mark a source

src/main.rs

@@ -1,3 +1,5 @@
+#![feature(gen_blocks)]
+
 use std::{error::Error, f32::consts::PI, sync::Arc};
 
 use glam::{Mat4, vec3};
@@ -11,10 +13,12 @@ use winit::{
 use crate::{
 	camera::OrbitalCamera,
 	render::lines::{LookParams, Mesh, Pipeline, Vertex},
+	trace::Source,
 };
 
 mod camera;
 mod render;
+mod trace;
 
 const TITLE: &str = "WGPU example";
 const OUTPUT_FORMAT: wgpu::TextureFormat = wgpu::TextureFormat::Bgra8UnormSrgb;
@@ -44,6 +48,23 @@ pub fn new_tripod(device: &wgpu::Device) -> Mesh {
 	)
 }
 
+fn loop_list<T: Clone, U>(
+	iter: impl IntoIterator<Item = T>,
+	mut fa: impl FnMut(T) -> U,
+	mut fb: impl FnMut(T) -> U,
+) -> impl Iterator<Item = U> {
+	gen move {
+		let mut iter = iter.into_iter();
+		let Some(first) = iter.next() else { return };
+		yield fa(first.clone());
+		for item in iter {
+			yield fb(item.clone());
+			yield fa(item);
+		}
+		yield fb(first);
+	}
+}
+
 impl MainWindow {
 	fn new(event_loop: &ActiveEventLoop) -> Self {
 		let handle = event_loop
@@ -111,6 +132,29 @@ impl MainWindow {
 			..Default::default()
 		});
 		self.pipeline.render(&mut pass, [&self.tripod]);
+
+		let source = Source {
+			position_yaw: 0.0,
+			position_pitch: PI / 3.,
+			distance: 1.0,
+			diameter: 0.25,
+		};
+		let contour = source.contour(17);
+		let contour: Vec<Vertex> = loop_list(
+			contour,
+			|pos| Vertex {
+				pos,
+				color: vec3(1., 1., 0.),
+			},
+			|pos| Vertex {
+				pos,
+				color: vec3(1., 1., 1.),
+			},
+		)
+		.collect();
+		self.pipeline
+			.render(&mut pass, [&Mesh::new(&self.device, &contour)]);
+
 		drop(pass);
 		self.queue.submit(std::iter::once(encoder.finish()));
 	}

src/trace.rs

@@ -0,0 +1,55 @@
+use std::f32::consts::PI;
+
+use glam::{Mat4, Vec3, vec3};
+
+use crate::camera::OrbitalCamera;
+
+#[derive(Debug, Clone)]
+pub struct Source {
+	/// Horizontal position (angle), in radians from +X towards +Y.
+	pub position_yaw: f32,
+
+	/// Vertical position (angle), in radians from XY plane towards +Z.
+	pub position_pitch: f32,
+
+	/// Distance from the origin.
+	pub distance: f32,
+
+	/// Disc diameter.
+	pub diameter: f32,
+}
+
+impl Source {
+	fn orbital(&self) -> OrbitalCamera {
+		let &Self {
+			position_yaw,
+			position_pitch,
+			distance,
+			..
+		} = self;
+		OrbitalCamera {
+			position_yaw,
+			position_pitch,
+			distance,
+		}
+	}
+
+	pub fn position(&self) -> Vec3 {
+		self.orbital().position()
+	}
+
+	pub fn transform(&self) -> Mat4 {
+		self.orbital().transform().inverse()
+	}
+
+	pub fn contour(&self, n: usize) -> impl Iterator<Item = Vec3> {
+		let step = 2. * PI / n as f32;
+		let r = 0.5 * self.diameter;
+		let m = self.transform();
+		(0..n).map(move |k| {
+			let angle = (k as f32) * step;
+			let (x, y) = angle.sin_cos();
+			m.transform_point3(r * vec3(x, y, 0.))
+		})
+	}
+}