Access via Edit > Project Settings > Plugins > IVSmoke

These settings apply globally to all smoke volumes in your project. Settings are saved to DefaultGame.ini.

‍Note: Settings may be reorganized into sub-sections in future updates. The functionality remains the same.

General

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Setting	Type	Default	Description
Enable Smoke Rendering	bool	`true`	Master toggle for the entire IVSmoke rendering system. Disable to turn off all smoke rendering without removing volumes.
Show Advanced Options	bool	`false`	Reveals additional advanced settings in Appearance, Lighting, and Shadows sections. Enable when fine-tuning specific behaviors.

Usage Tips:

Use Enable Smoke Rendering as a global kill switch for performance testing
Enable Show Advanced Options only when you need precise control over edge fade, light override, or shadow bias

Quality

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The Quality section provides a tiered system for balancing visual quality against performance.

Setting	Type	Default	Description
Global Quality	Enum	`Medium (Balanced)`	Master quality preset that controls Ray Marching, Self-Shadow, and External Shadow quality together.

Global Quality Presets

Preset	Ray March Steps	Min Step Size	Self-Shadow	External Shadow	Use Case
Low	128	50.0 cm	3 steps	Off	Mobile/Low-end PC, Maximum performance
Medium	256	25.0 cm	6 steps	On (512px)	Recommended for most projects
High	512	16.0 cm	8 steps	On (1024px)	High-end PC, Maximum quality
Custom	Per-section	Per-section	Per-section	Per-section	Independent control per section

Custom Quality Mode

When Global Quality is set to Custom, you can configure each quality section independently. Each section (Ray March, Self-Shadow, External Shadow) has its own quality preset selector.

Ray March Quality

Setting	Type	Default	Description
Ray March Quality	Enum	`Medium`	Controls ray marching precision. Can be set to Low/Medium/High/Custom.

When Ray March Quality is Custom:

Setting	Type	Range	Default	Description
Custom Max Steps	int32	32-1024	256	Maximum ray marching iterations per pixel
Custom Min Step Size	float	5.0-100.0	25.0	Minimum distance (cm) between ray samples

Self-Shadow Quality

Setting	Type	Default	Description
Self-Shadow Quality	Enum	`Medium`	Controls internal smoke shadowing. Can be set to Off/Low/Medium/High/Custom.

When Self-Shadow Quality is Custom:

Setting	Type	Range	Default	Description
Custom Light Marching Steps	int32	1-16	6	Steps for light direction sampling

External Shadow Quality

Setting	Type	Default	Description
External Shadow Quality	Enum	`Medium`	Controls Cascaded Shadow Map quality. Can be set to Off/Low/Medium/High/Custom.

When External Shadow Quality is Custom:

Setting	Type	Range	Default	Description
Custom Num Cascades	int32	1-6	4	Number of shadow cascade levels
Custom Cascade Resolution	int32	256-2048	512	Shadow map texture resolution
Custom Shadow Max Distance	float	1000-100000	50000	Maximum shadow rendering distance (cm)

Performance Impact

Max Steps: Higher values increase GPU cost linearly
Min Step Size: Smaller values improve quality but require more steps
Cascade Resolution: Memory usage scales quadratically (512x512 = 1MB, 1024x1024 = 4MB per cascade)

Appearance

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Controls the visual characteristics of the smoke.

Setting	Type	Range	Default	Description
Smoke Density Falloff	float	0.0-1.0	0.2	Edge softness. Lower values create softer, more gradual edges. Higher values create sharper, more defined boundaries.
Smoke Size	float	1.0-1000.0	128.0	Scale of the noise sampling. Larger values create bigger, more billowy smoke patterns.
Wind Direction	FVector	-	(0, 0, 0.1)	Direction and speed of wind animation. The magnitude affects speed.

Advanced Options (Show Advanced Options = true)

Setting	Type	Range	Default	Description
Volume Range Offset	float	0.0-1.0	0.1	Offset for volume boundary calculation. Adjusts where smoke starts to appear.
Volume Edge Noise Fade Offset	float	-1.0 to 1.0	0.1	Noise-based fade at volume edges.
Volume Edge Fade Sharpness	float	0.1-10.0	3.0	Sharpness of the edge fade transition. Higher = more abrupt cutoff.

