From d7eccba2055cd7784a0db6d9ee8692a4f3510931 Mon Sep 17 00:00:00 2001
From: Kai Stevenson <kai@kaistevenson.com>
Date: Sat, 15 Aug 2026 22:46:53 -0700
Subject: fire, optimize viewport rendering

---
 src/sim/materials/fire.rs | 53 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 src/sim/materials/fire.rs

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

diff --git a/src/sim/materials/fire.rs b/src/sim/materials/fire.rs
new file mode 100644
index 0000000..b155986
--- /dev/null
+++ b/src/sim/materials/fire.rs
@@ -0,0 +1,53 @@
+use rand::RngExt;
+
+use crate::sim::{cell::Cell, materials::MaterialId, sim::UpdateCtx};
+
+trait FireCellView {
+    fn get_ticks_lived(self) -> u16;
+    fn set_ticks_lived(&mut self, ticks: u16) -> ();
+    fn is_flammable(self) -> bool;
+}
+
+impl FireCellView for Cell {
+    fn get_ticks_lived(self) -> u16 {
+        self.data
+    }
+    fn set_ticks_lived(&mut self, ticks: u16) -> () {
+        self.data = ticks;
+    }
+    // this could be a property of the material def, I think it's better here for now
+    fn is_flammable(self) -> bool {
+        [MaterialId::Wood].contains(&self.material)
+    }
+}
+
+#[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());
+        }
+        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 {
+        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()
+        {
+            ctx.set_cell(dx, dy, Cell::from_material(MaterialId::Fire));
+        }
+    }
+
+    ctx.cell.set_ticks_lived(ticks_lived + 1);
+    ctx.set_cell(0, 0, *ctx.cell);
+}
-- 
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