Unity Graphics and Rendering

Unity Graphics and Rendering

Render Pipeline Selection Guide

A render pipeline performs a series of operations that take the contents of a scene and displays them on a screen. Unity provides three render pipelines:

Criteria	Built-in Render Pipeline	Universal Render Pipeline (URP)	High Definition Render Pipeline (HDRP)
Target	Legacy projects	Mobile to high-end consoles/PCs	AAA, automotive, architectural
Customization	Limited	Scriptable, extensible via Renderer Features	Scriptable, Custom Passes, Full Frame Settings
Rendering Paths	Forward, Deferred	Forward, Forward+, Deferred	Forward, Deferred (hybrid tile/cluster)
Shader Authoring	ShaderLab + Surface Shaders	Shader Graph (recommended), HLSL	Shader Graph (recommended), HLSL
SRP Batcher	No	Yes	Yes
Ray Tracing	No	No	Yes (DXR)
Volumetrics	No	No	Yes (fog, clouds)
Anti-Aliasing	MSAA	FXAA, SMAA, TAA, MSAA	FXAA, SMAA, TAA, MSAA
Platforms	All	All (scalable)	High-end (DX11/12, Metal, Vulkan)
GPU Requirement	Standard	Standard	Compute shader capable

Decision flow:

1. Need ray tracing, volumetric clouds, or physically-based sky? --> HDRP
2. Need to target mobile, WebGL, or widest platform range? --> URP
3. Maintaining a legacy project with no migration budget? --> Built-in
4. Starting a new project? --> URP (most projects) or HDRP (high fidelity)

Warning: Render pipelines are NOT interchangeable. Materials, shaders, and post-processing from one pipeline do not work in another without conversion. Upgrading Built-in materials to URP/HDRP requires the pipeline's material upgrader; objects render bright pink if their shader is incompatible.

Source: Render Pipelines

URP (Universal Render Pipeline)

URP is a prebuilt Scriptable Render Pipeline made by Unity for creating optimized graphics across a range of platforms, from mobile to high-end consoles and PCs.

Key features:

• Forward, Forward+, and Deferred rendering paths
• Anti-aliasing: FXAA, SMAA, TAA, MSAA
• 2D Renderer for 2D games
• Renderer Features for custom rendering injection
• SRP Batcher for draw call optimization
• Built-in post-processing via Volume system

See: references/urp-guide.md Source: URP

HDRP (High Definition Render Pipeline)

HDRP is a prebuilt Scriptable Render Pipeline targeting AAA-quality games, automotive demos, and architectural visualization on high-end hardware. It requires compute shader-capable GPUs (DirectX 11/12, Metal, Vulkan).

Key features:

• Physically-based lighting with Physical Light Units
• Material types: Lit, StackLit, Layered Lit, Hair, Fabric, Eye, AxF, Terrain
• Ray tracing: reflections, GI, shadows, AO, subsurface scattering
• Volumetric fog and volumetric clouds
• Physically Based Sky, HDRI Sky, Gradient Sky
• Path tracing with denoising (Optix, Intel Open Image Denoise)
• Water system with caustics and underwater rendering
• Dynamic resolution with DLSS, FSR 1.0, TAA Upscaling

See: references/hdrp-guide.md Source: HDRP

Shader Graph

Shader Graph enables building shaders visually by creating and connecting nodes in a graph framework instead of writing code. Changes are reflected with instant feedback.

Render pipeline compatibility:

Pipeline	Supported
URP	Yes
HDRP	Yes
Built-in Render Pipeline	Yes
Custom SRP	No

Shader Graph is included automatically when you install URP or HDRP.

Custom Function Node -- Inject custom HLSL code into Shader Graphs:

• String mode: Write HLSL directly; use $precision token for half/float
• File mode: Reference external .hlsl files with include guards

// File mode example with include guards
//UNITY_SHADER_NO_UPGRADE
#ifndef MYHLSLINCLUDE_INCLUDED
#define MYHLSLINCLUDE_INCLUDED

void MyFunction_float(float3 A, float B, out float3 Out)
{
    Out = A + B;
}
#endif //MYHLSLINCLUDE_INCLUDED

Pipeline detection in Custom Function nodes:

#ifdef SHADERGRAPH_PREVIEW
    half3 color = half3(0,0,0);
#else
    #if defined(UNIVERSAL_PIPELINE_CORE_INCLUDED)
        half4 shadowCoord = TransformWorldToShadowCoord(WorldPosition);
        Light mainLight = GetMainLight(shadowCoord);
        half3 color = mainLight.color;
    #else
        half3 color = half3(0, 0, 0);
    #endif
#endif