Visual Guide:

Smoke Density Falloff:
  0.0 [====    ] Very soft, gradient edges
  0.5 [======  ] Moderate definition
  1.0 [========] Sharp, hard edges
 
Sharpness:
 -1.0 [  blur  ] Maximum blur
  0.0 [ normal ] No adjustment
  1.0 [ sharp  ] Maximum sharpening

Lighting

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Controls how the smoke interacts with scene lighting.

Setting	Type	Range	Default	Description
Enable Scattering	bool	-	`true`	Enables Rayleigh/Mie scattering simulation for realistic light behavior through smoke.
Scatter Scale	float	0.0-10.0	0.5	Intensity of the scattering effect. Higher values make smoke appear brighter when lit.
Scattering Anisotropy	float	-0.99 to 0.99	0.5	Henyey-Greenstein phase function parameter. Controls light scattering direction.

Scattering Anisotropy Explained:

-0.99: Back-scattering (light bounces back toward source)
 0.00: Isotropic (light scatters equally in all directions)
+0.99: Forward-scattering (light passes through, creating glow effects)
 
Typical values:
  Smoke/Fog: 0.3 ~ 0.6 (slight forward scattering)
  Clouds: 0.7 ~ 0.85 (strong forward scattering, silver lining effect)

Advanced Options (Show Advanced Options = true)

Setting	Type	Default	Description
Override Light Direction	bool	`false`	Use custom light direction instead of Directional Light.
Light Direction Override	FVector	(0, 0, 1)	Custom light direction when override is enabled.
Override Light Color	bool	`false`	Use custom light color instead of Directional Light color.
Light Color Override	FLinearColor	White	Custom light color when override is enabled.

Shadows

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The Shadows section is divided into Self (internal smoke shadows) and External (shadows from scene objects).

Self Shadows

Self-shadowing creates depth within the smoke by calculating how much light is blocked as it travels through the volume.

Setting	Type	Range	Default	Description
Shadow Ambient	float	0.0-1.0	0.2	Minimum brightness in shadowed areas. 0 = pitch black shadows, 1 = no shadows.
Light Marching Distance	float	0.0-500.0	0.0	Maximum distance (cm) to trace toward light. 0 = Automatic (traces until exiting volume).
Light Marching Exp Factor	float	1.0-5.0	2.0	Exponential distribution for light samples. Higher values concentrate samples near the surface.

External Shadows

External shadows allow smoke to receive shadows from scene geometry using Cascaded Shadow Maps (CSM).

Setting	Type	Range	Default	Description
External Shadow Ambient	float	0.0-1.0	0.3	Minimum brightness in externally shadowed areas.
Enable VSM	bool	-	`true`	Use Variance Shadow Maps for softer shadow edges.
VSM Blur Radius	int32	0-8	2	Blur radius for VSM. Higher = softer shadows.
Shadow Depth Bias	float	0.0-100.0	1.0	Bias to prevent shadow acne artifacts.
Capture Skeletal Meshes	bool	-	`false`	Include animated characters in shadow casting. Increases cost.
Cascade Log Linear Blend	float	0.0-1.0	0.85	Blend between logarithmic and linear cascade distribution.
Cascade Blend Range	float	0.0-0.3	0.1	Soft transition range between cascade levels.
VSM Min Variance	float	0.01-100.0	1.0	Minimum variance threshold to prevent light bleeding in thin shadows.
VSM Light Bleeding Reduction	float	0.0-0.5	0.2	Reduces light bleeding artifacts at shadow edges.

Post Processing

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Controls the FXAA anti-aliasing applied specifically to smoke edges.

Setting	Type	Range	Default	Description
FXAA Span Max	float	0.0-4.0	4.0	Maximum edge search distance. Higher values smooth longer edges.
FXAA Range	float	0.0-8.0	1.2	Edge detection threshold. Lower = more aggressive smoothing.
FXAA Sharpness	float	0.1-8.0	1.7	Sharpening applied during FXAA. Counteracts blur from anti-aliasing.

Rendering

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Controls the render pipeline integration.

Setting	Type	Default	Description
Smoke Visual Material	Soft Object Path	None	Optional material for custom smoke visuals.

