Hx Volumetric Lighting

Hx Volumetric Lighting is a Unity asset that enables volumetric dynamic lighting in your scene, adding depth and realism with rays of light and fog of variable density. It's easy to use and runs efficiently.


  • Supports shadow casting lights.
  • Supports multiple lights - any number and combination of point lights, spot lights, and directional lights.
  • Vary the air density with particle emitters or 3D noise.
  • Use height fog to get a low hanging fog look.
  • Supports transparency.
  • Supports light cookies.
  • Efficient and high performance, allowing for high framerates.
  • Easy to use. Just drop a few scripts on your camera and lights.
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Hx Volumetric Lighting is the easiest way to get high quality volumetric lighting in your Unity scene. Follow this guide to get started, and let us know if you have any questions or comments.


Take these requirements under consideration when using Hx Volumetric Lighting:


  1. Add the HxVolumetricCamera.cs script to each camera you want to render volumetric lighting on.
  2. Add the HxVolumetricLight.cs script to each light in your scene that you want to be volumetric.
  3. Adjust the settings in your camera inspector to fit the style of your project.
  4. (Optional) To vary the air density using particle emitters, put the HxVolumetricParticleSystem.cs script on your emitters and follow the instructions for particle density.
  5. (Optional) If your scene has objects with transparency, you may need to slightly modify your shaders so they properly render. You can find these instructions in the transparency section.

If you are not using HDR rendering on your camera, the volumetric effect will automatically be converted to LDR. If you are using HDR, It is recommended that you use tone mapping. Otherwise, you can enable the Map To LDR setting in the Advanced Settings section, and it will handle tone mapping for you. However, it is recommended that you use an external tone mapper.


In your camera's inspector window, you can adjust several parameters to control the volumetric effect.

Light Scattering Settings

These set the default values for the lights. You can overwrite them on a per-light basis by selecting custom settings in the inspector window for each light, although it is recommended to use this sparingly, as conflicting extinction values can cause some artifacts for overlapping lights.


A higher density value will result in more visible light scattering, but will also make your scene more foggy.

Mie Scattering

This value describes the angular light scattering amount. A low value will scatter the light evenly in all directions, while a high value will scatter the light more in the direction of the light. At high values, being in the direct path of the light direction and looking directly at the light source will give you a blown out, staring-into-the-sun effect.

From left to right, lower to higher values of Mie scattering with a point light.

Lower to higher values of Mie scattering with a spot light.

A side view of the same lights as the spot light above.

Ambient Lighting Strength

You can use this value to mix the scene's ambient lighting into the volumetric pass. This uses Unity's ambient lighting settings, found in the options under Window->Lighting. This supports all three ambient sources — skybox, gradient, and color — when using deferred rendering mode. Skybox is not currently supported in forward rendering mode.

Ambient light can soften up your scene.

This is the same scene with ambient lighting turned off. Click on each image to enlarge them and compare.


Extinction describes the brightness of the scattered light. A higher extinction value causes the light to fade more as it travels through dense air.

Extinction Effect

This darkens the rendered pixel color based on the air density and the extinction amount. This only works if a volumetric directional light is in the scene.

Sun Size

This value allows you to create a sun-like effect when looking directly at a light source. This effect can look bad if you have a low sample rate or are rendering at quarter resolution.

Sun size is at 0 on the left, and 1 on the right, creating a sun effect.

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Fog Height Settings

The height fog feature modifies the fog amount based on height. You can use this to achieve a ground-based fog effect.

A scene with fog height enabled, giving the effect of extra density on the ground.

Height Fog Enabled

Select this to activate fog height.

Fog Height

The fog above this height is scaled by the Above Fog Percent value.

Fog Transition Height

The fog below this height is equal to the global air density (the same amount as if Height Fog is not activated). The fog between this value and the Fog Height linearly transitions from the global air density to the value scaled by the Above Fog Percent.

Above Fog Percent

This percentage scales the fog amount for fog above the Fog Height. Choose a value between 0 and 1.

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Noise Settings

3D Noise can be added to the air density, which makes the air look less homogeneous.

The right image has a subtle amount of noise enabled.

Noise Enabled

Select this to enable the 3D noise.

Noise Scale

This adjusts the scaling of the noise to alter the amount of detail to the noise.

Noise Velocity

You can add movement to the noise by adjusting this vector, which controls the direction and magnitude of the movement.

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Particle Density Settings

You can control the air density in an area simply by using particle emitters with a HxVolumetricParticleSystem.cs script attached. In that script, you can set the particle density, which uses the alpha channel of the main texture. You can disable the renderer on the emitter if you only want to modulate the fog value without drawing the particle.

The left image shows particle emitters modulating the air density, while the right image has the feature disabled.

