Rendering the output

To set up a custom render pipeline with render passes you’ll first need a patch representing the Screen Output property of the Device scene object. You can either:

• Add this patch individually.
• Add a pre-made patch graph that includes the Screen Output patch, setting up a default render pipeline you can then edit.

Adding the Screen Output patch individually

To create this patch:

1. Select the Device in the Scene panel.
2. Go to the Inspector.
3. Click the circle on the left of Render Pass.

A consumer patch labeled Screen Output will be added to the Patch Editor:

What’s rendering is now driven by patches. Because there are no patches connected to the Screen Output patch the Simulator video will be replaced by a blue screen:

The default render pipeline

This is patch graph that includes a Scene Render Pass patch, creating a complete render pipeline.

To create this graph:

1. Select the Device in the Scene panel.
2. In the Inspector, go to Default Pipeline.
3. Click the Create button.

A graph will be added to the Patch Editor, containing a:

• Screen Output patch.
• Scene Render Pass patch.
• Patch representing the camera texture.
• Patch representing the Device scene object.

The camera texture patch is connected to the Background input in the Scene Render Pass patch. This renders the camera texture across the background of the scene.

The patch representing the device is connected to the Scene Object input port, rendering all children of the Device in the Scene panel over the input in the Background port.

In the image below we’ve added the default render pipeline to a scene featuring 3D text. The 3D text renders over the camera texture:

Without the camera texture patch the background of the scene is black by default:

To edit the background color, adjust the Default Color value in the patch.

The output of the Scene Render Pass patch is an image. The render size of the image can be set using the Size values in the Scene Render Pass patch.

Limitations

You can’t use the face tracker texture with render passes. You should use the Face Extraction Render Pass instead.

Scene Render Pass patches won’t render an alpha channel.

Best Practices

Planning

Using a custom render pipeline will impact how you arrange your scene hierarchy, so plan your effect and rendering strategy in advance.

Testing

As with any AR effect, test early and iterate, adding complexity as you go.

Because large render pipelines can impact performance, it’s important to test on a range of devices.

Building your graph

Before you connect any type of render pass patch to another, you can see a preview of how your effect will look after connecting the patches. The preview is hidden by default, open the preview by clicking on the arrow on the bottom right of the patch.

In the example below we’re changing the Multiplier value in the Gaussian Blur patch to adjust the output of the Shader Render Pass patch it’s connected to. This causes the preview image to become more or less blurry

Visually debug your graph by frequently moving the Screen Output patch, connecting it at different stages.

To improve efficiency, take a non-linear approach — rather than render something again, recycle it from an earlier stage of your visual shader graph.