Cardboard Box and Stealth Components (#11569)

Content.Client/Stealth/StealthSystem.cs

@@ -0,0 +1,74 @@
+using Content.Client.Interactable.Components;
+using Content.Shared.Stealth;
+using Content.Shared.Stealth.Components;
+using Robust.Client.GameObjects;
+using Robust.Client.Graphics;
+using Robust.Shared.Prototypes;
+
+namespace Content.Client.Stealth;
+
+public sealed class StealthSystem : SharedStealthSystem
+{
+    [Dependency] private readonly IPrototypeManager _protoMan = default!;
+
+    private ShaderInstance _shader = default!;
+
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        _shader = _protoMan.Index<ShaderPrototype>("Stealth").InstanceUnique();
+        SubscribeLocalEvent<StealthComponent, ComponentRemove>(OnRemove);
+        SubscribeLocalEvent<StealthComponent, BeforePostShaderRenderEvent>(OnShaderRender);
+    }
+
+    protected override void OnInit(EntityUid uid, StealthComponent component, ComponentInit args)
+    {
+        base.OnInit(uid, component, args);
+        if (!TryComp(uid, out SpriteComponent? sprite))
+            return;
+
+        sprite.PostShader = _shader;
+        sprite.GetScreenTexture = true;
+        sprite.RaiseShaderEvent = true;
+
+        if (TryComp(uid, out InteractionOutlineComponent? outline))
+        {
+            RemComp(uid, outline);
+            component.HadOutline = true;
+        }
+    }
+
+    private void OnRemove(EntityUid uid, StealthComponent component, ComponentRemove args)
+    {
+        if (!TryComp(uid, out SpriteComponent? sprite))
+            return;
+
+        sprite.PostShader = null;
+        sprite.GetScreenTexture = false;
+        sprite.RaiseShaderEvent = false;
+        sprite.Color = Color.White;
+
+        if (component.HadOutline)
+            AddComp<InteractionOutlineComponent>(uid);
+    }
+
+    private void OnShaderRender(EntityUid uid, StealthComponent component, BeforePostShaderRenderEvent args)
+    {
+        // Distortion effect uses screen coordinates. If a player moves, the entities appear to move on screen. this
+        // makes the distortion very noticeable.
+
+        // So we need to use relative screen coordinates. The reference frame we use is the parent's position on screen.
+        // this ensures that if the Stealth is not moving relative to the parent, its relative screen position remains
+        // unchanged.
+        var parentXform = Transform(Transform(uid).ParentUid);
+        var reference = args.Viewport.WorldToLocal(parentXform.WorldPosition);
+        var visibility = GetVisibility(uid, component);
+        _shader.SetParameter("reference", reference);
+        _shader.SetParameter("visibility", visibility);
+
+        visibility = MathF.Max(0, visibility);
+        args.Sprite.Color = new Color(visibility, visibility, 1, 1);
+    }
+}
+