gaemstone/src/gaemstone.Client/Modules/CameraModule.cs

using System;
using gaemstone.ECS;
using Silk.NET.Input;
using Silk.NET.Maths;
using static gaemstone.Client.Input;

namespace gaemstone.Client;

[Module]
[DependsOn(typeof(Input))]
public class CameraModule
{
	[Component]
	public struct Camera
	{
		public static readonly Camera Default2D = Create2D();
		public static readonly Camera Default3D = Create3D(80.0F);

		public static Camera Create2D(float nearPlane = -100.0F, float farPlane = 100.0F)
			=> new() { NearPlane = nearPlane, FarPlane = farPlane };
		public static Camera Create3D(float fieldOfView, float nearPlane = 0.1F, float farPlane = 200.0F)
			=> new() { FieldOfView = fieldOfView, NearPlane = nearPlane, FarPlane = farPlane };

		public float FieldOfView { get; set; }
		public float NearPlane { get; set; }
		public float FarPlane { get; set; }

		public bool IsOrthographic => (FieldOfView == 0.0F);
	}

	[Component]
	public struct CameraViewport
	{
		public Vector4D<byte> ClearColor { get; set; }
		public Rectangle<int> Viewport { get; set; }
	}

	[Component]
	public struct CameraController
	{
		public float MouseSensitivity { get; set; }
		public Vector2D<float>? MouseGrabbedAt { get; set; }
	}

	[System]
	public static void UpdateCamera(TimeSpan delta, in Camera camera,
		ref GlobalTransform transform, ref CameraController controller,
		[Source(typeof(Game))] RawInput input)
	{
		var isMouseDown    = input.IsDown(MouseButton.Right);
		var isMouseGrabbed = controller.MouseGrabbedAt != null;
		if (isMouseDown != isMouseGrabbed) {
			if (isMouseDown) controller.MouseGrabbedAt = input.MousePosition;
			else controller.MouseGrabbedAt = null;
		}

		if (controller.MouseGrabbedAt is not Vector2D<float> pos) return;

		var mouseMoved = input.MousePosition - pos;
		input.Context!.Mice[0].Position = pos.ToSystem();

		var dt = (float)delta.TotalSeconds;
		var xMovement = mouseMoved.X * dt * controller.MouseSensitivity;
		var yMovement = mouseMoved.Y * dt * controller.MouseSensitivity;

		if (camera.IsOrthographic) {
			transform *= Matrix4X4.CreateTranslation(-xMovement, -yMovement, 0);
		} else {
			var speed = dt * (input.IsDown(Key.ShiftLeft) ? 12 : 4);
			var forwardMovement = ((input.IsDown(Key.W) ? -1 : 0) + (input.IsDown(Key.S) ? 1 : 0)) * speed;
			var sideMovement    = ((input.IsDown(Key.A) ? -1 : 0) + (input.IsDown(Key.D) ? 1 : 0)) * speed;

			var curTranslation = new Vector3D<float>(transform.Value.M41, transform.Value.M42, transform.Value.M43);
			var yawRotation   = Matrix4X4.CreateRotationY(-xMovement / 100, curTranslation);
			var pitchRotation = Matrix4X4.CreateRotationX(-yMovement / 100);
			var translation   = Matrix4X4.CreateTranslation(sideMovement, 0, forwardMovement);

			transform = translation * pitchRotation * transform * yawRotation;
		}
	}
}