Merge remote-tracking branch 'origin/server'

decisions/perception.md

@@ -102,6 +102,34 @@ How the player observes and interacts with the world: camera, fog, line-of-sight
 - **Raised by:** Araminta (Round 1 proposal, color palette design), project lead (approved, directive #2)
 - **Dissent:** None
 
+### D-035: Symmetric shadowcasting (Albert Ford) selected for LOS computation
+- **Date:** 2026-02-11
+- **Decision:** Albert Ford's symmetric shadowcasting algorithm is selected for all line-of-sight computation. The traditional recursive shadowcasting algorithm is rejected.
+- **Resolves:** Q-018
+- **Benchmark results (debug build, 1000 iterations, range 20):**
+
+| Map | Density | Symmetric | Recursive | Speedup |
+|-----|---------|-----------|-----------|---------|
+| 32x32 | open | 920µs/call | 1118µs/call | 1.2x |
+| 32x32 | 10% walls | 845µs/call | 4003µs/call | 4.7x |
+| 32x32 | 30% walls | 334µs/call | 2099µs/call | 6.3x |
+| 64x64 | open | 929µs/call | 1114µs/call | 1.2x |
+| 64x64 | 10% walls | 745µs/call | 4060µs/call | 5.5x |
+| 64x64 | 30% walls | 215µs/call | 1716µs/call | 8.0x |
+| 150x150 | open | 919µs/call | 1102µs/call | 1.2x |
+| 150x150 | 10% walls | 615µs/call | 3347µs/call | 5.4x |
+| 150x150 | 30% walls | 163µs/call | 1709µs/call | 10.5x |
+
+- **Key findings:**
+  - Symmetric is 1.2-10.5x faster across all configurations (debug build; release will be significantly faster)
+  - Advantage increases with wall density — more occlusion means less work for the quadrant-based approach
+  - Map size has minimal effect on relative performance at range 20 (both algorithms are bounded by vision range, not map size)
+  - All values well within the 100ms tick budget (D-026), even in debug
+  - Symmetry property verified: if A sees B, then B always sees A — critical for D-011's requirement that NPCs use the same perception system as the player
+- **Implementation:** Uses rational fraction slopes (`num/den` integer pairs) to avoid floating-point drift. Processes 4 cardinal quadrants with coordinate transforms. The production API is `compute_fov(is_opaque, origin_x, origin_y, range, z_level) -> VisibilityMap`.
+- **Raised by:** Dudley (implementation + benchmark), Tyre (technical direction)
+- **Dissent:** None
+
 ---
 
-*7 decisions. Last updated: 2026-02-11*
+*8 decisions. Last updated: 2026-02-11*

decisions/questions.md

@@ -89,7 +89,7 @@ Tracked questions awaiting discussion or resolution.
 - **Source:** Content Gap Analysis Workshop (Gestalt R2)
 
 ### Q-018: Shadowcasting algorithm selection
-- **Status:** Open
+- **Status:** Resolved → [D-035](perception.md#d-035-symmetric-shadowcasting-albert-ford-selected-for-los-computation)
 - **Question:** Which line-of-sight algorithm should be used? Symmetric shadowcasting (Albert Ford) vs recursive shadowcasting. Both are proven but differ in symmetry properties (symmetric: if A sees B, then B sees A) and implementation complexity. Requires benchmarking at 150x150 map scale with 30 entities to validate performance within 100ms tick budget.
 - **Context:** D-011 mandates LOS shadowcasting for fog of perception. Architecture review identified this as unspecified (audit section 2.2). Critical for Sprint 2 perception pipeline.
 - **Assigned to:** Tyre, Dudley