From 8201c8e2a7ff85383ff7606513778253aae7e666 Mon Sep 17 00:00:00 2001
From: Sakarias Johansson <sakarias.johansson@goodbyekansas.com>
Date: Fri, 14 Apr 2023 20:58:23 +0200
Subject: =?UTF-8?q?=E2=9C=A8=20Add=20support=20for=20camera=20rotation?=
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Before you could only move the position of the camera.

- Add support for turning camera by holding down left mouse.
- Add support for turning camera with arrow keys.
- Add Mouse move callback for key_inputs.
---
 racer-tracer/src/camera.rs | 55 +++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 49 insertions(+), 6 deletions(-)

(limited to 'racer-tracer/src/camera.rs')

diff --git a/racer-tracer/src/camera.rs b/racer-tracer/src/camera.rs
index e6396e8..1ac2396 100644
--- a/racer-tracer/src/camera.rs
+++ b/racer-tracer/src/camera.rs
@@ -1,3 +1,5 @@
+use glam::{f32::Vec3 as FVec3, Quat};
+
 use crate::image::Image;
 use crate::ray::Ray;
 use crate::util::{degrees_to_radians, random_in_unit_disk};
@@ -14,6 +16,7 @@ pub struct Camera {
     pub forward: Vec3,
     pub right: Vec3,
     pub up: Vec3,
+    pub scene_up: Vec3,
     pub lens_radius: f64,
     pub focus_distance: f64,
 }
@@ -22,7 +25,7 @@ impl Camera {
     pub fn new(
         look_from: Vec3,
         look_at: Vec3,
-        up: Vec3,
+        scene_up: Vec3,
         vfov: f64,
         image: &Image,
         aperture: f64,
@@ -33,7 +36,7 @@ impl Camera {
         let viewport_width = image.aspect_ratio * viewport_height;
 
         let forward = (look_from - look_at).unit_vector();
-        let right = up.cross(&forward).unit_vector();
+        let right = scene_up.cross(&forward).unit_vector();
         let up = forward.cross(&right);
 
         let horizontal = focus_distance * viewport_width * right;
@@ -50,6 +53,7 @@ impl Camera {
             forward,
             right,
             up,
+            scene_up,
             lens_radius: aperture * 0.5,
             focus_distance,
         }
@@ -66,17 +70,56 @@ impl Camera {
 
     pub fn go_forward(&mut self, go: f64) {
         self.origin += self.forward * go;
-
-        self.upper_left_corner = self.origin + self.vertical / 2.0
-            - self.horizontal / 2.0
-            - self.focus_distance * self.forward;
+        self.update_corner()
     }
 
     pub fn go_right(&mut self, go: f64) {
         self.origin += self.right * go;
+        self.update_corner()
+    }
 
+    fn update_corner(&mut self) {
         self.upper_left_corner = self.origin + self.vertical / 2.0
             - self.horizontal / 2.0
             - self.focus_distance * self.forward;
     }
+
+    fn update_directions(&mut self) {
+        self.forward.unit_vector();
+        self.right = self.scene_up.cross(&self.forward).unit_vector();
+        self.up = self.forward.cross(&self.right);
+        self.horizontal = self.focus_distance * self.viewport_width * self.right;
+        self.vertical = self.focus_distance * self.viewport_height * self.up;
+    }
+
+    pub fn rotate(&mut self, up: f64, right: f64) {
+        self.forward = (Quat::from_axis_angle(self.right.into(), right as f32)
+            * Quat::from_axis_angle(self.scene_up.into(), up as f32)
+            * FVec3::from(self.forward))
+        .into();
+
+        self.forward.unit_vector();
+        self.update_directions();
+        self.update_corner();
+    }
+
+    pub fn rotate_up(&mut self, go: f64) {
+        self.forward = (Quat::from_axis_angle(self.right.into(), go as f32)
+            * FVec3::from(self.forward))
+        .into();
+
+        self.forward.unit_vector();
+        self.update_directions();
+        self.update_corner();
+    }
+
+    pub fn rotate_right(&mut self, go: f64) {
+        self.forward = (Quat::from_axis_angle(self.scene_up.into(), -go as f32)
+            * FVec3::from(self.forward))
+        .into();
+
+        self.forward.unit_vector();
+        self.update_directions();
+        self.update_corner();
+    }
 }
-- 
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