Conditional keywords by pipeline:

• Built-in: BUILTIN_PIPELINE_CORE_INCLUDED
• URP: UNIVERSAL_PIPELINE_CORE_INCLUDED
• HDRP: UNITY_HEADER_HD_INCLUDED
• Preview window: SHADERGRAPH_PREVIEW

See: references/shader-graph.md Source: Shader Graph

Shaders

A shader is a program that runs on the GPU. Unity categorizes shaders into three types:

1. Graphics Pipeline Shaders -- Most common; work with Shader objects to determine scene appearance
2. Compute Shaders -- Perform GPU calculations outside the regular graphics pipeline
3. Ray Tracing Shaders -- Handle ray tracing calculations (HDRP only)

Key terminology:

• Shader Object -- Instance of the Shader class wrapping shader programs and GPU instructions
• ShaderLab -- Unity's language for defining Shader object structure
• Shader Graph -- Visual, code-free shader creation tool
• Shader Asset -- A .shader file defining a Shader object
• HLSL -- High Level Shader Language used inside shader code blocks

Surface Shaders (Built-in pipeline ONLY):

• Streamlined way to write lighting-interactive shaders
• Auto-generates vertex/pixel shaders and rendering passes
• NOT supported in URP or HDRP; use Shader Graph instead

HLSL in ShaderLab:

• Use HLSLPROGRAM directive to add shader code to Pass blocks
• Declare structs connecting shader variables to mesh vertex data
• Use #pragma directives to control compilation
• Support 16-bit precision for mobile optimization

Source: Shaders Introduction

Materials and Textures

Materials and shaders work together to define the appearance of a scene.

Materials

Key workflows:

• Create material assets and assign them to GameObjects
• Modify material properties at runtime via scripting
• Use Material Variants for managing large material collections
• Upgrade Built-in materials to URP/HDRP to prevent pink rendering

Material API -- Key properties and methods:

Property/Method	Purpose
color	Main color of the material
mainTexture	Primary texture
shader	Assigned shader reference
renderQueue	Render order override
enableInstancing	GPU instancing toggle
SetColor(name, color)	Change a color property
SetFloat(name, value)	Set a float property
SetTexture(name, texture)	Assign a texture
SetVector(name, vector)	Set a vector property
SetMatrix(name, matrix)	Set a matrix property
HasProperty(name)	Check if property exists
EnableKeyword(keyword)	Enable a shader keyword
CopyPropertiesFromMaterial(mat)	Copy from another material
Lerp(start, end, t)	Interpolate between materials

Important: Set your desired shader BEFORE modifying properties. Property assignments have no effect if the current shader does not support them.

Textures

Textures are bitmap images applied to mesh surfaces. Key concepts:

• Power-of-two dimensions recommended: 32, 64, 128, 256, 512, 1024, 2048, 4096
• LDR (Low Dynamic Range): PNG, JPG -- values 0.0-1.0
• HDR (High Dynamic Range): EXR, HDR -- extended color ranges
• RGBA: RGB color plus alpha channel for transparency
• Bits per pixel (bpp): Lower values reduce memory and improve GPU cache
• Anisotropic filtering: Improves quality at steep viewing angles

See: references/materials-textures.md Source: Materials, Textures

Cameras

Cameras create an image of a particular viewpoint in a scene, with output displayed on-screen or captured as a texture.

Projection modes:

• Perspective -- Replicates human vision; distant objects appear smaller (default)
• Orthographic -- No perspective; objects render at consistent size regardless of distance; useful for isometric/2D games

Key details:

• At least one camera required per scene
• Multiple cameras supported with configurable render order
• Render path set in Player settings; overridable per camera
• URP and HDRP have pipeline-specific camera documentation
• Orthographic cameras render fog uniformly rather than depth-based

Common camera setups:

• Puzzle games: static camera for full visibility
• FPS: camera parented to player at eye level
• Racing: camera following the vehicle

Source: Cameras

Post-Processing

Post-processing effects simulate physical camera/film properties or enable stylized visuals.

Pipeline	Post-Processing Solution
URP	Built-in (installed with URP template)
HDRP	Built-in (installed with HDRP template)
Built-in	Post-Processing Version 2 package (separate)

Warning: Post-processing solutions are NOT interchangeable across render pipelines. Each pipeline's effects and implementation methods differ.

HDRP anti-aliasing options:

• MSAA -- Most resource-intensive
• TAA -- Motion-dependent temporal smoothing
• SMAA -- Pattern-based edge blending
• FXAA -- Per-pixel; least intensive

HDRP exposure: Histogram-based with percentile selection, metering modes, and pre-exposure for precision with Physical Light Units.

