From 8c0ae03addfdda9105728443fa32af7f7081f6c7 Mon Sep 17 00:00:00 2001
From: numzero <numzer0@yandex.ru>
Date: Sun, 18 Oct 2026 02:35:05 +0300
Subject: [PATCH] unify perspective/orthogonal cameras

---
 src/camera.rs         | 62 +++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs            | 17 ++++++++----
 ui/src/main_window.ui |  2 +-
 3 files changed, 75 insertions(+), 6 deletions(-)

diff --git a/src/camera.rs b/src/camera.rs
index 4d3311c..cda1641 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -16,6 +16,39 @@ pub(crate) fn projection(fovy: f32, aspect: f32, base_distance: f32) -> Mat4 {
 	Mat4::perspective_rh(fovy, aspect, 0.1 * base_distance, 10.0 * base_distance)
 }
 
+pub(crate) struct Camera {
+	pub y_frac: f32,
+	pub y_angle: f32,
+	pub y_range: f32,
+	pub z_min: f32,
+	pub z_max: f32,
+}
+
+impl Camera {
+	pub fn clamp_z_min(&mut self, min_z: f32) -> &mut Self {
+		let (s, c) = (0.5 * self.y_angle).sin_cos();
+		// let distance = 0.5 * self.y_len * c / s;
+		let distance_scaled = 0.5 * self.y_range * c;
+		if distance_scaled + self.z_min * s < min_z * s {
+			self.z_min = min_z - distance_scaled / s;
+		}
+		self
+	}
+
+	pub fn to_mat4(&self) -> Mat4 {
+		let tan_fov = (0.5 * self.y_angle).tan();
+		let z_range = self.z_max - self.z_min;
+		let y_far = 0.5 * self.y_range + self.z_max * tan_fov;
+		let u = -y_far / z_range;
+		Mat4::from_cols_array_2d(&[
+			[self.y_frac, 0., 0., 0.],
+			[0., 1., 0., 0.],
+			[0., 0., u, -tan_fov],
+			[0., 0., u * self.z_min, 0.5 * self.y_range],
+		])
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;
@@ -76,4 +109,33 @@ mod tests {
 			panic!();
 		}
 	}
+
+	#[test]
+	fn test_proj() {
+		for (y_range, y_angle_deg) in [
+			(10.000000, 53.130102f32),
+			(11.547005, 60.000000f32),
+			(20.000000, 90.000000f32),
+			(34.641016, 120.000000f32),
+			(40.000000, 126.869898f32),
+		] {
+			let y_angle = y_angle_deg.to_radians();
+			let camera = Camera {
+				y_frac: 0.5,
+				y_angle,
+				y_range,
+				z_min: -9.0,
+				z_max: 90.0,
+			};
+			let actual = camera.to_mat4();
+			let expected = projection(y_angle, 1.0 / camera.y_frac, 10.0)
+				* Affine3A::from_translation(vec3(0., 0., -10.0));
+			let c = expected.x_axis.x / actual.x_axis.x;
+			assert!(
+				(c * actual).abs_diff_eq(expected, 1e-3),
+				"projection at {y_angle_deg}d is wrong\nexpected: {expected}\nexpected: {}\ncomputed: {actual}",
+				expected / c,
+			);
+		}
+	}
 }
diff --git a/src/lib.rs b/src/lib.rs
index 1eae7df..11b45d5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -108,15 +108,22 @@ impl Core {
 	}
 
 	fn render(&self, output: &wgpu::Texture, args: &RedrawArgs) {
-		let aspect = {
+		let y_frac = {
 			let size = output.size();
 			let w = size.width as f32;
 			let h = size.height as f32;
-			w / h
+			h / w
 		};
-		let distance = 0.5 * args.cam_view_y / (0.5 * args.cam_view_angle).tan();
-		let view = Mat4::from(camera::view(args.cam_yaw, args.cam_pitch, distance));
-		let proj = camera::projection(args.cam_view_angle, aspect, distance);
+		let proj = camera::Camera {
+			y_frac,
+			y_angle: args.cam_view_angle,
+			y_range: args.cam_view_y,
+			z_min: -0.5 * args.cam_view_y,
+			z_max: 0.5 * args.cam_view_y,
+		}
+		.clamp_z_min(0.01 * args.cam_view_y)
+		.to_mat4();
+		let view = Mat4::from_mat3(camera::rotation(-args.cam_yaw, -args.cam_pitch));
 		self.mesh_pipeline.set_params(
 			&self.queue,
 			render::mesh::Params {
diff --git a/ui/src/main_window.ui b/ui/src/main_window.ui
index 19d28a8..748c5e2 100644
--- a/ui/src/main_window.ui
+++ b/ui/src/main_window.ui
@@ -143,7 +143,7 @@
            <number>1</number>
           </property>
           <property name="minimum">
-           <double>15.000000000000000</double>
+           <double>0.000000000000000</double>
           </property>
           <property name="maximum">
            <double>150.000000000000000</double>