From 94eaa60fde9982a2b9dd8fe806d5e9f8953cc91f Mon Sep 17 00:00:00 2001
From: Joe Ardent <code@ardent.nebcorp.com>
Date: Sun, 7 Sep 2025 12:21:12 -0700
Subject: [PATCH] working filled triangles

---
 src/main.rs | 47 ++++++++++++++++-------------------------------
 1 file changed, 16 insertions(+), 31 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 3403224..0f8d254 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -133,7 +133,6 @@ fn line_verts(mut a: Point2i, mut b: Point2i) -> Vec<Point2i> {
     let mut verts: Vec<Point2i> = Vec::new();
 
     let step = (b.y - a.y) as f32 / (b.x - a.x) as f32;
-    let sign = step.signum() as i32;
     let mut y = a.y as f32;
     for x in (a.x)..b.x {
         let p = if is_steep {
@@ -155,38 +154,24 @@ fn triangle_lines(a: Point2i, b: Point2i, c: Point2i, color: TGAColor, fb: &mut
 }
 
 fn triangle_filled(a: Point2i, b: Point2i, c: Point2i, color: TGAColor, fb: &mut TGAImage) {
-    let mut verts = line_verts(a, b);
-    verts.extend(line_verts(b, c));
-    verts.extend(line_verts(c, a));
+    let mut sorted = [a, b, c];
+    sorted.sort_unstable_by(|a, b| a.y.cmp(&b.y));
+    let [a, b, c] = sorted;
 
-    let mut lines: BTreeMap<i32, Vec<i32>> = BTreeMap::new();
-    for vert in verts.into_iter() {
-        lines
-            .entry(vert.y)
-            .and_modify(|e| {
-                e.push(vert.x);
-                e.sort_unstable();
-            })
-            .or_insert(vec![vert.x]);
+    let total_height = c.y - a.y;
+
+    let segment_height = b.y - a.y;
+    for y in a.y..=b.y {
+        let dy = y - a.y;
+        let x1 = a.x + ((c.x - a.x) * dy) / total_height;
+        let x2 = a.x + ((b.x - a.x) * dy) / segment_height;
+        line(Point2i::new(x1, y), Point2i::new(x2, y), color, fb);
     }
 
-    let mut prev_y: Option<i32> = None;
-    for (y, xs) in lines.iter_mut() {
-        let len = xs.len();
-        match len {
-            0 => {}
-            1 => fb.set(xs[0] as u32, *y as u32, color),
-            _ => {
-                let start = xs[0];
-                let end = xs[len - 1];
-                line(Point2i::new(start, *y), Point2i::new(end, *y), color, fb);
-            }
-        }
-        if let Some(prev) = prev_y {
-            if (y - prev).abs() > 1 {
-                dbg!(y);
-            }
-        }
-        prev_y = Some(*y)
+    let segment_height = c.y - b.y;
+    for y in b.y..=c.y {
+        let x1 = a.x + ((c.x - a.x) * (y - a.y)) / total_height;
+        let x2 = b.x + ((c.x - b.x) * (y - b.y)) / segment_height;
+        line(Point2i::new(x1, y), Point2i::new(x2, y), color, fb);
     }
 }