Example of creating a custom rendering effect using a Render Objects Renderer Feature in URP

The Render Objects Renderer Feature lets you draw objects at a specific point in the frame rendering loop. You can interpret and write rendering data such as depth and stencil in different ways, or draw a set of GameObjects at a certain time.

The following example uses a Render Objects Renderer Feature to draw a GameObject in a different color if it's behind other GameObjects.

A character created from 3 simple capsules for the body and arms. The character is red, but as it moves behind a wall, the hidden parts are rendered blue.

First, create a GameObject and attach it to a new layer.

  1. Create a GameObject in your scene.
  2. In the Inspector window, open the Layer dropdown and add a new layer. You can call the layer DrawBehind.
  3. Set the GameObject to the new layer.

Next, create a Render Objects Renderer Feature that renders only the new layer, on top of the scene.

  1. In the Project window, select the URP Renderer asset your project uses, for example Settings > PC_Renderer.
  2. To create a Render Objects Renderer Feature, select Add Renderer Feature in the Inspector window, then select Render Objects.
  3. To make the Renderer Feature draw only the layer with the GameObject, open the Render Objects (Render Objects) dropdown, then set Layer Mask to the layer.
  4. Set Event to the AfterRenderingOpaques injection point. For more information about custom pass injection points, refer to Custom Pass injection points.

Next, adjust the Renderer Feature so it renders only the parts hidden behind other GameObjects, and in a different color.

  1. Open the Overrides dropdown, then select Depth and set Depth Test to Greater.

    The Renderer Feature now only renders a pixel if its depth is greater than the current pixel in the depth buffer, which means the new pixel is behind another GameObject.

  2. Create a new material that uses the Universal Render Pipeline/Unlit shader.

  3. Set the Base Map color to a color of your choice.

  4. In the Renderer Feature, in the Overrides section, set Material to the material you created.

When you move the GameObject behind other GameObjects, Unity now renders the hidden parts in the color you selected.

The red characters moves behind a wall. Unity renders the hidden parts using a blue material.

Fix overlapping areas of a GameObject

If you use a complex GameObject, the Renderer Feature might draw overlapping parts as though they're hidden. This is because the depth of one part is greater than the overlapping part.

A capsule with a smaller capsule attached. The Renderer Feature renders part of the larger capsule using the blue material, because it's behind the smaller part.

To fix this issue, disable rendering the whole GameObject, and create a new Renderer Feature that renders the non-hidden parts. Follow these steps:

  1. In the URP Renderer asset, open the Opaque Layer Mask dropdown and disable the layer you added.

    Unity now doesn't draw the layer in the opaque render pass. The Renderer Feature still draws the hidden parts, because it's in a different render pass.

    Unity does not draw the character unless it's behind an object

  2. Add a new Render Objects Renderer Feature.

  3. Set Layer Mask to the new layer, so this Renderer Feature draws the GameObject.

  4. Set Event to the AfterRenderingOpaques injection point.

  5. To avoid the first Renderer Feature affecting the depth calculations in the new Renderer Feature, disable Write Depth in the Overrides section of the first Renderer Feature.

The first Renderer Feature draws the hidden parts, and the second Renderer Feature draws the rest of the GameObject.

A character created from 3 simple capsules for the body and arms. The character is red, but as it moves behind a wall, the hidden parts are rendered blue.

Additional resources