Unity Lighting Vfx

Unity Lighting and Visual Effects

Lighting Modes

Unity provides three light modes controlling how illumination is calculated.

Realtime Lights

• Calculate lighting every frame at runtime
• Allow dynamic changes to intensity, color, position
• Cast shadows up to Shadow Distance
• Contribute only direct lighting by default (no bounced light)
• Higher runtime cost, especially in complex scenes or low-end hardware
• Best for: dynamic objects, flickering effects, moving light sources

Baked Lights

• Calculations performed in the Unity Editor and saved as lighting data to disk
• At runtime, Unity loads pre-computed data instead of calculating dynamically
• Bake both direct and indirect lighting into lightmaps
• Store information in Light Probes for moving objects
• Cannot modify light properties at runtime; do not illuminate dynamic GameObjects
• No specular contributions
• Best for: static scenery, complex indirect lighting, performance-critical scenarios

Mixed Lights

• Combine baked indirect lighting with real-time direct lighting
• Behavior depends on the Lighting Mode setting in the Lighting window
• Cast real-time shadows (not baked soft shadows)
• Can change properties at runtime (affects real-time component only)
• Always more expensive than fully baked lighting
• Best for: dynamic shadows with baked background lighting

Important: All baked/mixed modes require Baked Global Illumination enabled. Without it, Mixed and Baked lights behave as Realtime.

Light Types

Directional Light

• Located infinitely far away, emits light in one direction
• Parallel rays, no distance-based intensity falloff
• Simulates sun/moon; every new scene includes one by default
• Links to procedural sky system; rotate to create time-of-day effects

Point Light

• Located at a point, emits in all directions equally
• Intensity follows inverse square law (diminishes with distance squared)
• Use for lamps, explosions, local illumination

Spot Light

• Located at a point, emits in a cone shape
• Adjustable cone angle; light diminishes at edges (penumbra)
• Wider angles create larger fade areas
• Use for flashlights, headlights, searchlights

Area Light

• Defined by a rectangle or disc; emits uniformly across surface
• Follows inverse square law; produces soft, subtle shading
• Bake-only -- not available at runtime
• Use for street lights, realistic interior lighting

Global Illumination

Global illumination (GI) simulates how light bounces between surfaces, producing realistic indirect lighting.

Baked GI

• Pre-computes indirect lighting into lightmaps using the Progressive Lightmapper (CPU or GPU)
• Results stored in lightmap textures and Light Probes
• Configure in the Lighting window under Bake settings
• GPU Progressive Lightmapper offers faster bake times with configurable tile sizes

Environment Lighting

Three ambient light sources configured in the Lighting window Environment tab:

• Skybox: Uses skybox material colors for ambient light from different angles
• Gradient: Separate sky, horizon, and ground colors with smooth blending
• Color: Uniform ambient light across the scene

Intensity Multiplier (0-8, default 1) controls ambient brightness.

Environment Reflections

• Source: Skybox or custom Cubemap/RenderTexture
• Configurable resolution, compression, intensity multiplier
• Bounces setting controls reflection evaluation iterations between objects

Light Probes and Adaptive Probe Volumes

Light Probes

• Capture lighting information in empty space throughout a scene
• At runtime, indirect lighting for dynamic GameObjects is approximated using nearest probes
• Provide indirect bounced light for moving objects and LOD system support
• Must be manually placed using Light Probe Groups
• Store baked lighting information; work with both direct and indirect lighting

Adaptive Probe Volumes (APV)

APV is the modern replacement for manual Light Probe placement in URP:

• Automated probe placement -- eliminates manual Light Probe Group positioning
• Per-pixel lighting -- superior quality compared to per-object approaches
• Scene baking -- bake multiple scenes together using Baking Sets
• Runtime adjustments -- Lighting Scenarios and sky occlusion for dynamic changes
• Large-world support -- streaming data for expansive open-world environments
• Data flexibility -- loading from AssetBundles or Addressables
• Configurable probe density and volume size with visualization tools

Reflection Probes

Capture a spherical view of surroundings as a cubemap for reflective materials.

Types

Key Properties

• Importance: Rendering priority when multiple probes overlap
• Intensity: Texture brightness in shader calculations
• Box Projection: Enables projection mapping for interiors (requires URP config)
• Box Size/Offset: World-space bounding box for reflection contribution
• Blend Distance: Blending distance for deferred probes

Realtime Options

• Refresh Mode: On Awake, Every Frame, or Via Scripting
• Time Slicing: All Faces At Once, Individual Faces, No Time Slicing

Particle System vs VFX Graph

Decision Guide:

• Use Particle System for mobile targets, simple effects, when you need full CPU-side scripting control, or when targeting the Built-in Render Pipeline
• Use VFX Graph for massive particle counts, GPU-driven simulations, complex node-based authoring, or high-end platforms with URP/HDRP

Particle System Modules

VFX Graph Basics

Systems

1. Spawn System: Single Spawn Context managing emission
2. Particle System: Initialize -> Update -> Output succession
3. Mesh Output System: Single Mesh Output Context

Contexts

• Spawn: Executes each frame to calculate spawn amounts. States: Running, Idle, Waiting. Configurable loop duration, count, and delays
• Initialize: Runs at particle birth, sets initial state. Processes Blocks for newly spawned particles. Configurable bounds and capacity
• Update: Per-frame for all living particles. Automatic: position integration, rotation integration, aging, reaping
• Output: Renders particles (Quad, Mesh, etc.). No output ports. Customizable rendering blocks

Graph Elements

• Blocks: Stackable nodes within Contexts; each handles one operation; top-to-bottom execution
• Operators: Low-level property workflow nodes connecting to Block/Context ports
• Properties: Connectable via property workflow
• Settings: Non-connectable editable values per Context

GPU Events

Experimental feature where GPU computes events (vs CPU for normal events). Cannot be customized with Blocks.

Common Patterns (C#)

Create and Configure a Light

using UnityEngine;

public class LightSetup : MonoBehaviour
{
    void Start()
    {
        GameObject lightObj = new GameObject("Dynamic Light");
        Light light = lightObj.AddComponent<Light>();
        light.type = LightType.Point;
        light.color = Color.yellow;
        light.intensity = 2.0f;
        light.range = 15f;
        light.shadows = LightShadows.Soft;
        light.shadowResolution = UnityEngine.Rendering.LightShadowResolution.Medium;
    }
}

Create a Realtime Reflection Probe

using UnityEngine;
using UnityEngine.Rendering;

public class ProbeSetup : MonoBehaviour
{
    void Start()
    {
        GameObject probeObj = new GameObject("Realtime Reflection Probe");
        ReflectionProbe probe = probeObj.AddComponent<ReflectionProbe>();
        probe.size = new Vector3(10, 10, 10);
        probe.mode = ReflectionProbeMode.Realtime;
        probe.refreshMode = ReflectionProbeRefreshMode.EveryFrame;
        probe.resolution = 256;
        probe.hdr = true;
    }
}

Control Particle System at Runtime

using UnityEngine;

public class ParticleController : MonoBehaviour
{
    ParticleSystem ps;

    void Start()
    {
        ps = GetComponent<ParticleSystem>();

        // Modify emission rate -- cache module in local variable first
        var emission = ps.emission;
        emission.rateOverTimeMultiplier = 50f;

        // Modify main module
        var main = ps.main;
        main.startLifetime = 3f;
        main.startSpeed = 5f;
        main.simulationSpace = ParticleSystemSimulationSpace.World;
    }

    void OnTriggerEnter(Collider other)
    {
        // Burst emit particles
        ps.Emit(100);
    }

    void OnDisable()
    {
        ps.Stop(true, ParticleSystemStopBehavior.StopEmittingAndClear);
    }
}

VFX Graph Runtime Control

using UnityEngine;
using UnityEngine.VFX;

public class VFXController : MonoBehaviour
{
    VisualEffect vfx;
    VFXEventAttribute eventAttr;

    void Start()
    {
        vfx = GetComponent<VisualEffect>();
        eventAttr = vfx.CreateVFXEventAttribute();

        // Set exposed properties
        vfx.SetFloat("SpawnRate", 100f);
        vfx.SetVector3("Direction", Vector3.up);
        vfx.playRate = 1.5f;
    }

    void OnTriggerEnter(Collider other)
    {
        // Send custom event with attributes
        eventAttr.SetVector3("position", other.transform.position);
        vfx.SendEvent("OnHit", eventAttr);
    }

    public void StopEffect()
    {
        vfx.Stop();
    }
}

Refresh Reflection Probe on Demand

using UnityEngine;

public class ProbeRefresher : MonoBehaviour
{
    ReflectionProbe probe;

    void Start()
    {
        probe = GetComponent<ReflectionProbe>();
        probe.refreshMode = UnityEngine.Rendering.ReflectionProbeRefreshMode.ViaScripting;
    }

    public void RefreshReflections()
    {
        probe.RenderProbe();
    }

    public bool IsReady()
    {
        return probe.IsFinishedRendering(probe.RenderProbe());
    }
}

Anti-Patterns

Lighting Anti-Patterns

1. Too many Realtime lights: Each realtime light adds per-frame cost. Use Baked or Mixed for static lights
2. Forgetting to enable Baked Global Illumination: Mixed/Baked lights silently fall back to Realtime without it
3. Overlapping Reflection Probes without Importance values: Causes flickering; always set Importance to establish priority
4. Using Area Lights expecting runtime behavior: Area lights are bake-only; they produce no light at runtime
5. Ignoring Indirect Multiplier: Leaving at default can cause over-bright or too-dark bounced light; tune per light
6. Not setting Shadow Bias correctly: Too low causes self-shadowing artifacts (shadow acne); too high causes peter-panning (shadows detach from objects)
7. Manual Light Probe placement in large scenes: Use Adaptive Probe Volumes (APV) in URP instead for automated, per-pixel quality

Particle System Anti-Patterns

1. Not caching module references: Each property access on a module struct immediately writes to native code; cache the module variable
2. Using World simulation space for attached effects: Particles drift away from moving parents; use Local space for attached FX
3. Excessive particle counts on CPU: Particle System is CPU-bound; for >10K particles, consider VFX Graph
4. Forgetting to Stop/Clear: Leaked particle systems consume CPU even when invisible

VFX Graph Anti-Patterns

1. Using VFX Graph for simple effects on mobile: GPU overhead and URP/HDRP requirement make it overkill for simple mobile effects
2. Not setting Capacity in Initialize: Default capacity may allocate too much or too little GPU memory
3. Ignoring Bounds: Incorrect bounds cause effects to be culled when visible; always configure bounds in Initialize context
4. Sending events every frame without throttling: SendEvent has CPU-GPU sync cost; batch or throttle event dispatch

Key API Quick Reference

Light (UnityEngine.Light)

ParticleSystem (UnityEngine.ParticleSystem)

VisualEffect (UnityEngine.VFX.VisualEffect)

ReflectionProbe (UnityEngine.ReflectionProbe)

Related Skills

• unity-graphics -- Render pipelines (URP/HDRP/Built-in), shaders, materials, cameras
• unity-2d -- 2D lighting (URP 2D Renderer), sprite rendering
• unity-platforms -- Platform-specific lighting quality tiers, mobile optimization

Additional Resources

• Lighting Overview
• Light Types
• Light Modes
• Light Probes
• Reflection Probes
• Adaptive Probe Volumes (URP)
• Particle System Modules
• VFX Graph Package
• Light Scripting API
• ParticleSystem Scripting API
• ReflectionProbe Scripting API