Advanced Options (Show Advanced Options = true)

Setting	Type	Range	Default	Description
Enable Depth Write	bool	-	`true`	Write smoke depth to scene depth buffer for correct translucent sorting. When enabled, particles behind opaque smoke regions are correctly occluded.
Depth Write Bias	float	0.0-100.0	50.0	Depth bias in centimeters. Positive values push depth further from camera. Helps prevent z-fighting artifacts.

Depth Write System

IVSmoke uses a pre-pass depth write system for correct translucent object sorting:

Ray March Pass - Reads opaque scene depth (before smoke modifies it)
Upscaling & Filtering - Prepares smoke data at full resolution
Depth Write Pass - Writes smoke depth to scene depth buffer

Key characteristics:

Only writes depth for nearly opaque pixels (Alpha >= 0.99)
Executes in pre-pass pipeline before engine's translucent pass
Particles and other translucents are automatically sorted correctly behind opaque smoke regions

When to adjust Depth Write Bias:

Increase if you see z-fighting (flickering) at smoke edges
Decrease if particles appear to "pop through" smoke too early
Default value of 50 cm works well for most use cases

Debug

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Setting	Type	Default	Description
Show Debug Volumes	bool	`false`	Displays wireframe bounds for all smoke volumes in the viewport.

Smoke Preset

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Smoke Presets are Data Assets that define per-volume appearance settings. Use presets to create reusable smoke configurations (white smoke, colored smoke, thick/thin smoke, etc.).

Creating a Smoke Preset

In Content Browser, right-click
Select Miscellaneous > Data Asset
Choose IVSmokeSmokePreset as the class
Name it descriptively (e.g., DA_SmokePreset_WhiteThick)

Preset Properties

Property	Type	Range	Default	Description
Smoke Color	FLinearColor	-	(0.8, 0.8, 0.8, 1.0)	RGB color of the smoke. Alpha is ignored.
Smoke Absorption	float	0.0-1.0	0.1	Light absorption coefficient. Higher values create denser, more opaque smoke.
Volume Density	float	0.0-10.0	1.0	Overall density multiplier for this volume.

Applying a Preset

Select your AIVSmokeVoxelVolume actor in the level
In the Details panel, find IVSmoke | Config > Smoke Preset Override
Assign your Smoke Preset data asset

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Preset Examples

Preset Name	Color	Absorption	Density	Use Case
White Smoke	(0.9, 0.9, 0.9)	0.1	1.0	Standard smoke grenade
Thick Black	(0.1, 0.1, 0.1)	0.3	2.0	Heavy industrial smoke
Red Signal	(0.8, 0.2, 0.1)	0.15	1.2	Signal/marker smoke
Thin Mist	(0.7, 0.7, 0.8)	0.05	0.5	Light fog/mist effect

Translucent Sorting

When smoke needs to correctly sort with translucent objects (like fire effects or glass), IVSmoke uses a Depth Write system.

How It Works

IVSmoke writes smoke depth to the standard scene depth buffer during a pre-pass, before Unreal's translucent pass executes. This allows translucent particles (Niagara/Cascade) and other translucent objects to correctly depth-test against smoke.

Render Pipeline Order:
┌─────────────────────────────┐
│ 1. Opaque Pass              │  ← Scene geometry renders
├─────────────────────────────┤
│ 2. IVSmoke Pre-Pass         │  ← Ray march + Depth Write
│    - Reads opaque depth     │
│    - Writes smoke depth     │
├─────────────────────────────┤
│ 3. Translucent Pass         │  ← Particles read scene depth (includes smoke)
│    - Correct sorting!       │
├─────────────────────────────┤
│ 4. IVSmoke Post-Pass        │  ← Final composite
└─────────────────────────────┘

Automatic Sorting

Unlike previous versions that required Custom Depth configuration, the current Depth Write system works automatically:

No additional setup required for translucent sorting
Particles behind opaque smoke regions are correctly occluded
Only nearly opaque smoke pixels (Alpha >= 0.99) write depth

Troubleshooting

Issue	Solution
Particles appear in front of smoke	Ensure Enable Depth Write is `true` (default)
Z-fighting at smoke edges	Increase Depth Write Bias value
Particles pop through too early	Decrease Depth Write Bias value

Performance

The Depth Write system has minimal performance overhead as it runs as part of the pre-pass pipeline and only writes depth for opaque smoke regions.

Editor Preview

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The Editor Preview feature allows you to preview smoke simulation directly in the editor viewport without entering Play mode.

