From 59d264a38f42f4b44da829296f8df9a6ae8c8e23 Mon Sep 17 00:00:00 2001
From: Joe Ardent <code@ardent.nebcorp.com>
Date: Sun, 7 Sep 2025 13:08:44 -0700
Subject: [PATCH] parallel lines, aabb for triangles

---
 Cargo.lock  | 52 +++++++++++++++++++++++++++++++++++++++++++++++++
 Cargo.toml  |  1 +
 src/main.rs | 56 +++++++++++++++++++++++++++++++++++++++++------------
 3 files changed, 97 insertions(+), 12 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 89132c3..b3b322b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8,6 +8,37 @@ version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2fd1289c04a9ea8cb22300a459a72a385d7c73d3259e2ed7dcb2af674838cfa9"
 
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9dd111b7b7f7d55b72c0a6ae361660ee5853c9af73f70c3c2ef6858b950e2e51"
+dependencies = [
+ "crossbeam-epoch",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5b82ac4a3c2ca9c3460964f020e1402edd5753411d7737aa39c3714ad1b5420e"
+dependencies = [
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d0a5c400df2834b80a4c3327b3aad3a4c4cd4de0629063962b03235697506a28"
+
+[[package]]
+name = "either"
+version = "1.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
+
 [[package]]
 name = "getrandom"
 version = "0.3.3"
@@ -99,6 +130,26 @@ dependencies = [
  "getrandom",
 ]
 
+[[package]]
+name = "rayon"
+version = "1.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "368f01d005bf8fd9b1206fb6fa653e6c4a81ceb1466406b81792d87c5677a58f"
+dependencies = [
+ "either",
+ "rayon-core",
+]
+
+[[package]]
+name = "rayon-core"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22e18b0f0062d30d4230b2e85ff77fdfe4326feb054b9783a3460d8435c8ab91"
+dependencies = [
+ "crossbeam-deque",
+ "crossbeam-utils",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.109"
@@ -147,6 +198,7 @@ version = "0.1.0"
 dependencies = [
  "justerror",
  "rand",
+ "rayon",
  "thiserror",
 ]
 
diff --git a/Cargo.toml b/Cargo.toml
index e86659c..43ccbe3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,4 +6,5 @@ edition = "2024"
 [dependencies]
 justerror = "1.1.0"
 rand = "0.9.2"
+rayon = "1.11.0"
 thiserror = "2.0.16"
diff --git a/src/main.rs b/src/main.rs
index fdf631e..a712b97 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,10 +1,12 @@
 #[macro_use]
 extern crate justerror;
 
-mod tga;
-use std::collections::BTreeMap;
+use std::sync::{Arc, Mutex};
 
 use rand::Rng;
+use rayon::prelude::*;
+
+mod tga;
 use tga::*;
 
 mod point;
@@ -112,7 +114,7 @@ fn _bench(fb: &mut TGAImage) {
     }
 }
 
-fn line(mut a: Point2i, mut b: Point2i, color: TGAColor, fb: &mut TGAImage) {
+fn line(mut a: Point2i, mut b: Point2i, color: TGAColor, mut fb: &mut TGAImage) {
     let is_steep = (a.x - b.x).abs() < (a.y - b.y).abs();
     if is_steep {
         std::mem::swap(&mut a.x, &mut a.y);
@@ -122,17 +124,30 @@ fn line(mut a: Point2i, mut b: Point2i, color: TGAColor, fb: &mut TGAImage) {
         std::mem::swap(&mut a, &mut b);
     }
 
+    let fb = Arc::new(Mutex::new(fb));
+    let y = Arc::new(Mutex::new(a.y as f32));
+
     let step = (b.y - a.y) as f32 / (b.x - a.x) as f32;
-    let mut y = a.y as f32;
-    for x in (a.x)..b.x {
-        let (px, py) = if is_steep {
-            (y.round_ties_even() as i32, x)
-        } else {
-            (x, y.round_ties_even() as i32)
+    (a.x..b.x).into_par_iter().for_each(|x| {
+        let ny = {
+            if let Ok(y) = y.lock() {
+                *y
+            } else {
+                return;
+            }
         };
-        fb.set(px as u32, py as u32, color);
-        y += step;
-    }
+        let (px, py) = if is_steep {
+            (ny.round_ties_even() as i32, x)
+        } else {
+            (x, ny.round_ties_even() as i32)
+        };
+        if let Ok(mut fb) = fb.lock() {
+            fb.set(px as u32, py as u32, color);
+        }
+        if let Ok(mut y) = y.lock() {
+            *y += step;
+        }
+    });
 }
 
 fn triangle_lines(a: Point2i, b: Point2i, c: Point2i, color: TGAColor, fb: &mut TGAImage) {
@@ -148,6 +163,13 @@ fn triangle_filled(a: Point2i, b: Point2i, c: Point2i, color: TGAColor, fb: &mut
 
     let total_height = c.y - a.y;
 
+    let (lower_left, upper_right) = triangle_bb(a, b, c);
+    for y in lower_left.y..=upper_right.y {
+        let a = Point2i::new(lower_left.x, y);
+        let b = Point2i::new(upper_right.x, y);
+        line(a, b, color, fb);
+    }
+
     let segment_height = b.y - a.y;
     for y in a.y..=b.y {
         let dy = y - a.y;
@@ -163,3 +185,13 @@ fn triangle_filled(a: Point2i, b: Point2i, c: Point2i, color: TGAColor, fb: &mut
         line(Point2i::new(x1, y), Point2i::new(x2, y), color, fb);
     }
 }
+
+fn triangle_bb(a: Point2i, b: Point2i, c: Point2i) -> (Point2i, Point2i) {
+    let xmax = a.x.max(b.x.max(c.x));
+    let xmin = a.x.min(b.x.min(c.x));
+
+    let ymax = a.y.max(b.y.max(c.y));
+    let ymin = a.y.min(b.y.min(c.y));
+
+    (Point2i::new(xmin, ymin), Point2i::new(xmax, ymax))
+}