1 files changed, 187 insertions, 0 deletions
diff --git a/render/src/camera.rs b/render/src/camera.rs
new file mode 100644
index 0000000..ecece90
--- /dev/null
+++ b/render/src/camera.rs
@@ -0,0 +1,187 @@
+use std::mem::size_of;
+
+use cgmath::{Matrix4, Vector2};
+
+#[derive(Debug)]
+pub struct Camera {
+	position: (f32, f32),
+	zoom: f32,
+	rotation: f32,
+	inverse_aspect_ratio: f32,
+	buffer: wgpu::Buffer,
+	bind_group: wgpu::BindGroup,
+}
+
+type CameraUniform = [[f32; 4]; 4];
+
+#[allow(clippy::cast_precision_loss)]
+fn inverse_aspect_ratio(width: u32, height: u32) -> f32 {
+	(height as f32) / (width as f32)
+}
+
+impl Camera {
+	/// Create a new camera, with a position of (0, 0), and a zoom of 1.0
+	pub(crate) fn new(
+		device: &wgpu::Device,
+		width: u32,
+		height: u32,
+	) -> (Self, wgpu::BindGroupLayout) {
+		let buffer = device.create_buffer(&wgpu::BufferDescriptor {
+			label: Some("Camera Uniform"),
+			size: size_of::<CameraUniform>() as wgpu::BufferAddress,
+			usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
+			mapped_at_creation: false,
+		});
+
+		let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+			label: Some("Camera Bind Group Layout"),
+			entries: &[wgpu::BindGroupLayoutEntry {
+				binding: 0,
+				visibility: wgpu::ShaderStages::VERTEX,
+				ty: wgpu::BindingType::Buffer {
+					ty: wgpu::BufferBindingType::Uniform,
+					has_dynamic_offset: false,
+					min_binding_size: None,
+				},
+				count: None,
+			}],
+		});
+
+		let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
+			label: Some("Camera Bind Group"),
+			layout: &bind_group_layout,
+			entries: &[wgpu::BindGroupEntry {
+				binding: 0,
+				resource: buffer.as_entire_binding(),
+			}],
+		});
+
+		(
+			Self {
+				position: (0.0, 0.0),
+				zoom: 1.0,
+				rotation: 0.0,
+				inverse_aspect_ratio: inverse_aspect_ratio(width, height),
+				buffer,
+				bind_group,
+			},
+			bind_group_layout,
+		)
+	}
+
+	/// Get the camera's current x position
+	#[must_use]
+	pub const fn x(&self) -> f32 {
+		self.position.0
+	}
+
+	/// Get the camera's current y position
+	#[must_use]
+	pub const fn y(&self) -> f32 {
+		self.position.1
+	}
+
+	/// Get the camera's current zoom
+	#[must_use]
+	pub const fn zoom(&self) -> f32 {
+		self.zoom
+	}
+
+	/// Get the camera's current rotation, in radians
+	#[must_use]
+	pub const fn rotation(&self) -> f32 {
+		self.rotation
+	}
+
+	/// Set the position of the camera
+	pub fn set_position(&mut self, x: f32, y: f32) {
+		#[cfg(debug_assertions)]
+		if !(-1000.0..1000.0).contains(&x) || !(-1000.0..1000.0).contains(&y) {
+			log::warn!(
+				"The position of the camera is (x: {}, y: {}). \
+				Please keep both the x and y positions above -1000 and below 1000 units. \
+				Otherwise, everything will look crazy. \
+				For an explanation, see https://www.youtube.com/watch?v=Q2OGwnRik24",
+				x,
+				y
+			);
+		}
+
+		self.position = (x, y);
+	}
+
+	/// Set the zoom of the camera
+	pub fn set_zoom(&mut self, zoom: f32) {
+		#[cfg(debug_assertions)]
+		if !(-1000.0..1000.0).contains(&zoom) {
+			log::warn!(
+				"The zoom of the camera is {}. \
+				Please keep above -1000, and below 1000, or else smooth zoom may be difficult. \
+				For an explanation, see https://www.youtube.com/watch?v=Q2OGwnRik24",
+				zoom
+			);
+		}
+
+		self.zoom = zoom;
+	}
+
+	/// Set the camera rotation, in radians
+	pub fn set_rotation(&mut self, rotation: f32) {
+		self.rotation = rotation % std::f32::consts::TAU;
+	}
+
+	/// Set the aspect ratio of the camera
+	pub(crate) fn set_size(&mut self, width: u32, height: u32) {
+		self.inverse_aspect_ratio = inverse_aspect_ratio(width, height);
+	}
+
+	/// Create a matrix that can be multiplied by any vector to transform it
+	/// according to the current camera
+	#[allow(clippy::wrong_self_convention)]
+	fn to_matrix(&self) -> CameraUniform {
+		let cos = self.rotation.cos();
+		let sin = self.rotation.sin();
+
+		let x_axis = Vector2::new(cos, -sin);
+		let y_axis = Vector2::new(sin, cos);
+
+		let eye = Vector2::new(self.position.0, self.position.1);
+		let x_dot = -cgmath::dot(x_axis, eye);
+		let y_dot = -cgmath::dot(y_axis, eye);
+
+		#[rustfmt::skip]
+		let view_matrix = Matrix4::new(
+			x_axis.x, y_axis.x, 0.0, 0.0,
+			x_axis.y, y_axis.y, 0.0, 0.0,
+			0.0, 0.0, 1.0, 0.0,
+			x_dot, y_dot, 0.0, 1.0
+		);
+
+		#[rustfmt::skip]
+		// TODO implement more scaling coordinate systems
+		let projection_matrix = Matrix4::new(
+			self.inverse_aspect_ratio * self.zoom, 0.0, 0.0, 0.0,
+			0.0, self.zoom, 0.0, 0.0,
+			0.0, 0.0, 1.0 / 256.0, 0.0,
+			0.0, 0.0, 0.0, 1.0
+		);
+
+		let transform = projection_matrix * view_matrix;
+		transform.into()
+	}
+
+	/// Get the bind group for the camera
+	pub(crate) const fn bind_group(&self) -> &wgpu::BindGroup {
+		&self.bind_group
+	}
+
+	/// Refresh the camera buffer for the next frame
+	#[profiling::function]
+	pub(crate) fn refresh(&self, queue: &wgpu::Queue) {
+		queue.write_buffer(
+			&self.buffer,
+			0 as wgpu::BufferAddress,
+			bytemuck::cast_slice(&self.to_matrix()),
+		);
+	}
+}