From 24886c2752548f1c32ed54968a7bfdf2b1fe38ea Mon Sep 17 00:00:00 2001
From: Kai Stevenson <kai@kaistevenson.com>
Date: Sun, 16 Aug 2026 00:46:57 -0700
Subject: fire changes + smoke

---
 src/sim/materials/fire.rs | 46 +++++++++++++++++++++++++++++++++++-----------
 1 file changed, 35 insertions(+), 11 deletions(-)

(limited to 'src/sim/materials/fire.rs')

diff --git a/src/sim/materials/fire.rs b/src/sim/materials/fire.rs
index b155986..3c686fe 100644
--- a/src/sim/materials/fire.rs
+++ b/src/sim/materials/fire.rs
@@ -21,25 +21,28 @@ impl FireCellView for Cell {
     }
 }
 
+// TODO optimize number of rng calls?
 #[inline]
 pub fn sim_update(ctx: &mut UpdateCtx) {
     let ticks_lived = ctx.cell.get_ticks_lived();
     // 2 seconds
     if ticks_lived > 240 {
-        // kill ourselves, with a chance to turn into ash
-        if ctx.rng.random_range(0.0..1.0) > 0.8 {
-            // TODO ash material
-            ctx.set_cell(0, 0, Cell::from_material(MaterialId::Sand));
-        } else {
-            ctx.set_cell(0, 0, Cell::void());
+        // we have a chance to live longer--roughly 50% chance of living an extra second
+        if ctx.rng.random_range(0.0..1.0) > 0.995 {
+            // kill ourselves, with a chance to turn into ash
+            if ctx.rng.random_range(0.0..1.0) > 0.8 {
+                // TODO ash material
+                ctx.set_cell(0, 0, Cell::from_material(MaterialId::Sand));
+            } else {
+                ctx.set_cell(0, 0, Cell::void());
+            }
+            return;
         }
-        return;
     }
 
-    // 4 times in our lifespan, try to spread in a random direction
-    // since it's random, fire may die out if there's nothing in that direction
-    // a 1-thick line of flammable cells has a 31% chance to die each iteration
-    if ticks_lived % 60 == 0 {
+    // at an average of 4 times per lifespan, try to spread
+    // 1/60 * 240 = 4
+    if ctx.rng.random_range(0.0..1.0) > (59.0 / 60.0) {
         let (dx, dy) = (ctx.rng.random_range(-1..=1), ctx.rng.random_range(-1..=1));
         if let Some(target) = ctx.get_cell(dx, dy)
             && target.is_flammable()
@@ -48,6 +51,27 @@ pub fn sim_update(ctx: &mut UpdateCtx) {
         }
     }
 
+    // 8 times in our lifespan, emit smoke
+    if ticks_lived % 30 == 0 {
+        if let Some(target) = ctx.get_cell(0, -1)
+            && target.material == MaterialId::Void
+        {
+            for (dx, dy) in [
+                (0, -1),
+                (1 - ctx.seqno_parity as i32 * 2, 0),
+                (-1 + ctx.seqno_parity as i32 * 2, 0),
+                (0, 1),
+            ] {
+                if let Some(target) = ctx.get_cell(dx, dy)
+                    && target.material == MaterialId::Void
+                {
+                    ctx.set_cell(dx, dy, Cell::from_material(MaterialId::Smoke));
+                    break;
+                }
+            }
+        }
+    }
+
     ctx.cell.set_ticks_lived(ticks_lived + 1);
     ctx.set_cell(0, 0, *ctx.cell);
 }
-- 
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