HLSL / Cg Syntax

A quick primer on the HLSL syntax supported in unity.

Data types

• bool - true or false.
• int - 32-bit signed integer.
• uint - 32-bit unsigned integer.
• half - 16-bit floating point value.
• float - 32-bit floating point value.
• double - 64-bit floating point value.
• void - No value.

Variables

Normal variables are definied by type name = value;.

float depth = _Amount * info;

Vectors

Vectors are arrays of values, in the form typeN where N is the same.

float3 rgb = tex2D(_MainTex, uv).rgb;

Functions

Functions always take the form return_type name(args, ...) { ... }.

float calc(float a, float b) { return a * b; }

Notce that unlike C, function overloading is supported in HLSL.

Structs

Structs allow data to be passed around under a single pointer.

The basic syntax for a struct is struct Name { type name1; type name2; ... }.

struct Input {
    float2 uv_MainTex;
};

Notice that unlike C structs in HLSL automatically generate a typedef. That is, an instance of Input is passed as Input foo not struct Input Foo.

Unlike C, the naming of fields in structs is highly significant in Unity. In the example above, uv_MainTex is populated by the uv coordinate of the _MainTex property:

  Properties {
    _MainTex ("Texture", 2D) = "white" {}
  }

If the name is incorrect, the values will not be populated.

#define, macros etc.

As with C, the following statements are generally supported:

#define
#ifdef
#ifndef
#else
#endif

Unity supports all the basic functionality of these operators.

#define FOO 2
#ifdef FOO
  #if FOO == 1
    #define ADD(x,y) x + y * 2.0
  #endif
  #if FOO == 2
    #define ADD(x,y) x + y * 4.0
  #endif
#endif
#ifndef ADD
  #define ADD(x, y) x
#endif