magical transform functions

src/camera.rs

@@ -1,4 +1,6 @@
-use glam::{Vec3, vec3};
+use std::f32::consts::PI;
+
+use glam::{Mat4, Vec3, vec3};
 
 /// A camera always directed at the origin.
 #[derive(Debug, Clone, Copy)]
@@ -19,24 +21,38 @@ impl OrbitalCamera {
 		let (z, xy) = self.position_pitch.sin_cos();
 		self.distance * vec3(xy * x, xy * y, z)
 	}
+
+	pub fn transform(&self) -> Mat4 {
+		Mat4::from_translation(vec3(0., 0., self.distance))
+			* Mat4::from_euler(glam::EulerRot::ZXZ, 0., PI / 2., -PI / 2.)
+			* Mat4::from_euler(
+				glam::EulerRot::ZYZ,
+				0.,
+				self.position_pitch,
+				-self.position_yaw,
+			)
+	}
 }
 
 #[cfg(test)]
 mod tests {
-	use approx::assert_ulps_eq;
+	use approx::{abs_diff_eq, assert_ulps_eq};
 	use glam::vec3;
 
 	use super::*;
 
+	fn camera_deg(yaw: f32, pitch: f32) -> OrbitalCamera {
+		OrbitalCamera {
+			position_yaw: yaw.to_radians(),
+			position_pitch: pitch.to_radians(),
+			distance: 1.0,
+		}
+	}
+
 	#[test]
 	fn test_orbital_camera_position() {
 		fn camera_pos_deg(yaw: f32, pitch: f32) -> Vec3 {
-			OrbitalCamera {
-				position_yaw: yaw.to_radians(),
-				position_pitch: pitch.to_radians(),
-				distance: 1.0,
-			}
-			.position()
+			camera_deg(yaw, pitch).position()
 		}
 		assert_ulps_eq!(camera_pos_deg(0., 0.), vec3(1., 0., 0.), max_ulps = 3);
 		assert_ulps_eq!(camera_pos_deg(90., 0.), vec3(0., 1., 0.), max_ulps = 3);
@@ -48,4 +64,34 @@ mod tests {
 		assert_ulps_eq!(camera_pos_deg(0., 45.), vec3(s2, 0., s2), max_ulps = 3);
 		assert_ulps_eq!(camera_pos_deg(45., 45.), vec3(0.5, 0.5, s2), max_ulps = 3);
 	}
+
+	#[test]
+	fn test_orbital_camera_forward() {
+		const EPSILON: f32 = 1e-5;
+		for pitch in [0., 30., 45., 89., 90.] {
+			for yaw in [0., 30., 45., 89., 90.] {
+				let camera = camera_deg(yaw, pitch);
+				let pos = camera.position();
+				let tfm = camera.transform();
+
+				let mapped = tfm.transform_vector3(-pos);
+				assert!(
+					abs_diff_eq!(mapped, vec3(0., 0., 1.), epsilon = EPSILON),
+					"direction not mapped to +Z: yaw={yaw:?}°, pitch={pitch:?}°, pos={pos:?}, mapped={mapped:?}"
+				);
+
+				let mapped = tfm.transform_point3(pos);
+				assert!(
+					abs_diff_eq!(mapped, Vec3::ZERO, epsilon = EPSILON),
+					"pos not mapped to origin: yaw={yaw:?}°, pitch={pitch:?}°, pos={pos:?}, mapped={mapped:?}"
+				);
+
+				let mapped = tfm.transform_point3(Vec3::ZERO);
+				assert!(
+					abs_diff_eq!(mapped, vec3(0., 0., 1.), epsilon = EPSILON),
+					"origin not mapped to (0, 0, 1): yaw={yaw:?}°, pitch={pitch:?}°, pos={pos:?}, mapped={mapped:?}"
+				);
+			}
+		}
+	}
 }