From e28f8b4ef5c0744912afd49d8d1ba9a94e144613 Mon Sep 17 00:00:00 2001
From: Kai Stevenson <kai@kaistevenson.com>
Date: Mon, 24 Aug 2026 20:15:21 -0700
Subject: fixes for small entities

---
 src/sim/sim_manager/mod.rs | 49 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 46 insertions(+), 3 deletions(-)

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

diff --git a/src/sim/sim_manager/mod.rs b/src/sim/sim_manager/mod.rs
index b2441ef..9ae66be 100644
--- a/src/sim/sim_manager/mod.rs
+++ b/src/sim/sim_manager/mod.rs
@@ -1,6 +1,7 @@
 use std::time::Instant;
 
 use fxhash::FxHashMap;
+use glam::Vec2;
 use rand::random_range;
 
 use crate::{
@@ -11,7 +12,7 @@ use crate::{
         cell::Cell,
         cell_manager::manager::CellManager,
         entity::{Entity, EntityDef, EntityId},
-        particle_manager::ParticleManager,
+        particle_manager::{ParticleManager, particle::Particle},
         rb_manager::RbManager,
         sim_manager::utils::{
             process_entity_update_result, read_back_entities_from_world, write_entities_to_world,
@@ -97,9 +98,41 @@ impl SimManager {
         }
     }
 
+    pub fn atomize_entity(&mut self, id: EntityId) {
+        if let Some(entity) = self.entities.get(&id)
+            && let Some(cells) = &entity.data.cells
+        {
+            // TODO these unwraps exist because we don't have separate entity position from rb
+            let rb = self
+                .rb_manager
+                .physics_manager
+                .world
+                .bodies
+                .get(entity.data.rb_h.unwrap())
+                .unwrap();
+
+            for x in 0..cells.size.x {
+                for y in 0..cells.size.y {
+                    let r = rb.position().transform_vector(
+                        Vec2::new(x as f32, y as f32) - (cells.size / 2).as_vec2(),
+                    );
+                    self.particle_manager.particles.push(Particle::new(
+                        rb.translation() + r,
+                        rb.linvel(),
+                        cells.cells[(x + y * cells.size.x) as usize].material,
+                        3.0,
+                        0.1,
+                    ))
+                }
+            }
+
+            self.destroy_entity(id);
+        }
+    }
+
     fn cell_update(&mut self, config: &Config, input_manager: &InputManager, delta_time: f32) {
         // before we tick, write all the entities into the sim world
-        let cells_written_by_entity = write_entities_to_world(self);
+        let written_entities_scope = write_entities_to_world(self);
 
         // --TEST DRAWING--
         if input_manager.lmb_held || input_manager.rmb_held {
@@ -136,6 +169,16 @@ impl SimManager {
             }
         }
 
+        if input_manager.pressed(Input::Action2) {
+            if let Some(entity_id) = written_entities_scope
+                .get_entity_id_at_position(input_manager.world_mouse_pos.round().as_ivec2())
+            {
+                self.atomize_entity(entity_id);
+            }
+        }
+
+        // TEST ATOMIZATION
+
         // tick
         self.cell_manager.tick(config.use_threading);
 
@@ -157,7 +200,7 @@ impl SimManager {
         }
 
         // after we tick, remove the written entity cells and update the entities
-        read_back_entities_from_world(self, cells_written_by_entity);
+        read_back_entities_from_world(self, written_entities_scope);
     }
 
     fn physics_update(&mut self, input_manager: &InputManager, delta_time: f32) {
-- 
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