Hi,
In Unity 6.6 (6000.6.0a5), we’re adding Preprocessor Directives to Shader Graph, allowing you to add Pragmas, Defines and Includes to the shader without relying on Custom Function Nodes.
Preprocessor Directives
The Preprocessor Directives can be found at the bottom of the Graph Settings.
Pragmas
Pragmas can now be added to shader graphs. This allows you to add pragma directives such as:
enable_debug_symbols, which generates shader debug symbols.use_dxc, which makes the shader compile with the DXC compiler.intancing_options procedural:functionName, which enables procedural instancing with the supplied function.
To learn more about pragmas, see HLSL pragma directives reference.
Defines
Custom Defines can be set so as to allow for constant branching or provide local constant values.
Examples:
_DEBUG // temporarily switch between branches_MAX_ITERATIONS 16 // set the maximum number of iterations for a loop in a Custom Function Node
The expected format is:
NAME VALUE (optional) // Comments (optional)
Where:
- NAME is the name of the #define.
- VALUE is usually a number (but can be anything to replace occurrences of NAME with).
- // Comments must be put behind double slashes.
Toggle
If the define is just a name like _DEBUG, you can:
- Use it in a Custom Function with #ifdef, #ifndef, #if defined(_DEBUG) for static branching.
- Use a Custom Function Node to fetch the state in the shader graph.
- Or use a Predefined Keyword.
Predefined Keywords use predefined constants.
#ifdef _DEBUG
Out = true;
#else
Out = false;
#endif
Constant Value
If the define is a constant value, like MAX_ITERATIONS 16, you should declare a default value in the Custom Function like this:
#ifndef MAX_ITERATIONS
#define MAX_ITERATIONS 16
#endif
float CustomNoise(float2 uv)
{
[unroll]
for (int i = 0; i < MAX_ITERATION; i++)
{
// recursive noise
}
}
Overriding Hierarchy
Since graph defines are set before includes and custom function code, their definition prevails.
Although they can be overridden with Shader Constant Defines in Project Settings / Graphics and/or Build Profiles Graphics Settings, which are also new in Unity 6.6.
Note: Shader Constant Defines in Graphics settings only allow for name/value pairs. If you want to override a name such as _DEBUG, you may just set a dummy value like _DEBUG 1.
But then you should use a Custom Function Node to branch, as Predefined Keywords expect no value.
#ifdef _DEBUG
Out = _DEBUG == 1;
#else
Out = false;
#endif
Includes
Shader Includes (HLSL files) can now be included without using a Custom Function Node.
This is useful to reference an include that contains some definitions that need to be included before others referenced by Custom Function Nodes.
