Material Editor UI

https://docs.unrealengine.com/en-us/Engine/Rendering/Materials/Editor/Interface

Hotkeys (Hold key + mouse left click)
Hotkey Expression
A Add
B BumpOffset
C Comment
D Divide
E Power
F MaterialFunctionCall
I If
L LinearInterpolate
M Multiply
N Normalize
O OneMinus
P Panner
R ReflectionVector
S ScalarParameter
T TextureSample
U TexCoord
V VectorParameter
1 Constant
2 Constant2Vector
3 Constant3Vector
4 Constant4Vector
Shift + C ComponentMask
How to Make Material Attributes

Max Material Texture Samplers

By default: Using OpenGLES2.0 you can use 8 samplers(You are only allowed to use 5 texture samplers due to hardware limitations.), using OpenGLES3.1 or DirectX you can use 16 samplers.

Using Shared samplers in DirectX 11 you can use up to 128 samplers.

Origin:

In version 4.6 and up using DirectX 11 you can use up to 128 samplers by changing the sampler to a “Shared Sampler”. Click on the texture sample and then choose from the details panel either “Wrap” or “Clamp”. It is usually Wrap but to double check open the texture to see which format it uses.

Otherwise you are limited to 16 samplers, with some being used by the rendering engine by default. I have an ocean material that uses 10 of the default 16 without any textures present, it depends on the type of material (translucent, opaque, TLM_Surface etc.). If you are creating a mobile material it is even lower, just 6.

Reference:
Max Material Texture Samples?
https://forums.unrealengine.com/development-discussion/rendering/33339-max-material-texture-samples
Shared samplers
https://answers.unrealengine.com/questions/785500/shared-samplers.html

Offical Docs

Materials for Mobile Platforms
https://docs.unrealengine.com/en-US/Platforms/Mobile/Materials/index.html

Textures for Mobile Platforms
https://docs.unrealengine.com/en-US/Platforms/Mobile/Textures/index.html

Material Analyzer
https://docs.unrealengine.com/en-US/Engine/Rendering/Materials/MaterialAnalyzer/index.html

Shading Models
https://docs.unrealengine.com/en-US/Engine/Rendering/Materials/MaterialProperties/LightingModels/index.html

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