s&box

Weapons/ScreenWeapon.cs
A weapon component that manages a small render-to-texture screen on the weapon viewmodel. It creates a render target, replaces the model material with a copy that uses the render texture as an emissive, updates an attached command list to draw the screen each frame, and provides helpers for coil spin and joystick animation.
Native Interop
using Sandbox.Rendering;

public partial class ScreenWeapon : BaseSandboxWeapon
{
	private Material _screenMaterialCopy;
	private Texture _screenTexture;
	private float _coilSpin;
	private float _joystickX;
	private float _joystickY;
	private TimeSince _lastScreenUpdate;

	/// <summary>
	/// Override to match a different model's screen material.
	/// </summary>
	protected virtual string ScreenMaterialName => "toolgun_screen";

	/// <summary>
	/// Override to use a different screen material
	/// </summary>
	protected virtual string ScreenMaterialPath => "weapons/toolgun/toolgun-screen.vmat";

	protected virtual Vector2Int ScreenTextureSize => new( 512, 128 );

	/// <summary>
	/// Minimum time in seconds between screen redraws
	/// </summary>
	protected virtual float ScreenRefreshInterval => 0f;

	/// <summary>
	/// Add energy to the coil spin (e.g. on fire).
	/// </summary>
	public void SpinCoil()
	{
		_coilSpin += 10;
	}

	/// <summary>
	/// Smoothly decays the coil spin and applies it to the viewmodel's "coil" object.
	/// </summary>
	protected void ApplyCoilSpin()
	{
		_coilSpin = _coilSpin.LerpTo( 0, Time.Delta * 1 );

		if ( !ViewModel.IsValid() ) return;

		var coil = ViewModel.GetAllObjects( true ).FirstOrDefault( x => x.Name == "coil" );
		if ( coil.IsValid() )
		{
			coil.WorldRotation *= Rotation.From( 0, 0, _coilSpin );
		}
	}

	/// <summary>
	/// Updates joystick_x and joystick_y on the viewmodel based on a per-frame look delta.
	/// </summary>
	public void UpdateJoystick( Angles lookDelta )
	{
		_joystickX = _joystickX.LerpTo( lookDelta.yaw.Clamp( -1f, 1f ), Time.Delta * 10f );
		_joystickY = _joystickY.LerpTo( lookDelta.pitch.Clamp( -1f, 1f ), Time.Delta * 10f );

		WeaponModel?.Renderer?.Set( "joystick_x", _joystickX );
		WeaponModel?.Renderer?.Set( "joystick_y", _joystickY );
	}

	public void SetIsUsingJoystick( bool isUsing )
	{
		WeaponModel?.Renderer?.Set( "b_joystick", isUsing );
	}

	/// <summary>
	/// Updates the viewmodel screen render target and redraws it.
	/// </summary>
	protected void UpdateViewmodelScreen()
	{
		if ( !ViewModel.IsValid() ) return;

		var modelRenderer = ViewModel.GetComponentInChildren<SkinnedModelRenderer>();
		if ( !modelRenderer.IsValid() ) return;

		// Clear any previously assigned command list so it only executes once per update
		modelRenderer.ExecuteBefore = null;

		if ( ScreenRefreshInterval > 0f && _lastScreenUpdate < ScreenRefreshInterval )
			return;

		_lastScreenUpdate = 0;

		var oldMaterial = modelRenderer.Model.Materials.FirstOrDefault( x => x.Name.Contains( ScreenMaterialName ) );
		var index = modelRenderer.Model.Materials.IndexOf( oldMaterial );
		if ( index < 0 ) return;

		_screenTexture ??= Texture.CreateRenderTarget().WithSize( ScreenTextureSize.x, ScreenTextureSize.y ).WithInitialColor( Color.Red )
			.Create();

		_screenMaterialCopy ??= Material.Load( ScreenMaterialPath ).CreateCopy();
		_screenMaterialCopy.Attributes.Set( "Emissive", _screenTexture );
		modelRenderer.SceneObject.Attributes.Set( "Emissive", _screenTexture );

		modelRenderer.Materials.SetOverride( index, _screenMaterialCopy );

		UpdateViewScreenCommandList( modelRenderer );
	}

	private void UpdateViewScreenCommandList( SkinnedModelRenderer renderer )
	{
		var rt = RenderTarget.From( _screenTexture );

		var cl = new CommandList( "ScreenWeaponViewScreen");
		renderer.ExecuteBefore = cl;

		cl.SetRenderTarget( rt );
		cl.Clear( Color.Black );

		DrawScreenContent( new Rect( 0, _screenTexture.Size ), cl.Paint );

		cl.ClearRenderTarget();
	}

	/// <summary>
	/// Override this to draw custom content onto the viewmodel screen.
	/// </summary>
	protected virtual void DrawScreenContent( Rect rect, HudPainter paint )
	{
	}
}