RenderHooks

<cat>Code.Rendering</cat>
<title>RenderHooks</title>
<warning>the code examples on this page were written for the entity system and may be outdated or incorrect</warning>

# 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.AfterPostProcess )
		{
			Graphics.Clear( Color.Green );
		}
	}
}
```

This renders after the post process stage.. which means that the 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 );
		}
	}
}
```

RenderHooks

Account Management

Special Pages

Wiki List

S&box Wiki