Unity Shaders and Rendering Skill

Unity Shaders and Rendering

Overview

Reference for Unity's rendering systems, shader development, lighting configuration, and visual effects. Covers all three render pipelines, Shader Graph, hand-written shaders, and VFX Graph.

Render Pipeline Comparison

| Feature | Built-in RP | URP | HDRP | |---------|------------|-----|------| | Target | Legacy projects | Mobile, VR, wide range | High-end PC/console | | Shader language | Surface shaders + HLSL | HLSL (no surface shaders) | HLSL | | Shader Graph | Yes | Yes | Yes | | SRP Batcher | No | Yes | Yes | | Render Features | No | Yes (ScriptableRendererFeature) | Custom Pass | | Post-processing | Post Processing Stack v2 | Volume system (built-in) | Volume system (built-in) | | Ray tracing | No | No (probe-based) | Yes (DXR) | | Performance | Moderate | Optimized for scale | Highest fidelity |

Recommendation: Use URP for new projects unless targeting high-end visuals exclusively (HDRP). Built-in RP is legacy -- migrate when possible.

Shader Graph

Getting Started

Right-click in Project: Create > Shader Graph > URP > Lit Shader Graph
Double-click to open Shader Graph editor
Build node network connecting to Master Stack outputs
Create a Material using the shader, assign to renderers

Master Stack Outputs (URP Lit)

| Output | Type | Purpose | |--------|------|---------| | Base Color | Color (RGB) | Albedo/diffuse color | | Normal | Vector3 | Tangent-space normal map | | Metallic | Float (0-1) | Metal vs. dielectric | | Smoothness | Float (0-1) | Roughness inverse | | Emission | Color (RGB) | Self-illumination | | Alpha | Float (0-1) | Transparency | | Alpha Clip Threshold | Float | Cutoff for alpha testing |

Common Node Patterns

| Effect | Key Nodes | |--------|-----------| | Dissolve | Noise > Step > Alpha Clip + Edge emission | | Scrolling UV | Time > Multiply > Add to UV | | Fresnel glow | Fresnel Effect > Multiply color > Emission | | Triplanar mapping | Triplanar node (avoids UV stretching) | | Color shift | Lerp between colors using parameter or time | | Vertex displacement | Noise > Multiply > Add to Position | | Outline | Two-pass: inverted hull in custom render feature |

Shader Graph Sub Graphs

Extract reusable node groups into Sub Graphs (Create > Shader Graph > Sub Graph). Use for shared noise functions, UV transformations, or custom lighting models.

Hand-Written Shaders (ShaderLab + HLSL)

URP Shader Structure

Shader "Custom/SimpleUnlit"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Color ("Color", Color) = (1,1,1,1)
    }

    SubShader
    {
        Tags { "RenderType"="Opaque" "RenderPipeline"="UniversalPipeline" }

        Pass
        {
            HLSLPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

            struct Attributes
            {
                float4 positionOS : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct Varyings
            {
                float4 positionHCS : SV_POSITION;
                float2 uv : TEXCOORD0;
            };

            TEXTURE2D(_MainTex);
            SAMPLER(sampler_MainTex);

            CBUFFER_START(UnityPerMaterial)
                float4 _MainTex_ST;
                half4 _Color;
            CBUFFER_END

            Varyings vert(Attributes IN)
            {
                Varyings OUT;
                OUT.positionHCS = TransformObjectToHClip(IN.positionOS.xyz);
                OUT.uv = TRANSFORM_TEX(IN.uv, _MainTex);
                return OUT;
            }

            half4 frag(Varyings IN) : SV_Target
            {
                half4 tex = SAMPLE_TEXTURE2D(_MainTex, sampler_MainTex, IN.uv);
                return tex * _Color;
            }
            ENDHLSL
        }
    }
}

Key differences from Built-in shaders:

Use HLSLPROGRAM/ENDHLSL (not CGPROGRAM/ENDCG)
Include URP shader library, not UnityCG.cginc
Use TEXTURE2D/SAMPLER macros (not sampler2D)
Wrap properties in CBUFFER_START(UnityPerMaterial) for SRP Batcher compatibility

Lighting

Light Types

| Type | Use For | Shadow Cost | |------|---------|-------------| | Directional | Sun, global illumination | Low (cascaded shadow maps) | | Point | Torches, lamps | Medium | | Spot | Flashlights, stage lights | Medium | | Area (baked only) | Soft window light, panels | High (bake only) |

Lighting Modes

| Mode | Description | Best For | |------|-------------|----------| | Realtime | Computed every frame | Dynamic objects, few lights | | Baked | Pre-computed into lightmaps | Static environments | | Mixed | Baked indirect + realtime direct | Best balance |

Lightmap Baking Tips

Set lightmap resolution based on scene scale (10-40 texels/unit for indoor)
Use Light Probes for dynamic objects in baked scenes
Use Reflection Probes for metallic/reflective surfaces
Enable GPU Lightmapper for faster bake times
Mark objects as Contribute GI in the Static flags

Post-Processing (Volume System)

Setup:
1. Add a Volume (Global or Local) to the scene
2. Create a Volume Profile asset
3. Add overrides: Bloom, Color Adjustments, Tonemapping, etc.
4. Camera must have Post Processing enabled (URP Camera settings)

| Effect | Performance | Notes | |--------|-------------|-------| | Bloom | Low | Use threshold to control intensity | | Color Adjustments | Very Low | Saturation, contrast, color filter | | Tonemapping | Very Low | ACES for cinematic look | | Vignette | Very Low | Frame darkening | | Ambient Occlusion (SSAO) | Medium | Disable on mobile | | Depth of Field | High | Use Bokeh only for cinematics | | Motion Blur | Medium | Can cause motion sickness in VR |

VFX Graph vs Particle System

| Feature | Particle System (Shuriken) | VFX Graph | |---------|---------------------------|-----------| | Execution | CPU | GPU (compute shader) | | Particle count | Thousands | Millions | | Complexity | Component-based, simple | Node-based, complex | | Platform | All | Compute shader capable only | | Integration | Physics, collision | Limited physics |

Use Particle System for gameplay-integrated effects (physics collisions, small counts). Use VFX Graph for visual spectacles (rain, fire, magic, ambient particles).

URP Render Features

Extend URP rendering with custom ScriptableRendererFeatures:

public class OutlineFeature : ScriptableRendererFeature
{
    OutlinePass _pass;

    public override void Create()
    {
        _pass = new OutlinePass();
        _pass.renderPassEvent = RenderPassEvent.AfterRenderingOpaques;
    }

    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData data)
    {
        renderer.EnqueuePass(_pass);
    }
}

Common uses: custom outlines, screen-space effects, render texture generation, stencil-based effects.

Additional Resources

Reference Files

references/shader-recipes.md -- Complete shader implementations: toon/cel shading, water, dissolve, hologram, force field, procedural skybox, stencil portal, vertex animation, custom lighting models
references/lighting-vfx-detail.md -- Advanced lighting setups, GI troubleshooting, VFX Graph cookbook (fire, smoke, electricity, portals), Scriptable Render Pipeline customization, custom render passes

Agent Skills: Unity Shaders and Rendering

Install this agent skill to your local

Skill Files