Particle Density Support

Check this to enable support for particle density.

Density Resolution

The particle density feature uses a 3D grid that the emitters render into. This setting controls the scale of the 3D grid, letting you make a tradeoff between speed and detail. It will not render out to a higher value than the Resolution setting in General Settings.

Density Distance

This parameter specifies the distance of the last slice of the 3D grid. If you have a 2.5D game without much depth, you can reduce this value to get more detail, since it is not stretched as far.

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Transparency Settings

Objects with transparent shaders can be modified to work with Hx Volumetric Lighting. Like the particle density feature, the volumetric lighting will be rendered into a 3D grid with which transparent objects can sample when compositing. Included in this package are modified versions of the standard Unity shaders that allow for transparency with this system. When you select a shader for your material, you can find the modified standard shader under HxVolumetric->Standard.

Transparency support is enabled in the left image, allowing for proper rendering of the windows. When compositing transparent objects into the scene, extra information needs to be rendered out in a 3D texture, otherwise it doesn't know how much volumetric lighting is in front and behind it.

Transparency Support

Check this to activate support for transparency.

Transparency Distance

This is the distance of the last slice in the grid. Like the particle density grid, if you have a 2.5 game without much depth, you can reduce this value to get more detail.

Blur Transparency

This setting blurs transparent areas, removing grainy effects. It will introduce some bleeding. The recommended setting is 1.

Transparency blur is enabled in the left image, and disabled in the right image.

Enabling transparency support in custom shaders

If you are using a custom shader, you will need to make some minor modifications in it to get transparency working. Modified versions of the Unity shaders are included in this package, which you can find under HxVolumetric->Standard.

Modify your shader by adding this line to the top:

#include "Assets/Plugins/HxVolumetricLighting/BuiltIn-Replacement/HxVolumetricCore.cginc"

Add this line to each transparent pass:


You will need data to reconstruct the world position. If you don't have it, add this definition to the vertex shader struct, substituting n for the number of the next free TEXCOORD in your vertex struct:

#ifdef VTRANSPARENCY_ON float4 projPos : TEXCOORDn; #endif

Then add this to your vertex shader:

#ifdef VTRANSPARENCY_ON o.projPos = ComputeScreenPos(o.pos); COMPUTE_EYEDEPTH(o.projPos.z); #endif

In your fragment shader, in the first pass, modify your final output with this code:

#ifdef VTRANSPARENCY_ON return VolumetricTransparencyBase(your_output_value, i.projPos); #else return your_output_value; #endif

In any additional passes, use this code:

#ifdef VTRANSPARENCY_ON return VolumetricTransparencyAdd(your_output_value, i.projPos); #else return your_output_value; #endif
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General Settings


This is the resolution that the volumetric lighting is rendered at. Quarter resolution is recommended for a mid-range GPU.

Sample Count

You can adjust the amount of samples used in the raymarching step of the lighting system. Higher values will give better signal fidelity, although with a tradeoff in framerate.

Directional Sample Count

This controls the raymarching sample count for direction lights, since you generally want a higher sample count for a directional light compared to a spot or point light.

Max Directional Ray

This is the maximum distance from the camera that should be sampled for directional lights. Limiting this distance can reduce over-fogging at large distances.

Max Light Distance

This is maximum distance that point lights and spot lights are rendered. Their intensity fades out near the edge of this distance. You can adjust this to disable the volumetric effect on distant lights for a performance increase, although distant lights are already much cheaper to render than closer lights.

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Advanced Settings

Blur Count

This is the amount of depth-aware blur passes. More passes will give better results, but it is an expensive operation. One to two is normally enough.

Blur Depth Falloff

This value is used in the depth-aware blur passes. A lower value will give more even results but will cause bleeding over the edges, giving a bloom-like effect. A higher value will retain object silhouettes, but will result in harsher artifacts. Choose a value appropriate for your art style.

Downsampled Blur Depth

If you are rendering at lower resolutions, this value will be used as the depth falloff.

Upsampled Blur Count

If you are rendering at lower resolutions, it will do a final blur pass to clean up edge artifacts. It's a bit computationally expensive, so set it to 0 if you are okay with edge artifacts.

Depth Threshold

If the depth is within this threshold when upsampling, the result will be bilinearly sampled.

Gaussian Weights

Select this to use a Gaussian weighted blur. This will make the volumetric effect less blurry, but can also make it more splotchy.

Map to LDR

If you are not using HDR on your camera, this option will handle tone mapping for you, although it is recommended that you use an external tone mapper.

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Here are some best practices for improving your run-time performance.

Road Map

These are features which we plan to add in the future:


Hx Volumetric Lighting is created by Hitbox Team. It is part of the lighting system used in the upcoming game, Spire. You can contact us in the following ways: