From 6c56a31726ab47c78557549789117b6d42300b63 Mon Sep 17 00:00:00 2001
From: numzero <numzer0@yandex.ru>
Date: Tue, 26 Mar 2024 00:42:22 +0300
Subject: [PATCH] Use ray tracing

---
 src/main.rs | 43 ++++++++++++++++++++++++++++++++++---------
 1 file changed, 34 insertions(+), 9 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index b228c1e..e0a40d3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,8 +6,7 @@ use std::f32::consts::PI;
 use std::io::{BufRead, BufReader, BufWriter};
 use std::io::Write;
 use rand::Rng;
-use glm;
-use glm::{dot, ivec2, IVec2, ivec3, to_ivec3, vec2, Vec2, Vec3};
+use glm::*;
 use crate::mesh_loader::load_mesh;
 
 const W: i32 = 800;
@@ -106,13 +105,34 @@ fn main() -> io::Result<()> {
 		1.0, 0.0, 0.0,
 		0.0, pitch.cos(), -pitch.sin(),
 		0.0, pitch.sin(), pitch.cos());
-	let m_camera = m_roll * m_pitch * m_yaw;
-	for f in mesh {
-		let vs = f.vertices
-			.map(|v| m_camera * v)
-			.map(|v| vec2(W as f32 * 0.5 + v.x * SCALE, H as f32 * 0.5 + v.y * SCALE));
-		let color = glm::clamp(to_ivec3(f.normal * 120.0 + 128.0), ivec3(0, 0, 0), ivec3(255, 255, 255));
-		img.draw_tri(vs[0], vs[1], vs[2], Color(color.x as u8, color.y as u8, color.z as u8));
+	let m_view = m_roll * m_pitch * m_yaw;
+	let m_camera = transpose(&m_view);
+	let img_size = vec2(W as f32, H as f32);
+	for y in 0..H {
+		for x in 0..W {
+			let img_coords: Vec2 = vec2(x as f32, y as f32);
+
+			// perspective projection
+			let off = (img_coords - img_size * 0.5) / (img_size.y * 0.5);
+			let base = vec3(0.0, 0.0, -10.0);
+			let ray = vec3(off.x, off.y, 1.0);
+
+			// orthographic projection
+			let off = (img_coords - img_size * 0.5) / SCALE;
+			let base = vec3(off.x, off.y, -10.0);
+			let ray = vec3(0.0, 0.0, 1.0);
+
+			let base = m_camera * base;
+			let ray = m_camera * normalize(ray);
+
+			for f in &mesh {
+				let color = glm::clamp(to_ivec3(f.normal * 120.0 + 128.0), ivec3(0, 0, 0), ivec3(255, 255, 255));
+				let ds = (0..3).map(|k| edge_dist(f.vertices[k], f.vertices[(k + 1) % 3], base, ray));
+				if ds.into_iter().all(|d| d > 0.0) {
+					img.put_pixel(x, y, Color(color.x as u8, color.y as u8, color.z as u8));
+				}
+			}
+		}
 	}
 	let f = File::create("1.ppm")?;
 	let mut f = BufWriter::new(f);
@@ -121,3 +141,8 @@ fn main() -> io::Result<()> {
 	f.write(img.data());
 	Ok(())
 }
+
+fn edge_dist(a: Vec3, b: Vec3, base: Vec3, dir: Vec3) -> f32 {
+	let edge = normalize(b - a);
+	dot(edge, cross(base - a, base + dir - a))
+}