Starting Preview

Select an AIVSmokeVoxelVolume actor in your level
In the Details panel, find IVSmoke | Debug
Ensure Debug Enabled is checked
Click Start Preview Simulation

The smoke will begin simulating through its lifecycle phases (Expansion → Sustain → Dissipation) directly in the editor viewport.

Stopping Preview

Click Stop Preview Simulation to immediately halt the simulation and clear all voxel data.

Debug Visualization Options

Setting	Type	Default	Description
Debug Enabled	bool	`true`	Master toggle for all debug features.
Render Smoke In Preview	bool	`true`	Whether to render the actual smoke visual during preview.
View Mode	Enum	`Solid Color`	Visualization mode: Solid Color or Heatmap (density-based).
Show Volume Bounds	bool	`true`	Display the bounding box of the smoke volume.
Show Voxel Mesh	bool	`false`	Render each active voxel as a cube mesh. Heavy - use sparingly.
Show Voxel Wireframe	bool	`true`	Draw wireframe cubes for active voxels. Lighter than mesh.
Show Status Text	bool	`true`	Display state, voxel count, and simulation time as floating text.
Debug Wireframe Color	FColor	Dark Gray	Color for debug wireframes.
Slice Height	float	1.0	Display only voxels below this height (0-1 normalized). Useful for inspecting internal structure.
Visible Step Count Percent	int32	100	Percentage of simulation steps to visualize.

Preview Workflow Tips

Rapid Iteration: Adjust Volume parameters, click Start Preview, observe results, stop, adjust, repeat
Use Wireframe Mode: Enable Show Voxel Wireframe to see the simulation structure without heavy mesh rendering
Status Monitoring: Keep Show Status Text enabled to track voxel count and current simulation phase

Limitations

Editor Preview does not trigger network replication
Holes created during preview are local only
Performance in preview may differ from packaged builds

Stat IVSmoke

IVSmoke provides detailed statistics for performance profiling and VRAM monitoring.

Enabling Stats

Open the console (~ key) and type:

stat IVSmoke

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Available Statistics

Memory Stats (GPU VRAM)

Stat Name	Description
Noise Volume	Memory used by the 3D noise texture. Static after generation.
CSM Shadow Maps	Memory used by Cascaded Shadow Maps. Scales with resolution and cascade count.
Per-Frame Textures	Temporary textures allocated each frame (voxel atlas, occupancy, etc.).
Total VRAM	Sum of all IVSmoke GPU memory usage.

Cycle Stats (CPU/GPU Time)

Stat Name	Description
Update Expansion	Time spent in the expansion phase (voxel creation).
Update Sustain	Time spent in the sustain phase (maintenance).
Update Dissipation	Time spent in the dissipation phase (voxel removal).
Process Expansion	Actual voxel creation logic execution time.
Prepare Dissipation	Setup time for dissipation phase.
Process Dissipation	Actual voxel removal logic execution time.

Counter Stats

Stat Name	Description
Active Voxel Count	Current number of active voxels across all volumes.
Created Voxel Count (Per Frame)	Voxels created this frame.
Destroyed Voxel Count (Per Frame)	Voxels removed this frame.

Using with Unreal Insights

For deeper analysis, use Unreal Insights profiler:

Launch with trace=default,ivsmoke
Open Tools > Unreal Insights
Filter by "IVSmoke" to see detailed timing breakdown

Best Practices

Recommended Level Placement

When placing smoke volumes in your level, consider these guidelines:

Spacing and Distribution

Avoid clustering: Do not spawn many smoke volumes in the same location simultaneously. Overlapping volumes in the same area can cause rendering artifacts and significant performance drops.
Stagger activation: If multiple smoke grenades land near each other, consider staggering their activation times slightly.
Use adequate spacing: Maintain reasonable distance between simultaneously active smoke volumes.

Volume Sizing

Match gameplay needs: Size your smoke volumes to cover the intended area without excessive overlap.
Consider sightlines: Place smoke to block key sightlines rather than covering entire areas.

Performance Tips

Limit simultaneous volumes: Keep the number of simultaneously active smoke volumes reasonable for your target hardware.
Use appropriate quality settings: Match quality settings to your target platform.
Test with worst-case scenarios: Test performance with the maximum expected number of simultaneous smoke volumes.