From d73f6fda21286fee5829c149d0b7f6e1674c4b75 Mon Sep 17 00:00:00 2001
From: Theis Pieter Hollebeek <tphollebeek@gmail.com>
Date: Tue, 7 Apr 2026 14:45:14 +0200
Subject: [PATCH] dump quaternion trash

---
 simul/src/m3x3.rs  |  4 ++++
 simul/src/main.rs  |  7 +++---
 simul/src/quats.rs | 54 ++++++++++++++++++++++++++++++++++++++++++++++
 simul/src/scene.rs |  9 ++++++++
 simul/src/tri3.rs  |  5 ++++-
 simul/src/v3.rs    | 19 +++++++++++++++-
 6 files changed, 93 insertions(+), 5 deletions(-)
 create mode 100644 simul/src/quats.rs

diff --git a/simul/src/m3x3.rs b/simul/src/m3x3.rs
index 3c85fe1..d6150d3 100644
--- a/simul/src/m3x3.rs
+++ b/simul/src/m3x3.rs
@@ -13,6 +13,10 @@ impl M3x3 {
         Self([[1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 1.0]])
     }
 
+    pub fn new(v: [[f64; 3]; 3]) -> Self {
+        Self(v)
+    }
+
     pub fn from_v3_rot(rot: V3) -> Self {
         M3x3::new_rotate_x(rot.0) * M3x3::new_rotate_y(rot.1) * M3x3::new_rotate_z(rot.2)
     }
diff --git a/simul/src/main.rs b/simul/src/main.rs
index 2b0cc23..44a4b6a 100644
--- a/simul/src/main.rs
+++ b/simul/src/main.rs
@@ -6,6 +6,7 @@ use std::{collections::HashMap, f64::consts::PI, fs::File, io::BufReader};
 
 use crate::{
     m3x3::M3x3,
+    quats::RadianQuat,
     scene::{Model, Scene},
     tri2::Tri2,
     tri3::Tri3,
@@ -15,6 +16,7 @@ use crate::{
 };
 
 mod m3x3;
+mod quats;
 mod scene;
 mod tri2;
 mod tri3;
@@ -75,8 +77,7 @@ fn calculate_accel_axis_angle(axis: f64, tangent0: f64, tangent1: f64) -> f64 {
 
 impl<R: Renderer> window::App<R> for App {
     fn update(&mut self, delta_time: std::time::Duration) {
-        self.rot.0 += PI * 2.0 * delta_time.as_secs_f64() * 0.2;
-        self.rot.1 += PI * 2.0 * delta_time.as_secs_f64() * 0.2;
+        self.rot.0 += PI * 2.0 * delta_time.as_secs_f64() * 0.05;
         // self.rot.2 += PI * 2.0 * delta_time.as_secs_f64() * 0.2;
 
         self.motion_dev
@@ -104,7 +105,7 @@ impl<R: Renderer> window::App<R> for App {
         let mut cube = Model::new();
         let cube_obj = self.assets.get("assets/cube.obj").unwrap();
         cube.add_obj(&cube_obj, Color::RGB(165, 125, 165))
-            .rotate_by_m3x3(M3x3::from_v3_rot(self.rot))
+            .rotate_by_m3x3(self.dev_rot_rot)
             .scale(V3(0.4, 0.4, 0.4))
             .translate(V3(0.0, 0.0, 1.0));
         scene.draw_model(cube);
diff --git a/simul/src/quats.rs b/simul/src/quats.rs
new file mode 100644
index 0000000..4ddf968
--- /dev/null
+++ b/simul/src/quats.rs
@@ -0,0 +1,54 @@
+use crate::v3::V3;
+
+const I: V3 = V3(1.0, 0.0, 0.0);
+const J: V3 = V3(0.0, 1.0, 0.0);
+const K: V3 = V3(0.0, 0.0, 1.0);
+
+#[derive(Copy, Clone)]
+pub struct RadianQuat {
+    pub rad: f64,
+    pub u: V3,
+}
+
+#[derive(Copy, Clone)]
+pub struct Quat {
+    pub a: f64,
+    pub u: V3,
+}
+
+impl Quat {
+    fn len(&self) -> f64 {
+        (self.a.powi(2) + self.u.0.powi(2) + self.u.1.powi(2) + self.u.2.powi(2)).sqrt()
+    }
+    fn as_unit(&self) -> Quat {
+        let len = self.len();
+        Quat {
+            a: self.a / len,
+            u: self.u.map(|x| x / len),
+        }
+    }
+}
+
+impl RadianQuat {
+    pub fn as_quat(&self) -> Quat {
+        let RadianQuat { rad, u } = self.as_unit();
+        Quat {
+            a: rad.cos(),
+            u: u.map(|x| x * rad.sin()),
+        }
+    }
+    fn as_unit(&self) -> Self {
+        let len = self.u.0 + self.u.1 + self.u.2;
+        let u = self.u.map(|x| x / len);
+
+        RadianQuat { rad: self.rad, u }
+    }
+    pub fn as_inverse_quat(&self) -> Quat {
+        let RadianQuat { rad, u } = self.as_unit();
+        let u = u.map(|x| x * -1.0 * rad.sin());
+        Quat { a: -rad.cos(), u }
+    }
+    pub fn vector_quat(&self) -> V3 {
+        self.u
+    }
+}
diff --git a/simul/src/scene.rs b/simul/src/scene.rs
index 811cf77..65dfa3c 100644
--- a/simul/src/scene.rs
+++ b/simul/src/scene.rs
@@ -4,6 +4,7 @@ use obj::Obj;
 
