The committed Phase 1 code rendered a black screen due to three
independent bugs, fixed here:
- black_hole.wgsl: dt was sized as |eye|/steps, so the full integration
only traveled |eye| units total — rays never reached capture or escape
and every pixel fell through to accum=black. Now dt covers
eye_dist + escape_r across the configured step count, and the escape
test uses the dynamic escape_r instead of a hardcoded 1000.0.
- render/plugin.rs: the planets binding was Handle::default(), causing
AsBindGroup to return RetryNextUpdate every frame and silently skip
the fullscreen quad's draw. Pre-fill a MAX_PLANETS-sized zeroed
ShaderBuffer at startup so the binding resolves immediately.
- render/plugin.rs: scale the fullscreen quad by half the window size
to match Camera2d's default WindowSize projection (1 unit = 1 px);
the old aspect-based scaling letterboxed the image.
- render/plugin.rs: add nudge_camera to work around Bevy 0.19 #24448,
where a static camera stops rendering after the first frame.
- planets.wgsl: rotate world-space planet centers into disk-local space
before the ray-sphere test (ray and centers were in different spaces).
The whole-file #import "file.wgsl" form (without ::) does not reliably
bring functions into scope in naga_oil/Bevy 0.19 — the renderer was
failing at runtime with 'no definition in scope for identifier:
ray_direction' (and rot_x, deriv, etc.), producing a blank screen despite
'cargo build' passing (shaders aren't compile-checked at build time).
Fix: add #define_import_path to each module file and import symbols
explicitly via namespace::name (the canonical Bevy pattern from the
shader_material_2d example). Verified the full shader pipeline compiles
and runs at runtime with zero WGSL errors.
This was a pre-existing bug masked by incomplete runtime verification in
earlier tasks; it is NOT specific to Task 15's grid work. All earlier
visual features (shadow, Doppler disk, Einstein halo, stars, planets,
grid) now actually render.
Add planets as ray-traced spheres inside the RK4 geodesic loop. A new
planets.wgsl shader tests each integrator segment against a storage
buffer of SphereData (center/radius/color/emissive) and composites hits
front-to-back alongside the accretion disk. Lambert shading with a fixed
light direction; emissive flag bypasses shading.
- assets/shaders/planets.wgsl: segment-sphere intersection + shading
- src/scene/: Planet component, upload_planets system, default planet
- black_hole.wgsl: wire planet_hit into the compositing loop
- geodesic_schwarzschild.wgsl: replace tuple return with Deriv struct
