Best Practices for Shader Graph

GenerativeArt–MadewithUnity
Best Practices for
Shader Graph
2
Charles Sanglimsuwan
Developer Relations Engineer

What we'll cover today
 Motivations
 Demo
 How Shader Graph works
 Choosing the right Master Node
 Optimizations
 Workflow
 What’s next
3

5
Democratize
Development
Solve Hard
Problems
Enable
Success

Brief History
 Early work started in May 2017
 Preview package released in Unity 2018.1
 23 updates since
7

Scriptable Render Pipeline
 Shader Graph requires SRP
 High Definition Render Pipeline (HDRP)
 Lightweight Render Pipeline (LWRP)
 VR Lightweight Render Pipeline (VR LWRP)
9

Shader Generation Process
 Each Render Pipeline has a shader backend
 Shader backends include subshader generators for supported Master
Nodes
 Not all Master Nodes supported by every RP
11

Subshader Generators
 Each Master Node has a per-pipeline template
 Templates have many injection points
 Your Shader Graph is traversed, and injection points are replaced with
node values
 Final outcome is a shader (written in ShaderLab)
12

Properties
Subshader
{
Tags
Pass
{
Material Options
Includes & Defines
Graph Functions
Surface Description Input Struct
Surface Description Output Struct
Surface Description Function
Vertex Input Struct
Vertex Output Struct
Vertex Shader
Fragment Shader
}
}
14
Shader Graph

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Properties
Subshader
{
Tags
Pass
{
Material Options
Includes & Defines
Graph Functions
Vertex Input Struct
Vertex Shader
Fragment Shader
}
}
Shader Graph

16
Properties
Subshader
{
Tags
Pass
{
Material Options
Includes & Defines
Graph Functions
Vertex Input Struct
Vertex Shader
Fragment Shader
}
}
Shader Graph

17
Properties
Subshader
{
Tags
Pass
{
Material Options
Includes & Defines
Graph Functions
Vertex Input Struct
Vertex Shader
Fragment Shader
}
}
Shader Graph

18
void Unity_Multiply_float (float3 A, float3 B, out float3 Out)
{
Out = A * B;
}
struct SurfaceDescriptionInputs
{
float3 WorldSpaceTangent;
}
struct SurfaceDescription
{
float3 Albedo;
}
SurfaceDescription PopulateSurfaceData (SurfaceDescriptionInputs IN)
{
SurfaceDescription surface = (SurfaceDescription)0;
float _Vector1_1EF2E600_Out = 2;
float3 _Multiply_E1E37A64_Out;
Unity_Multiply_float(IN.WorldSpaceTangent,
_Vector1_1EF2E600_Out.xxx,
_Multiply_E1E37A64_Out)
surface.Albedo = _Multiply_E1E37A64_Out;
return surface;
}
Example: Surface Description

19
{
Out = A * B;
}
{
}
{
float3 Albedo;
}
{
return surface;
}

20
{
Out = A * B;
}
{
}
{
float3 Albedo;
}
{
return surface;
}

21
{
Out = A * B;
}
{
}
{
float3 Albedo;
}
{
return surface;
}

22
Properties
Subshader
{
Tags
Pass
{
Material Options
Includes & Defines
Graph Functions
Vertex Input Struct
Vertex Shader
Fragment Shader
}
}
Shader Graph

23
Properties
Subshader
{
Tags
Pass
{
Material Options
Includes & Defines
Graph Functions
Vertex Input Struct
Vertex Shader
Fragment Shader
}
}
Shader Graph

Master Node Overview
25
UnlitHD Lit PBR

PBR Master Node
 Works with all Render Pipelines
 Good starting point for prototyping
 Feature ready for many scenarios
26

HD Lit Master Node
 Compatible only with HDRP
 More features than PBR
 Easy to add needless complexity
27

Unlit Master Node
 Works with all Render Pipelines
 Very lightweight
 Good for effects, vertex modifications
29

Unlit Master Node
Possible to add custom lighting:
1. Create nodes to calculate lighting
from desired shading model (e.g., Blinn-Phong)
2. Connect output color to the Color port
30

Master Node Review
 PBR is the most versatile node
 Use HD Lit only when applicable and necessary
 Consider Unlit for particle effects, UI, etc.
31

Built-in Optimizations
1. Where ever possible, Shader Graph will not add unused features to
output shader
 Changing the default value will mark the feature active
 Connecting any node will mark the feature active
2. The shader compiler will compile out no-op features
33

Optimization Example: Coat Mask
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No CoatMask code will be present in the output
ShaderLab code if the value is zero

Optimization Example: Metallic
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If the Metallic is set to zero, that code block will
be compiled out by the shader compiler

Optimization Example: Emission
36
If the Emission is set to Black, and disabled in
Material, that code block will be compiled out by
the shader compiler

Built-in Optimizations
1. Where ever possible, Shader Graph will not add unused features to
output shader
 Changing the default value will mark the feature active
 Connecting any node will mark the feature active
2. The shader compiler will compile out no-op features
37

Draw Call Batching
 GPU instancing is supported in shaders
 Needs to be enabled on the material
 Requires hardware support
 All generated shaders are compatible with the SRP Batcher (2018.3)
38

SRP Batcher
 New batching solution, designed for SRP
 Improved rendering performance
 Works with SkinnedMeshRenderers!
 Requires per-material parameters to be stored in a constant buffer
40

Render Faster with the SRP Batcher
41
0
5
10
15
20
25
30
35
Scene: 1024 materials Scene: 1 material
RenderTime(ms)
5.26x Faster 1.27x Faster
SRP
Legacy
Lower is better

Node Decimation
 Eliminate no-op nodes
 Bake values back into the textures
 Examples: gradients, noise
 Combine nodes when possible
43

Example: Texture Modification
44

Data Formats
 Each node has a memory cost
 Use smaller data structures when possible
 Modifying precision
 Requires code modification
49

50
public enum OutputPrecision
{
@fixed,
@half,
@float
}
private OutputPrecision m_OutputPrecision = OutputPrecision.@float;
Modifying Precision
AbstractMaterialNode.cs

Reduce Math Operations
 Multiply scalar values before vector values
 Prefer blending results, instead of branching
 Research impact of certain math operations
 Prefer constants when possible
51

Example: Reciprocal
52
Fast mode requires Shader Model 5

Reduce Math Operations
 Multiply scalar values before vector values
 Prefer blending results, instead of branching
 Research impact of certain math operations
 Prefer constants when possible
53

Workflow: Manual Optimizations
 Hand-optimizing shaders is a one-way path
 Don’t manually optimize too early
 Copy or view shader code in Master Node menu
55

Workflow: Manual Optimizations
56

Workflow: Faster Iterations
 Nodes not connected to Master Node aren’t evaluated
 Can keep them in view for quick iterations
 Create a Preview node that isn’t attached to the Master Node
 Editing these nodes will be much faster
57

Workflow Summary
1. Prototype with PBR Master Node
 Move to HD Lit if necessary
2. Start optimization
1. Optimize nodes
2. Convert properties to inline values
3. Near the end of the project, start hand optimizing shaders
58

Custom API
 Create your own nodes
 Examples: specialized noise functions, custom lighting, etc.
 Full documentation available on GitHub
60

Vertex Modification
 Low-impact on CPU performance
 Good for animating foliage, water, or cloth
61

Roadmap
2019.1
 First official, verified release
 Completely overhauled Node API
 Key bug fixes, UX improvements
65

Available Resources
 Plentiful samples abound:
 Andy Touch
 Keijiro Takahashi
 Video tutorials on YouTube
 Source available on GitHub
66

Best Practices for Shader Graph

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