Preprocessor Specifications

HCSL supports the following preprocessor directives.

#version

Specifies the shader version. Write this at the top of the file. Currently, only version "1" is supported.

#version 1

#define

Used for macro definitions. You can also define macros with values or function-like macros.
It can only be written inside a shader block.

shader vertex
{
    #define PI 3.1415
    #define rot(a) mat2(cos(a), -sin(a), sin(a), cos(a))

    // Directly write a shader variant (Writing this inside the variant block is more versatile)
    #define _RED

    void main()
    {
        vec4 pos = vec4(_Position, 1.0);

        float angle = PI * 0.5;
        pos.xy *= rot(angle);

        #ifdef _RED
        col = vec4(1.0, 0.0, 0.0, 1.0);
        #else
        col = vec4(1.0, 1.0, 1.0, 1.0);
        #endif

        outPos = HEL_MATRIX_P * HEL_MATRIX_V * HEL_MATRIX_W * pos;
    }
}

#pragma

Preprocessor for changing behavior during compilation.

pass Geometry_Opaque
{
    #pragma hcsl_enabled_extension normal_shadowmap // Enable shadow map extension

    attribute
    //...
}

List of pragma Directives

Preprocessor	Description
`#pragma hcsl_enabled_extension normal_shadowmap`	Outputs the code necessary for standard shadow mapping.
`#pragma hcsl_enabled_extension instance_data_map`	Outputs the code necessary for instance data mapping (for instanced rendering).
`#pragma hcsl_enabled_extension skinmesh_animation`	Outputs the code necessary for skin mesh animation.

#include

Preprocessor directive used to include HCSLLib.

It can only be used inside the shader block.

For more details on HCSLLib, please refer to HCSLLib.

shader fragment
{
    // Include to use the helRand function
    // helRand is defined in another file named TestLib
    #include "TestLib"

    // Include to use the helCalcUVTransform function
    // HCSLCore/Texture is a built-in library
    #include "HCSLCore/Texture"

    void main()
    {
        vec2 st = helCalcUVTransform(uv, _MainTex_ST);
        vec4 col = helTexture(_MainTex, st) * helRand(vec2(0.5));

        outColor = col;
    }
}

Preprocessors Supported by Variant Block

With the introduction of the variant block (variant), the following preprocessor directives are now supported for conditional compilation.

#ifdef
#ifndef
#if
#elif
#else
#endif

These can be used to enable or disable parts of the shader code based on conditions defined by the variant block or macros defined with #define.

For detailed usage of the variant block, please refer to here.

Example Usage

variant
{
    int _RED = 1;
    int _GREEN = 1;
    int _BLUE = 0;
    int _ALPHA = 1;
}

shader fragment
{
    void main()
    {
        vec4 col = vec4(1.0);

        // When a single macro is defined
        #ifdef _RED
        col = vec4(1.0, 0.0, 0.0, 1.0);
        #endif

        // When a macro is not defined
        #ifndef _BLUE
        col *= 0.5;
        #endif

        // Complex conditional statements
        #if defined(_GREEN) && defined(_ALPHA)
        col.a = 0.8;
        #elif defined(_GREEN)
        col.a = 0.5;
        #else
        col.a = 1.0;
        #endif

        // Combination of multiple conditions
        #if defined(_RED) || defined(_BLUE)
        col.rgb += 0.2;
        #endif

        outColor = col;
    }
}

Writing Conditional Expressions

In #if and #elif, you can use defined(MACRO) to determine whether a macro is defined.
You can combine multiple conditions using || (logical OR), && (logical AND), ! (negation), etc.
Grouping with parentheses is also possible.

Examples of Conditional Expressions

#if defined(_RED)
// When _RED is defined

#elif defined(_GREEN) && defined(_ALPHA)
// When both _GREEN and _ALPHA are defined

#elif defined(_BLUE) || defined(_ALPHA)
// When either _BLUE or _ALPHA is defined

#elif !(defined(_RED) || defined(_GREEN))
// When neither _RED nor _GREEN are defined

#else
// When none of the above are matched
#endif

Notes

Conditional statements can be written with a syntax akin to the C language preprocessor.
Macros defined in the variant block can also be used in #if and #ifdef.

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