From 0751cf344d239eddb7e26ff4ff2de7e6dd894a56 Mon Sep 17 00:00:00 2001
From: Nolan Darilek <nolan@thewordnerd.info>
Date: Thu, 17 Mar 2022 12:15:30 -0500
Subject: [PATCH] Cache collision data when calculating visibility.

---
 src/visibility.rs | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/visibility.rs b/src/visibility.rs
index de3d3d8..3275229 100644
--- a/src/visibility.rs
+++ b/src/visibility.rs
@@ -4,7 +4,10 @@ use std::{
     marker::PhantomData,
 };
 
-use bevy::{core::FixedTimestep, prelude::*};
+use bevy::{
+    core::{FixedTimestep, FloatOrd},
+    prelude::*,
+};
 use bevy_rapier2d::{na, na::UnitComplex};
 use coord_2d::{Coord, Size};
 use derive_more::{Deref, DerefMut};
@@ -59,6 +62,7 @@ impl Viewshed {
         map: &Map<D>,
         visible_query: &Query<&Visible>,
         events: &mut EventWriter<VisibilityChanged>,
+        cache: &mut HashMap<(FloatOrd, FloatOrd), (u8, HashSet<Entity>)>,
     ) {
         let mut context: Context<u8> = Context::default();
         let vision_distance = vision_distance::Circle::new(self.range);
@@ -70,11 +74,22 @@ impl Viewshed {
         let visibility_grid = VisibilityGrid(
             map,
             RefCell::new(Box::new(|coord: Coord| {
+                let dest = point!(coord.x as f32 + 0.5, coord.y as f32 + 0.5);
+                if let Some((opacity, entities)) = cache.get(&(FloatOrd(dest.x), FloatOrd(dest.y)))
+                {
+                    for e in entities {
+                        new_visible_entities.insert(*e);
+                        return *opacity;
+                    }
+                }
                 let tile = map.at(coord.x as usize, coord.y as usize);
                 if tile.blocks_visibility() {
+                    cache.insert(
+                        (FloatOrd(dest.x), FloatOrd(dest.y)),
+                        (u8::MAX, HashSet::new()),
+                    );
                     return u8::MAX;
                 }
-                let dest = point!(coord.x as f32 + 0.5, coord.y as f32 + 0.5);
                 if na::distance(&origin, &dest) > self.range as f32 {
                     return u8::MAX;
                 }
@@ -95,6 +110,10 @@ impl Viewshed {
                         if let Ok(visible) = visible_query.get(entity) {
                             opacity = **visible;
                         }
+                        cache.insert(
+                            (FloatOrd(dest.x), FloatOrd(dest.y)),
+                            (opacity, entities.clone()),
+                        );
                         true
                     },
                 );
@@ -297,6 +316,7 @@ fn update_viewshed<D: 'static + Clone + Default + Send + Sync>(
             }
         }
     }
+    let mut cache = HashMap::new();
     for entity in to_update.iter() {
         if let Ok((viewer_entity, mut viewshed, mut visible_entities, viewer_coordinates)) =
             viewers.get_mut(*entity)
@@ -311,6 +331,7 @@ fn update_viewshed<D: 'static + Clone + Default + Send + Sync>(
                     map,
                     &visible,
                     &mut changed,
+                    &mut cache,
                 );
             }
         }
@@ -327,6 +348,7 @@ fn remove_visible<D: 'static + Clone + Default + Send + Sync>(
     mut changed: EventWriter<VisibilityChanged>,
 ) {
     for removed in removed.iter() {
+        let mut cache = HashMap::new();
         for (viewer_entity, mut viewshed, mut visible_entities, start) in viewers.iter_mut() {
             if !visible_entities.contains(&removed) {
                 continue;
@@ -342,6 +364,7 @@ fn remove_visible<D: 'static + Clone + Default + Send + Sync>(
                     map,
                     &visible,
                     &mut changed,
+                    &mut cache,
                 );
             }
         }