From 1a515237afb7ad09353a65f5fbc6e98a7c29ce8e Mon Sep 17 00:00:00 2001
From: Kai Stevenson <kai@kaistevenson.com>
Date: Sat, 22 Aug 2026 15:00:35 -0700
Subject: sim manager refactor

---
 src/sim/sim_manager/utils.rs | 62 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 src/sim/sim_manager/utils.rs

(limited to 'src/sim/sim_manager/utils.rs')

diff --git a/src/sim/sim_manager/utils.rs b/src/sim/sim_manager/utils.rs
new file mode 100644
index 0000000..b636186
--- /dev/null
+++ b/src/sim/sim_manager/utils.rs
@@ -0,0 +1,62 @@
+use crate::sim::{cell::materials::MaterialId, sim_manager::SimManager};
+
+pub fn write_rb_entity_to_world(
+    sim: &mut SimManager,
+    rb_entity_id: u32,
+    // make sure these cells will be simulated
+    seqno: u64,
+    // (entity_x, entity_y, cell_x, cell_y)
+) -> Vec<(u8, u8, i32, i32)> {
+    let mut cells_written: Vec<(u8, u8, i32, i32)> = Vec::new();
+    if let Some(rb_entity) = sim.rb_manager.rb_entities.get(&rb_entity_id)
+        && let Some((rb_x, rb_y, cos, sin)) = sim.rb_manager.get_rb_entity_transform(rb_entity_id)
+    {
+        let (half_size_x, half_size_y) =
+            (rb_entity.width as f32 / 2.0, rb_entity.height as f32 / 2.0);
+        // half-extent of the rotated grid's axis-aligned bounding box, plus a cell of margin
+        let (radius_x, radius_y) = (
+            half_size_x * (cos.abs() + sin.abs()) + 1.0,
+            half_size_y * (cos.abs() + sin.abs()) + 1.0,
+        );
+
+        let world_xl = (rb_x - radius_x).floor() as i32;
+        let world_xu = (rb_x + radius_x).ceil() as i32;
+        let world_yl = (rb_y - radius_y).floor() as i32;
+        let world_yu = (rb_y + radius_y).ceil() as i32;
+
+        for world_x in world_xl..=world_xu {
+            for world_y in world_yl..=world_yu {
+                if let Some(cur_world_cell) = sim
+                    .cell_manager
+                    .get_cell_from_game_position(world_x, world_y)
+                    && cur_world_cell.material == MaterialId::Void
+                {
+                    // same as shader
+                    let d = (world_x as f32 + 0.5 - rb_x, world_y as f32 + 0.5 - rb_y);
+                    let q = (d.0.floor() + 0.5, d.1.floor() + 0.5);
+                    let (lx, ly) = (
+                        (q.0 * cos + q.1 * sin + half_size_x).floor() as i32,
+                        (-q.0 * sin + q.1 * cos + half_size_y).floor() as i32,
+                    );
+
+                    if lx < 0 || ly < 0 || lx >= rb_entity.width || ly >= rb_entity.height {
+                        continue;
+                    }
+
+                    let mut cell = rb_entity.get_cell_at_local_position(lx as u8, ly as u8);
+                    if cell.material == MaterialId::Void {
+                        continue;
+                    }
+
+                    cell.match_parity(seqno);
+
+                    // TODO: OPTIMIZE!!
+                    sim.cell_manager
+                        .set_cell_from_game_position(world_x, world_y, cell, false);
+                    cells_written.push((lx as u8, ly as u8, world_x, world_y));
+                }
+            }
+        }
+    }
+    cells_written
+}
-- 
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