From 88a406f84d49dd064647c38e7bf2bda3e92a38cb Mon Sep 17 00:00:00 2001
From: Joe Ardent <code@ardent.nebcorp.com>
Date: Sun, 7 Sep 2025 13:52:14 -0700
Subject: [PATCH] move triangle methods onto Triangle struct

---
 src/main.rs | 118 ++++++++++++++++++++++++++++++++--------------------
 1 file changed, 74 insertions(+), 44 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index a712b97..c2f2eae 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -44,26 +44,23 @@ fn main() {
 }
 
 fn fill_triangles(fb: &mut TGAImage) {
-    /*
-    triangle(  7, 45, 35, 100, 45,  60, framebuffer, red);
-    triangle(120, 35, 90,   5, 45, 110, framebuffer, white);
-    triangle(115, 83, 80,  90, 85, 120, framebuffer, green);
-    */
-
     let t1a = Point2i::new(7, 45);
     let t1b = Point2i::new(35, 100);
     let t1c = Point2i::new(45, 60);
-    triangle_filled(t1a, t1b, t1c, RED, fb);
+    let t1 = Triangle::new(t1a, t1b, t1c);
+    t1.render_filled(RED, fb);
 
     let t2a = Point2i::new(120, 35);
     let t2b = Point2i::new(90, 5);
     let t2c = Point2i::new(45, 110);
-    triangle_filled(t2a, t2b, t2c, WHITE, fb);
+    let t2 = Triangle::new(t2a, t2b, t2c);
+    t2.render_filled(WHITE, fb);
 
     let a = Point2i::new(115, 83);
     let b = Point2i::new(80, 90);
     let c = Point2i::new(85, 120);
-    triangle_filled(a, b, c, GREEN, fb);
+    let t3 = Triangle::new(a, b, c);
+    t3.render_filled(GREEN, fb);
 }
 
 fn _render_diablo(model: Model, fb: &mut TGAImage) {
@@ -150,48 +147,81 @@ fn line(mut a: Point2i, mut b: Point2i, color: TGAColor, mut fb: &mut TGAImage)
     });
 }
 
-fn triangle_lines(a: Point2i, b: Point2i, c: Point2i, color: TGAColor, fb: &mut TGAImage) {
-    line(a, b, color, fb);
-    line(b, c, color, fb);
-    line(c, a, color, fb);
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+struct Triangle {
+    a: Point2i,
+    b: Point2i,
+    c: Point2i,
 }
 
-fn triangle_filled(a: Point2i, b: Point2i, c: Point2i, color: TGAColor, fb: &mut TGAImage) {
-    let mut sorted = [a, b, c];
-    sorted.sort_unstable_by(|a, b| a.y.cmp(&b.y));
-    let [a, b, c] = sorted;
-
-    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);
+impl Triangle {
+    pub fn new(a: Point2i, b: Point2i, c: Point2i) -> Self {
+        let mut sorted = [a, b, c];
+        sorted.sort_unstable_by(|a, b| a.y.cmp(&b.y));
+        let [a, b, c] = sorted;
+        Self { a, b, c }
     }
 
-    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);
+    pub fn signed_area(&self) -> f32 {
+        0.5 * ((self.b.y - self.a.y) * (self.a.x + self.b.x)
+            + (self.c.y - self.b.y) * (self.c.x + self.b.x)
+            + (self.a.y - self.c.y) * (self.a.x + self.c.x)) as f32
     }
 
-    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);
+    pub fn bb(&self) -> AABB {
+        let xmax = self.a.x.max(self.b.x.max(self.c.x));
+        let xmin = self.a.x.min(self.b.x.min(self.c.x));
+
+        let ymax = self.a.y.max(self.b.y.max(self.c.y));
+        let ymin = self.a.y.min(self.b.y.min(self.c.y));
+        AABB {
+            lower_left: Point2i::new(xmin, ymin),
+            upper_right: Point2i::new(xmax, ymax),
+        }
+    }
+    pub fn render_filled(&self, color: TGAColor, fb: &mut TGAImage) {
+        let bb = self.bb();
+        for y in bb.ymin()..=bb.ymax() {
+            let a = Point2i::new(bb.xmin(), y);
+            let b = Point2i::new(bb.xmax(), y);
+            line(a, b, color, fb);
+        }
+    }
+
+    pub fn render_lines(&self, color: TGAColor, fb: &mut TGAImage) {
+        line(self.a, self.b, color, fb);
+        line(self.b, self.c, color, fb);
+        line(self.c, self.a, 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))
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+struct AABB {
+    lower_left: Point2i,
+    upper_right: Point2i,
+}
+
+impl AABB {
+    pub fn new(lower_left: Point2i, upper_right: Point2i) -> Self {
+        Self {
+            lower_left,
+            upper_right,
+        }
+    }
+
+    pub fn xmin(&self) -> i32 {
+        self.lower_left.x
+    }
+
+    pub fn xmax(&self) -> i32 {
+        self.upper_right.x
+    }
+
+    pub fn ymin(&self) -> i32 {
+        self.lower_left.y
+    }
+
+    pub fn ymax(&self) -> i32 {
+        self.upper_right.y
+    }
 }