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Bare-bones material graph evaluation via Compute Shader in UE5

This template provides an example of linking a custom compute shader to any material defined in the editor. Allowing you to input/output parameters from material graphs defined by developers or artists.

Get the code

$ shadeup-unreal
 > [COMPUTE] Compute Shader
 > Base with material

Applications

• Drive indirect instancing from a texture sampled in a material graph.
• Sample and find the average color of a material on the GPU.
• Generate & derive height-maps/normals using user-defined graphs.

This workflow opens up a world of possibilities and is one of the coolest features of the Unreal shader pipeline.

Usage

1. Generate or download the template using the instructions above
2. Rebuild your project
3. Create or navigate to an existing Blueprint
4. Right-click and add the node called “Execute Base Material Compute Shader”

Helpful reading

• Render Dependency Graph

Sample snippet

// basemat.usf

#include "/Engine/Generated/Material.ush"
#include "/Engine/Public/Platform.ush"

float2 Position;
RWBuffer<float4> OutputColor;

[numthreads(THREADS_X, THREADS_Y, THREADS_Z)]
void BaseMatExample(
	uint3 DispatchThreadId : SV_DispatchThreadID,
	uint GroupIndex : SV_GroupIndex )
{
	float4 SvPosition = float4(Position.xy, 0, 0);

	FMaterialPixelParameters MaterialParameters = MakeInitializedMaterialPixelParameters();

	// There are various inputs we can provide to the material graph via FMaterialPixelParameters
	// See: https://github.com/EpicGames/UnrealEngine/blob/5.0/Engine/Shaders/Private/MaterialTemplate.ush#L262

	MaterialParameters.VertexColor = half4(1, 1, 0, 1);

	FPixelMaterialInputs PixelMaterialInputs = (FPixelMaterialInputs)0;

	// This is the call to the material graph
	CalcMaterialParameters(MaterialParameters, PixelMaterialInputs, SvPosition, true);

	// PixelMaterialInputs is a struct that contains the outputs of the material graph
	// Use the provided helper methods ( GetMaterialXYZ(...) ) to access the outputs
	// See: https://github.com/EpicGames/UnrealEngine/blob/5.0/Engine/Shaders/Private/MaterialTemplate.ush#L2485

	OutputColor[0] = float4(GetMaterialBaseColor(PixelMaterialInputs), 0);

	// You can also access custom output nodes via their respective names
	// e.g. GetMyCustomMaterialOutput0(MaterialParameters)
	// See: Custom node example
}