 use crate::{
     m3x3::M3x3,
+    quats::RadianQuat,
     tri2::Tri2,
     tri3::Tri3,
     v3::V3,
@@ -108,6 +109,14 @@ impl Model {
         self
     }
 
+    pub fn rotate_by_quat(&mut self, rot: RadianQuat) -> &mut Self {
+        for tri in &mut self.tris {
+            tri.0 = tri.0.rotate_by_quat(rot);
+            tri.1 = tri.1.rotate_by_quat(rot);
+        }
+        self
+    }
+
     pub fn scale(&mut self, scale: V3) -> &mut Self {
         for tri in &mut self.tris {
             tri.0 = tri.0.scale(scale);
diff --git a/simul/src/tri3.rs b/simul/src/tri3.rs
index 4e2d4c5..0a88cf8 100644
--- a/simul/src/tri3.rs
+++ b/simul/src/tri3.rs
@@ -1,4 +1,4 @@
-use crate::{m3x3::M3x3, tri2::Tri2, v3::V3};
+use crate::{m3x3::M3x3, quats::RadianQuat, tri2::Tri2, v3::V3};
 
 #[derive(Clone, Copy, Debug)]
 pub struct Tri3(pub V3, pub V3, pub V3);
@@ -26,6 +26,9 @@ impl Tri3 {
     pub fn rotate_by_m3x3(&self, rot: M3x3) -> Self {
         self.map(|v| v.rotate_by_m3x3(rot))
     }
+    pub fn rotate_by_quat(&self, rot: RadianQuat) -> Self {
+        self.map(|v| v.rotate_by_quat(rot))
+    }
 
     pub fn project_2d(&self, camera_pos: V3, camera_rot: M3x3, screen_rel_pos: V3) -> Tri2 {
         Tri2(
diff --git a/simul/src/v3.rs b/simul/src/v3.rs
index 1f45ae5..4a93da7 100644
--- a/simul/src/v3.rs
+++ b/simul/src/v3.rs
@@ -1,4 +1,8 @@
-use crate::{m3x3::M3x3, v2::V2};
+use crate::{
+    m3x3::M3x3,
+    quats::{Quat, RadianQuat},
+    v2::V2,
+};
 use std::ops::{Add, Div, Mul, Neg, Sub};
 
 #[derive(Clone, Copy, Debug)]
@@ -44,6 +48,19 @@ impl V3 {
             * (M3x3::new_rotate_y(rot.1) * (M3x3::new_rotate_x(rot.0) * *self))
     }
 
+    pub fn rotate_by_quat(&self, rot: RadianQuat) -> Self {
+        let u = rot.vector_quat();
+        let theta = rot.rad;
+        let q_real = theta.cos();
+        let q_vector = u * theta.sin();
+        let p = *self;
+
+        let r = p
+            + (u.cross(p)) * 2.0 * theta.cos() * theta.sin()
+            + (u * 2.0 * theta.sin().powi(2)).cross(u.cross(p));
+        r
+    }
+
     pub fn rotate_by_m3x3(&self, rot: M3x3) -> Self {
         rot * *self
     }