Raytraced shadow penumbras needed a hand-authored $SunAngularSize: in
stars.tbl, which no shipped content sets -- so in practice nothing ever
got a penumbra, and the shadow-mapped path's $Shadow Smoothness Factor:
had no relation to it at all. Derive a size from the sun bitmap instead
and drive both methods from the same number.
g3_render_rect_screen_aligned_2d() sizes the sun quad so its rad is the
tangent of the half-angle it subtends, making tan(angular radius) equal
to 0.05 * the mission's +Scale: * the emitting disc's fraction of the
bitmap. That fraction is the area of the pixels at or above 90% of the
brightest one, converted to an equivalent radius. Across 90 sun bitmaps
from retail, the MediaVPs, Blue Planet and BtA it lands at a median of
0.261 (retail's chunkier art at 0.487), and the threshold acts as a
constant factor rather than a per-bitmap judgement call -- Spearman rho
0.96 between a 90% and a 50% cutoff.
Taken literally that yields suns 3.9-8.5x Sol's apparent diameter once
+Scale: is folded in (median 1.55, up to 5.0 in retail's own missions),
so the measurement is scaled by 0.25 and clamped to 1.5 degrees, putting
typical content near Sol. Derivation is the default: $SunAngularSize: 0
asks for hard shadows, an explicit value still wins, and missions can
also set +AngularSize: on an individual sun to override both, with FRED
and QtFRED UI (validation and fallback included) to author it. Bitmaps
that can't be read -- and the deliberately blank sun bitmaps mods ship
to get a light source with no visible disc -- fall back to hard shadows
rather than to the widest possible penumbra.
That angular size now sizes the raytraced penumbra cone directly
(traceShadowRayCone() in shadows.sdr), with sample count following the
same Shadow_quality tier that picks the shadow map's resolution (1 ray
at Low, up to 16 at Ultra) rather than being a separate setting. The
shadow-mapped path's tabled smoothness values were tuned by eye against
Sol-sized retail/MediaVPs art, so shadow_smoothness_scale() in
shadows.cpp scales them by the active sun's size relative to Sol,
clamped to what the shadow map can represent (shadow_clamp_smoothness()).
The two methods still disagree about occluder distance -- the raytracer
uses the real one, the shadow map's tabled values stand in for a blocker
distance pinned to the cascade's own extent -- so RT_SHADOW_SUN_SIZE_CALIBRATION
in shadows.sdr is a constant factor that makes a given $SunAngularSize:
read as roughly the same softness either way; it's the number to revisit
if the shadow map ever grows a real blocker search.
Also adds RTAO (raytraced ambient occlusion) sharing the same TLAS as
the shadow rays, with lighting-profile-driven radius/strength, and lab
controls for RT shadow quality (Low/High), the local light cap, RT
shadow samples, RTAO, and an angular-size override for comparing both
shadow methods against the same sun. All are safe to change live: they
only gate which lights are picked as shadow casters or scale existing
uniforms while filling the per-frame light data.
Co-Authored-By: Claude Opus 5 <[email protected]>
