.HLSL

Introduction

HLSL, the High-Level Shader Language, is Microsoft’s C-like language for shaders in Direct3D. It is compiled ahead of time to a compiled shader object, which the program hands to the graphics driver. Microsoft’s newer compiler can also produce SPIR-V, so HLSL is used for Vulkan as well, and many game engines write their shaders in it.

Shader source is usually named .hlsl, with shared code in .hlsli include files. .fx files are HLSL effects, an older form that groups shaders and render states into techniques and passes.

Structure

An HLSL file is plain text, with C-style functions, structs and a preprocessor. Inputs and outputs are marked with semantics after a colon, such as POSITION, TEXCOORD0 or the system values SV_Position and SV_Target. Constants from the program come in constant buffers declared with cbuffer, and textures and samplers are bound to numbered registers. One file can hold several entry points; the compiler is told which one to compile and for which shader model, such as vs_5_0 or ps_6_0.

struct PSInput {
    float4 position : SV_Position;
    float4 colour   : COLOR;
};

float4 PSMain(PSInput input) : SV_Target {
    return input.colour;
}

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