Source: Post-Processing

Render Graph (Unity 6)

The Render Graph system provides a high-level representation of custom SRP render passes, explicitly stating how passes use resources. Both URP and HDRP use Render Graph.

Core Principles

1. Handle-based resources -- Use TextureHandle, BufferHandle, RendererListHandle instead of direct references
2. Scoped access -- Actual resources only accessible inside render pass execution code
3. Explicit declaration -- Each pass declares reads/writes, enabling dependency tracking
4. No persistence -- Resources created within one execution cannot carry to the next
5. RTHandle dependency -- Textures use RTHandle system

Three-Phase Execution (per frame)

1. Setup -- Declare all render passes and resource dependencies
2. Compilation -- System culls unused passes, calculates resource lifetimes for efficient allocation
3. Execution -- Run non-culled passes in declaration order

Key API Pattern -- AddRenderPass

using UnityEngine.Rendering;
using UnityEngine.Rendering.RenderGraphModule;

// 1. Define pass data
class MyPassData { public TextureHandle input, output; public float param; }

// 2. Create and configure pass
using (var builder = renderGraph.AddRenderPass<MyPassData>("MyPass", out var passData))
{
    passData.input = builder.ReadTexture(inputTexture);
    passData.output = builder.UseColorBuffer(
        renderGraph.CreateTexture(new TextureDesc(Vector2.one, true, true)
        { colorFormat = GraphicsFormat.R8G8B8A8_UNorm, name = "Output" }), 0);
    passData.param = 2.5f;

    builder.SetRenderFunc((MyPassData data, RenderGraphContext ctx) =>
    {
        var mpb = ctx.renderGraphPool.GetTempMaterialPropertyBlock();
        mpb.SetTexture("_MainTexture", data.input);
        mpb.SetFloat("_FloatParam", data.param);
        CoreUtils.DrawFullScreen(ctx.cmd, material, mpb);
    });
}

// 3. Lifecycle: new RenderGraph() -> BeginRecording() -> AddPasses -> EndRecordingAndExecute() -> Cleanup()

RenderGraphBuilder Key Methods

Method	Purpose
ReadTexture / WriteTexture	Declare texture read/write dependency
UseColorBuffer / UseDepthBuffer	Write + auto-bind as render/depth target
CreateTransientTexture	Temporary texture scoped to pass
ReadComputeBuffer / WriteComputeBuffer	Declare buffer read/write
UseRendererList	Declare renderer list usage
SetRenderFunc	Set rendering callback
EnableAsyncCompute / AllowPassCulling	Control pass behavior

Resource creation: CreateTexture(), CreateComputeBuffer(), CreateRendererList() Import external: ImportTexture(), ImportBackbuffer(), ImportBuffer()

Source: Render Graph

Rendering Optimization

Draw Call Batching

Batching combines meshes using the same material so Unity renders them with fewer render state updates.

SRP Batcher (URP/HDRP only):

• Reduces CPU time for draw calls by minimizing render-state changes between calls
• Material data persists in GPU memory
• Uses dedicated per-object GPU constant buffer
• For best results: use as few shader variants as possible
• Compatible with URP, HDRP, and custom SRP; NOT Built-in pipeline

Static Batching:

• Merges stationary meshes into unified vertex/index buffers (world-space)
• Each buffer supports up to 64,000 vertices
• Works at build time or runtime
• Only for Mesh Renderers (not Skinned Mesh Renderers)

Dynamic Batching:

• Transforms vertices to world space on CPU at runtime
• Useful for procedurally generated geometry (particles, lines, trails)
• Meshes limited to 900 vertex attributes or 300 vertices
• Not recommended for most uses: CPU overhead may exceed draw call savings
• Not supported in HDRP

GPU Instancing:

• Renders multiple instances of the same mesh in one draw call
• Enable via Material.enableInstancing
• Add per-instance properties (color, transform) via HLSL macros
• Requires shader support with instancing macros

Occlusion Culling

Prevents rendering of GameObjects hidden behind others. Works with frustum culling.

