From feefeecec6c6050635b2c016452dfa1529575987 Mon Sep 17 00:00:00 2001
From: Kai Stevenson <kai@kaistevenson.com>
Date: Thu, 13 Aug 2026 01:56:09 -0700
Subject: big refactor for board

---
 src/camera.rs | 110 ++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 77 insertions(+), 33 deletions(-)

(limited to 'src/camera.rs')

diff --git a/src/camera.rs b/src/camera.rs
index 604cb0d..9310cac 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -1,7 +1,7 @@
 use crate::{
     Input,
-    config::{CAMERA_MOVEMENT_SPEED, PIXEL_BUFFER_HEIGHT, PIXEL_BUFFER_WIDTH},
-    sim::board::Board,
+    config::{CAMERA_MOVEMENT_SPEED, CHUNK_SIZE, PIXEL_BUFFER_HEIGHT, PIXEL_BUFFER_WIDTH},
+    sim::{chunk::Chunk, world::World},
 };
 
 pub struct Camera {
@@ -42,14 +42,9 @@ impl Camera {
         self.y += adjusted_y as f64;
     }
 
-    pub fn screen_position_to_board(
-        &self,
-        board: &Board,
-        screen_x: f64,
-        screen_y: f64,
-    ) -> (f64, f64) {
-        let camera_width = self.zoom * f64::from(board.size_x);
-        let camera_height = self.zoom * f64::from(board.size_y);
+    pub fn screen_position_to_world(&self, screen_x: f64, screen_y: f64) -> (f64, f64) {
+        let camera_width = self.zoom * f64::from(PIXEL_BUFFER_WIDTH);
+        let camera_height = self.zoom * f64::from(PIXEL_BUFFER_HEIGHT);
         let camera_start_x = self.x - camera_width / 2.0;
         let camera_start_y = self.y - camera_height / 2.0;
         (
@@ -58,32 +53,81 @@ impl Camera {
         )
     }
 
-    pub fn write_frame_view(
+    pub fn write_frame_view(&self, frame: &mut [u8], world: &World) {
+        puffin::profile_function!();
+
+        const BG: [u8; 4] = [0x00, 0x00, 0x00, 0xFF];
+        for px in frame.chunks_exact_mut(4) {
+            px.copy_from_slice(&BG);
+        }
+
+        // world-space rect covered by the screen
+        let (xl, yl) = self.screen_position_to_world(0.0, 0.0);
+        let (xu, yu) =
+            self.screen_position_to_world(PIXEL_BUFFER_WIDTH as f64, PIXEL_BUFFER_HEIGHT as f64);
+
+        let c = CHUNK_SIZE as i32;
+        let cx0 = (xl.floor() as i32).div_euclid(c);
+        let cx1 = (xu.ceil() as i32).div_euclid(c);
+        let cy0 = (yl.floor() as i32).div_euclid(c);
+        let cy1 = (yu.ceil() as i32).div_euclid(c);
+
+        let scale = 1.0 / self.zoom; // pixels per cell
+
+        for cy in cy0..=cy1 {
+            for cx in cx0..=cx1 {
+                let Some(&idx) = world.chunk_position_to_chunk_idx.get(&(cx, cy)) else {
+                    continue;
+                };
+                self.write_chunk(frame, &world.chunks[idx], cx, cy, xl, yl, scale);
+            }
+        }
+    }
+
+    fn write_chunk(
         &self,
         frame: &mut [u8],
-        board: &Board,
-        get_overlay: impl Fn(i32, i32) -> (u8, u8, u8, u8),
+        chunk: &Chunk,
+        cx: i32,
+        cy: i32,
+        xl: f64,
+        yl: f64,
+        scale: f64,
     ) {
-        for frame_y in 0..PIXEL_BUFFER_HEIGHT {
-            for frame_x in 0..PIXEL_BUFFER_WIDTH {
-                let (x_coord, y_coord) =
-                    self.screen_position_to_board(board, frame_x as f64, frame_y as f64);
-
-                let cell = board.cell_at_position(x_coord as i32, y_coord as i32);
-                let cell_color: Option<(u8, u8, u8, u8)> = cell.map(|c| {
-                    let m = c.material.def();
-                    (m.color[0], m.color[1], m.color[2], 0xFF)
-                });
-                let off_grid_color: (u8, u8, u8, u8) = (0x00, 0x00, 0x00, 0xFF);
-
-                let target_color: (u8, u8, u8, u8) = cell_color.unwrap_or(off_grid_color);
-                let overlay = get_overlay(x_coord as i32, y_coord as i32);
-
-                let frame_idx = ((frame_y * PIXEL_BUFFER_WIDTH + frame_x) * 4) as usize;
-                frame[frame_idx] = target_color.0.saturating_add(overlay.0);
-                frame[frame_idx + 1] = target_color.1.saturating_add(overlay.1);
-                frame[frame_idx + 2] = target_color.2.saturating_add(overlay.2);
-                frame[frame_idx + 3] = target_color.3.saturating_add(overlay.3);
+        let c = CHUNK_SIZE as i32;
+        let w = PIXEL_BUFFER_WIDTH as i32;
+        let h = PIXEL_BUFFER_HEIGHT as i32;
+
+        for ly in 0..c {
+            let wy = (cy * c + ly) as f64;
+            let sy0 = (((wy - yl) * scale).floor() as i32).max(0);
+            let sy1 = (((wy + 1.0 - yl) * scale).floor() as i32).min(h);
+            if sy0 >= sy1 {
+                continue;
+            }
+
+            for lx in 0..c {
+                let wx = (cx * c + lx) as f64;
+                let sx0 = (((wx - xl) * scale).floor() as i32).max(0);
+                let sx1 = (((wx + 1.0 - xl) * scale).floor() as i32).min(w);
+                if sx0 >= sx1 {
+                    continue;
+                }
+
+                let color = chunk
+                    .get_cell_at_local_position(lx as u8, ly as u8)
+                    .material
+                    .def()
+                    .color;
+                let rgba = [color.0, color.1, color.2, color.3];
+
+                for sy in sy0..sy1 {
+                    let start = (sy * w + sx0) as usize * 4;
+                    let end = (sy * w + sx1) as usize * 4;
+                    for px in frame[start..end].chunks_exact_mut(4) {
+                        px.copy_from_slice(&rgba);
+                    }
+                }
             }
         }
     }
-- 
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