Softer shadows in raytracing and RTAO - #7653
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please dont forget there is another shadowCascadeParams in shadow_map-g |
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…ular size 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 <noreply@anthropic.com>
The shadow-mapped path's penumbra width was a fixed per-cascade value (shadow_smoothness_scale()'s ceiling), so every occluder blurred its shadow by the same amount regardless of how close it actually was to the receiver -- unlike the raytraced path, which gets that for free from traceShadowRayCone()'s real occluder distance. Close that gap with PCSS: search nearby texels for occluders, then scale the filter radius by how far away they were. The blocker search (pcssBlockerSearch() in shadows.sdr) needs raw, uncompared depth reads, which the existing PCF sampler can't do -- it's bound with a compare mode for the hardware shadow-compare instructions the filtered sampling itself relies on. So shadow maps now get a second sampler, shadow_map_raw, bound to the same texture with compare mode off; on OpenGL that needs a second sampler object and GL 3.3 (shadow_contact_hardening_supported()), Vulkan can always bind it. Where the raw sampler isn't available, or the new Graphics.ShadowContactHardening option is off, shadows_start_render() sets Shadow_penumbra_scale[cascade] to -1 as a sentinel and pcssPenumbraRadius() (shadows.sdr) falls straight back to the fixed radius, bit-identical to the pre-contact-hardening behavior and skipping the extra texture reads. When it is on, shadows_start_render() computes each cascade's penumbra scale from its own frustum extents and the sun's tanθ; the shader turns that plus the blocker search's average depth into a per-pixel radius, clamped to [1 texel, the old fixed ceiling]. A blocker search that finds nothing doesn't fall back to "no shadow" -- a sparse 8-tap search can miss a thin occluder, so it instead runs the full filter at the hardest (1-texel) radius, trading a touch of extra blur for not popping a real shadow to nothing. Drops RT_SHADOW_SUN_SIZE_CALIBRATION accordingly: that constant existed only to fake a blocker-distance-driven penumbra on the shadow-mapped path by pre-scaling the raytraced cone to match it, and the shadow-mapped path now has a real blocker search of its own, so the raytraced cone goes back to its physically correct size.
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Adds methods for softening RT shadows. This mechanism works by setting an apparent light size either in the mission file, a lab override, or by deriving it from the sun bitmap. The current implementation limits the apparent size to 1.5°; this is an artificial constraint based around the limits of raytraced shadows - the wider the sun is, the sparser the rays to check whether something is in shadow become, and the more grainy the shadows appear.
There are table settings and FRED/qtFRED controls to set this in missions.
And because the methods required to do soft shadows are mostly identical to what you need to do in order to do raytraced Ambient Occlusion, I threw in that effect as well - but I seriously cannot recommend anyone use it. The visual impact is only noticeable when you really look for it, and the performance cost is pretty large.