• Baking phase (Editor): Divides scene into cells, generates visibility data
• Runtime: Loads baked data, performs per-camera visibility queries
• Best for: GPU-bound projects with overdraw; small areas separated by solid geometry
• Limitation: Dynamic objects can be occluded but cannot occlude others
• URP/HDRP: Can use GPU occlusion culling instead of CPU-based approach

Source: Draw Call Batching, SRP Batcher

Common Patterns (C#)

Material Property Access at Runtime

// Set shader before modifying properties
material.SetColor("_BaseColor", Color.red);
material.SetFloat("_Smoothness", 0.8f);
material.SetTexture("_BaseMap", myTexture);
if (material.HasProperty("_Metallic"))
    material.SetFloat("_Metallic", 1.0f);
material.EnableKeyword("_EMISSION");

Instance vs Shared Material

Renderer rend = GetComponent<Renderer>();
rend.material.color = Color.blue;        // SAFE: creates per-object instance
// rend.sharedMaterial.color = Color.blue; // DANGEROUS: modifies asset for ALL objects

MaterialPropertyBlock (Per-Object Variation Without Material Instances)

// WARNING: MaterialPropertyBlock BREAKS SRP Batcher compatibility.
// Use only when SRP Batcher is not critical (e.g., Built-in pipeline, few unique objects).
// For SRP Batcher-compatible per-object variation, use GPU Instancing with instance properties
// or create material instances via renderer.material.
private static readonly int BaseColorID = Shader.PropertyToID("_BaseColor");
private MaterialPropertyBlock _propBlock = new MaterialPropertyBlock();

void SetColor(Color color)
{
    Renderer rend = GetComponent<Renderer>();
    rend.GetPropertyBlock(_propBlock);
    _propBlock.SetColor(BaseColorID, color);
    rend.SetPropertyBlock(_propBlock);
}

Anti-Patterns

Anti-Pattern	Problem	Solution
Modifying renderer.sharedMaterial at runtime	Changes the material asset; affects ALL objects using it	Use renderer.material (creates instance) or MaterialPropertyBlock
Creating new Material instances every frame	Memory leak; unbounded allocations	Cache material instances; use MaterialPropertyBlock for per-object variation
Using Surface Shaders in URP/HDRP	Not supported; will fail or render pink	Use Shader Graph or write HLSL shaders
Mixing render pipeline assets	Shaders/materials from wrong pipeline render pink	Use pipeline-specific shaders; run material upgrader when switching
Non-power-of-two texture dimensions	Compression fails; higher memory usage	Use 32, 64, 128, 256, 512, 1024, 2048, 4096
Enabling dynamic batching by default	CPU overhead often exceeds draw call savings	Prefer SRP Batcher (URP/HDRP) or static batching
Too many shader variants	Increased build time, memory, and load time	Strip unused variants; minimize keyword usage
Using Shader.Find() at runtime	Slow; may fail if shader not included in build	Cache shader references; assign in Inspector
Forgetting to call m_RenderGraph.Cleanup()	GPU resource leak	Always cleanup in pipeline Dispose()
Ignoring render queue for transparent objects	Z-fighting, incorrect sort order	Set appropriate renderQueue; sort transparent back-to-front

Key API Quick Reference

Class/Struct	Namespace	Purpose
Material	UnityEngine	Controls shader properties on a renderer
Shader	UnityEngine	References compiled shader programs
Texture2D	UnityEngine	2D texture asset
RenderTexture	UnityEngine	GPU-rendered texture target
Camera	UnityEngine	Scene viewpoint and rendering control
Renderer	UnityEngine	Base class for all renderers
MaterialPropertyBlock	UnityEngine	Per-object shader properties without instancing
CommandBuffer	UnityEngine.Rendering	GPU command list
RenderGraph	UnityEngine.Rendering.RenderGraphModule	Frame render pass management
TextureHandle	UnityEngine.Rendering.RenderGraphModule	Render Graph texture reference
BufferHandle	UnityEngine.Rendering.RenderGraphModule	Render Graph buffer reference
RenderGraphBuilder	UnityEngine.Rendering.RenderGraphModule	Configures individual render passes
CoreUtils	UnityEngine.Rendering	Utility methods (DrawFullScreen, etc.)
Volume	UnityEngine.Rendering	Post-processing/environment effect container
VolumeProfile	UnityEngine.Rendering	Collection of volume effect overrides

Related Skills

• unity-lighting-vfx -- Lighting setup, light types, baking, VFX Graph, particle systems
• unity-platforms -- Platform-specific rendering settings, quality tiers, shader stripping
• unity-2d -- 2D Renderer (URP), sprite rendering, tilemap rendering

Additional Resources

• Render Pipelines Overview
• URP Documentation
• HDRP Documentation
• Shader Introduction
• Shader Graph
• Materials
• Textures
• Cameras
• Post-Processing
• Draw Call Batching
• SRP Batcher
• Occlusion Culling
• Render Graph API (SRP Core 17.0)
• Shader Graph 17.0
• HDRP Features
• Material Scripting API