<cat>Code.Camera</cat>⤶ <cat>Code.Rendering</cat>⤶ <title>RenderHooks</title> # What are RenderHooks Render Hooks allow you to run your code during certain points in the render pipeline. For example * Drawing post process before UI * Drawing effects before the viewmodel is rendered # How to create them A simple renderhook that renders the screen green looks like this. ``` internal class MyRenderHook : RenderHook { public Color MyColor { get; set; } public override void OnStage( SceneCamera target, Stage renderStage ) { if ( renderStage == Stage.BeforeViewmodel ) { Graphics.Clear( Color.Green ); } } } ``` This renders before the viewmodel.. which means that the viewmodel and post processing and UI will be drawn on top of it. <upload src="1/8daa0471dfb1a92.jpg" size="43131" name="sbox_0194.jpg" /> # How to add to a camera Renderhooks need to be added to a SceneCamera. The main game's SceneCamera is available at `Map.Camera`. So clientside, in some function like `FrameSimulate` you might do something like this. ``` var hook = Map.Camera.FindOrCreateHook<MyRenderHook>(); hook.Enabled = IsPlayerDead(); hook.MyColor = Color.Random; ``` Alternatively, if you're gonna want your renderhook to be called every frame on the main game camera you can add this attribute to it. ``` [SceneCamera.AutomaticRenderHook] ``` # OnFrame In your renderhook OnFrame will be called immediately before every frame. If what you're doing involves moving/creating/placing/adjusting SceneObjects then this is a great place to do it. # Example ``` [SceneCamera.AutomaticRenderHook] public partial class MyPostProcessEffect : RenderHook { RenderAttributes attributes = new RenderAttributes(); Material effectMaterial = Material.Load( "materials/my_awesome_material.vmat" ); public override void OnStage( SceneCamera target, Stage renderStage ) { // Don't render is local pawn is dead if ( Local.Pawn.Health <= 0 ) return; if ( renderStage == Stage.BeforePostProcess ) { // Set some dumb attributes attributes.Set( "CameraFOV", target.FieldOfView.DegreeToRadian() ); attributes.Set( "PawnHealth", Local.Pawn.Health / 100.0f ); // Grab the current screen texture and put it in "ColorBuffer" Graphics.GrabFrameTexture( "ColorBuffer", attributes ); // Draw our effect material, which is probably using a special post process // shader that uses all the attributes to do cool effects Graphics.Blit( effectMaterial, attributes ); } } } ```