From e8caa58b08819b668d865f0386feb881174434af Mon Sep 17 00:00:00 2001
From: Nolan Darilek <nolan@thewordnerd.info>
Date: Tue, 28 Sep 2021 14:36:21 -0500
Subject: [PATCH] Optimize visibility.

---
 src/visibility.rs | 63 +++++++++++++++++++++++++++++++++--------------
 1 file changed, 44 insertions(+), 19 deletions(-)

diff --git a/src/visibility.rs b/src/visibility.rs
index 305277b..440e820 100644
--- a/src/visibility.rs
+++ b/src/visibility.rs
@@ -3,7 +3,7 @@ use std::{
     collections::{HashMap, HashSet},
 };
 
-use bevy::prelude::*;
+use bevy::{core::FixedTimestep, prelude::*};
 use bevy_rapier2d::{na, na::UnitComplex};
 use coord_2d::{Coord, Size};
 use derive_more::{Deref, DerefMut};
@@ -241,10 +241,10 @@ fn update_viewshed_for_coordinates(
     if !config.query_pipeline_active {
         return;
     }
-    for (visible_entity, coordinates) in visible.iter() {
+    for (visible_entity, visible_coordinates) in visible.iter() {
         for (viewer_entity, mut viewshed, mut visible_entities, start) in viewers.iter_mut() {
             if viewer_entity == visible_entity
-                || coordinates.distance(start) > viewshed.range as f32
+                || start.distance(&visible_coordinates) > viewshed.range as f32
             {
                 continue;
             }
@@ -265,10 +265,20 @@ fn update_viewshed_for_coordinates(
     }
 }
 
+#[derive(Clone, Debug, Deref, DerefMut)]
+struct LastStart((i32, i32));
+
 fn update_viewshed_for_start(
+    mut commands: Commands,
     config: Res<RapierConfiguration>,
     mut viewers: Query<
-        (Entity, &mut Viewshed, &mut VisibleEntities, &Coordinates),
+        (
+            Entity,
+            &mut Viewshed,
+            &mut VisibleEntities,
+            &Coordinates,
+            Option<&LastStart>,
+        ),
         Changed<Coordinates>,
     >,
     map: Query<&Map>,
@@ -280,19 +290,30 @@ fn update_viewshed_for_start(
     if !config.query_pipeline_active {
         return;
     }
-    for (viewer_entity, mut viewshed, mut visible_entities, start) in viewers.iter_mut() {
-        if let Ok(map) = map.single() {
-            update_viewshed(
-                &viewer_entity,
-                &mut viewshed,
-                &mut visible_entities,
-                start,
-                &*query_pipeline,
-                &collider_query,
-                map,
-                &visible,
-                &mut changed,
-            );
+    for (viewer_entity, mut viewshed, mut visible_entities, start, last_start) in viewers.iter_mut()
+    {
+        let should_update = if let Some(last) = last_start {
+            start.i32() != **last
+        } else {
+            true
+        };
+        commands
+            .entity(viewer_entity)
+            .insert(LastStart(start.i32()));
+        if should_update {
+            if let Ok(map) = map.single() {
+                update_viewshed(
+                    &viewer_entity,
+                    &mut viewshed,
+                    &mut visible_entities,
+                    start,
+                    &*query_pipeline,
+                    &collider_query,
+                    map,
+                    &visible,
+                    &mut changed,
+                );
+            }
         }
     }
 }
@@ -403,8 +424,12 @@ impl Plugin for VisibilityPlugin {
         app.add_event::<VisibilityChanged>()
             .add_system(add_visibility_indices.system())
             .add_system_to_stage(CoreStage::PostUpdate, viewshed_removed.system())
-            .add_system(update_viewshed_for_coordinates.system())
-            .add_system(update_viewshed_for_start.system())
+            .add_system_set(
+                SystemSet::new()
+                    .with_run_criteria(FixedTimestep::step(0.25))
+                    .with_system(update_viewshed_for_coordinates.system())
+                    .with_system(update_viewshed_for_start.system()),
+            )
             .add_system_to_stage(CoreStage::PostUpdate, remove_visible.system())
             .add_system_to_stage(CoreStage::PostUpdate, update_revealed_tiles.system())
             .add_system_to_stage(CoreStage::PostUpdate, log_visible.system());