Deduplicate redundant FOV computation #292

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opened 2026-03-08 20:18:41 +00:00 by john · 1 comment

john commented

2026-03-08 20:18:41 +00:00

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Problem

FOV is computed 2-3x per visibility update cycle:

apply_perspective() → drawFOV() calls grid->computeFOV()
entity.update_visibility() calls grid->computeFOV() again
updatePerspective() → drawFOV() triggers a third computation

This is pure redundant work — entity position hasn't changed between these calls.

Discovered during

7DRL 2026 jam — observable as unnecessary CPU cost on grids with large FOV radii.

Proposed fix

Add a dirty flag to the grid's FOV state. Mark dirty when the perspective entity's position changes (or when walkable/transparent data changes). computeFOV() early-returns if not dirty. This ensures at most one FOV computation per frame regardless of how many code paths request it.

Alternative: deduplicate the call sites directly so only one path triggers computation per frame. The dirty flag approach is more robust against future call site additions.

Scope

This is independent of #252 (Grid/GridView overhaul) and can be fixed incrementally on the current codebase.

## Problem FOV is computed 2-3x per visibility update cycle: 1. `apply_perspective()` → `drawFOV()` calls `grid->computeFOV()` 2. `entity.update_visibility()` calls `grid->computeFOV()` again 3. `updatePerspective()` → `drawFOV()` triggers a third computation This is pure redundant work — entity position hasn't changed between these calls. ## Discovered during 7DRL 2026 jam — observable as unnecessary CPU cost on grids with large FOV radii. ## Proposed fix Add a dirty flag to the grid's FOV state. Mark dirty when the perspective entity's position changes (or when walkable/transparent data changes). `computeFOV()` early-returns if not dirty. This ensures at most one FOV computation per frame regardless of how many code paths request it. Alternative: deduplicate the call sites directly so only one path triggers computation per frame. The dirty flag approach is more robust against future call site additions. ## Scope This is independent of #252 (Grid/GridView overhaul) and can be fixed incrementally on the current codebase.

john added the

Bugfix

system:grid

system:performance

priority:tier1-active

labels

2026-03-08 20:19:30 +00:00

john commented

2026-03-15 20:18:02 +00:00

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Roadmap context

Part of the Grid & Entity Overhaul Roadmap (docs/GRID_ENTITY_OVERHAUL_ROADMAP.md), Phase 1 (Foundation). The fov_dirty flag pattern introduced here is reused by #303 (FOV optimization for behavior triggers) in Phase 3.

## Roadmap context Part of the Grid & Entity Overhaul Roadmap (`docs/GRID_ENTITY_OVERHAUL_ROADMAP.md`), **Phase 1** (Foundation). The `fov_dirty` flag pattern introduced here is reused by #303 (FOV optimization for behavior triggers) in Phase 3.

john referenced this issue

2026-03-15 20:18:48 +00:00

FOV optimization for behavior TARGET triggers #303

john referenced this issue from a commit

2026-03-16 11:21:02 +00:00

Phase 1: Safety & performance foundation for Grid/Entity overhaul

john closed this issue

2026-03-16 11:21:02 +00:00