Raymarched Fog Volumes for Unity's Universal RP

This repository is an implementation of single-bounce raymarched volumetric fog for Unity's Universal Render Pipeline.

Scenes	Outdoors Light Shafts	URP Samples- Japanese Garden	Nighttime streetlights
Fog
No Fog

More Examples

Installation

• Open the package manager and select the Add package from Git URL option found under the top left dropdown.
  
  
• Add this repository git URL in the prompt, using the following link: https://github.com/sinnwrig/URP-Fog-Volumes.git.
  
  

Features

• Half & quarter-resolution rendering with depth-aware upsampling (Incompatible with temporal rendering).
• Temporal Rendering with reprojection (Semi-complete).
• Animated scrolling 3D texture noise
• 4 primitive shapes that support non-uniform scale and rotation:
  • Cube
  • Capsule
  • Sphere
  • Cylinder
• Support for all realtime lights, shadows, and cookies up to a maximum of 32 lights per volume.
  
  • Lighting is not entirely physically-based, and instead exposes artistic controls for finer tweaking.
    
  • Light attenuation is only single-bounce, and fog does not self-shadow. Multiple-bounce lightmarching will be added soon.
    
• Support for APV GI in Unity 2023.1+
• Samples for the Gas Station, Forest, and Office Building scenes. These can be imported through the package manager.

Usage

• Add the Fog Volume Render Feature to your renderers.
• Create a new Fog Volume in the scene by adding the FogVolume component to any object or using the options under GameObject/Volumes/
• Create or assign a new profile.
• Adjust object scale and profile settings until you get your desired look.

Limitations

Unresolvable

• Does not support DirectX 9 (Desktop GPUs before 2009~2011) or DirectX 11 9.x (DirectX version specifically for Windows Phone and Microsoft Surface RT). These shader models are incompatible with dynamic loops.
• Temporal Reprojection is disabled in scene view, and only works when in play mode. Unity does not seem to generate consistent motion vectors for the editor view, and causes severe warping/blurring.
• Temporal Reprojection cannot reproject parts where fog is facing the skybox or empty space. Motion vectors can't be created where there are no discernible features to track and compute movement.
• There is currently a hard cap of 32 lights per volume. This cap can be changed by editing the maximum light constants in VolumetricFog.shader and FogVolume.cs

Under Development

• Does not use physically based light scattering through the volume, as lighting is single-bounce only. This means that for directional lights, volumes will be evenly lit regardless of density. Lightmarching is planned on being added.
• Orthographic cameras do not work. This is planned on being fixed.
• Baked lighting and light probes does not work at the moment. This is planned on being fixed.

Transparency Handling

Due to how transparent objects are rendered to the depth texture, transparency does not work out-of-the-box with Fog Volumes and requires some additional render feature setup detailed in this Forum Post, although a brief tutorial will be provided:

1. Put all the transparent renderers you want affected by fog into their own seperate layer (i.e 'TransparentDepth).
2. Remove the layer created just now from the Transparent Layer Mask field in the Filtering section of your active URP renderers. These objects will instead be rendered using the render feature.
3. Add the Render Objects render feature to your renderers before the Fog Volume render reature.
4. Set the Event field of Render Objects to AfterRenderingTransparents
5. Under Filters, set the queue to Transparent and the layer mask to our custom transparent depth layer.
6. Under Overrides, override Depth and enable Write Depth and set the Depth Test to Less Equal

Potential Issues

I am confident the the asset in its current state has no glaring or overly apparent issues. That said, this asset is not backed by heavy testing, and there is a chance that this package may have bugs or not work on some platforms.

This asset has been tested on:

• OpenGL 4.5.
• DirectX 11.
• DirectX 12.
• Vulkan.
• Unity version 2022.3.
• Windows.
• Linux.

This asset has not been tested, but may work on:

• Metal.
• VR or AR platforms.
• Versions of Unity below 2022.3.
• macOS.
• PlayStation devices.
• Xbox devices.
• Nintendo devices.
• iOS.
• visionOS.
• Android.
• WebGL.
• UWP.
• tvOS.

Examples

Japanese Forest with and without fog

Oasis with and without fog

Building with and without fog

Japanese Garden with and without fog

Gas station with and without fog

Demo Terminal Building with fog