Built-in macros

Unity defines several preprocessor macros when compiling Shader programs.

Target platform

SHADER_API_MOBILE is defined for all general mobile platforms (GLES, GLES3, METAL).

Additionally, SHADER_TARGET_GLSL is defined when the target shading language is GLSL (always true for OpenGL/GLES platforms).

Shader target model

SHADER_TARGET is defined to a numeric value that matches the ShaderA program that runs on the GPU. More info
See in Glossary target compilation model (that is, matching #pragma target directive). For example, SHADER_TARGET is 30 when compiling into Shader model 3.0. You can use it in Shader code to do conditional checks. For example:

#if SHADER_TARGET < 30
    // less than Shader model 3.0:
    // very limited Shader capabilities, do some approximation
#else
    // decent capabilities, do a better thing
#endif

Unity version

UNITY_VERSION contains the numeric value of the Unity version. For example, UNITY_VERSION is 501 for Unity 5.0.1. This can be used for version comparisons if you need to write Shaders that use different built-in Shader functionality. For example, a #if UNITY_VERSION >= 500 preprocessor check only passes on versions 5.0.0 or later.

Shader stage being compiled

Preprocessor macros SHADER_STAGE_VERTEX, SHADER_STAGE_FRAGMENT, SHADER_STAGE_DOMAIN, SHADER_STAGE_HULL, SHADER_STAGE_GEOMETRY, SHADER_STAGE_COMPUTE are defined when compiling each Shader stage. Typically they are useful when sharing Shader code between pixelThe smallest unit in a computer image. Pixel size depends on your screen resolution. Pixel lighting is calculated at every screen pixel. More info
See in Glossary Shaders and compute Shaders, to handle cases where some things have to be done slightly differently.

Platform difference helpers

Direct use of these platform macros is discouraged, as they don’t always contribute to the future-proofing of your code. For example, if you’re writing a Shader that checks for D3D11, you may want to ensure that, in the future, the check is extended to include Vulkan. Instead, Unity defines several helper macros (in HLSLSupport.cginc):

• UNITY_REVERSED_Z - defined on plaftorms using reverse Z buffer. Stored Z values are in the range 1..0 instead of 0..1.

Shadow mapping macros

Declaring and sampling shadow maps can be very different depending on the platform. Unity has several macros to help with this:

NOTE: Not all graphics cards support shadowmaps. Use SystemInfo.SupportsRenderTextureFormat to check for support.

Constant buffer macros

Direct3D 11 groups all Shader variables into “constant buffers”. Most of Unity’s built-in variables are already grouped, but for variables in your own Shaders it might be more optimal to put them into separate constant buffers depending on expected frequency of updates.

Use CBUFFER_START(name) and CBUFFER_END macros for that:

CBUFFER_START(MyRarelyUpdatedVariables)
    float4 _SomeGlobalValue;
CBUFFER_END

Texture/Sampler declaration macros

Usually you would use texture2D in Shader code to declare a Texture and Sampler pair. However on some platforms (such as DX11), Textures and Samplers are separate objects, and maximum possible Sampler count is quite limited. Unity has some macros to declare Textures without Samplers, and to sample a Texture using a Sampler from another Texture. Use this if you end up running into Sampler limits, and you know that several of your Textures can in fact share a Sampler (Samplers define Texture filtering and wrapping modes).

For more information, see documentation on Sampler States.

Surface Shader pass indicators

When Surface ShadersA streamlined way of writing shaders for the Built-in Render Pipeline. More info
See in Glossary are compiled, they generate a lot of code for various passes to do lighting. When compiling each pass, one of the following macros is defined:

Disable Auto-Upgrade

UNITY_SHADER_NO_UPGRADE allows you to disable Unity from automatically upgrading or modifying your shader file.

Depth Texture helper macros

Most of the time, Depth Texture are used to render Depth from the CameraA component which creates an image of a particular viewpoint in your scene. The output is either drawn to the screen or captured as a texture. More info
See in Glossary. The UnityCG.cginc include file contains some macros to deal with the above complexity in this case:

• UNITY_TRANSFER_DEPTH(o): computes eye space depth of the vertex and outputs it in o (which must be a float2). Use it in a vertex program when rendering into a depth texture. On platforms with native depth textures this macro does nothing at all, because Z buffer value is rendered implicitly.
• UNITY_OUTPUT_DEPTH(i): returns eye space depth from i (which must be a float2). Use it in a fragment program when rendering into a depth texture. On platforms with native depth textures this macro always returns zero, because Z buffer value is rendered implicitly.
• COMPUTE_EYEDEPTH(i): computes eye space depth of the vertex and outputs it in o. Use it in a vertex program when not rendering into a depth texture.
• DECODE_EYEDEPTH(i)/LinearEyeDepth(i): given high precision value from depth texture i, returns corresponding eye space depth.
• Linear01Depth(i): given high precision value from depth texture i, returns corresponding linear depth in range between 0 and 1.

Note: On DX11/12, PS4, XboxOne and Metal, the Z buffer range is 1–0 and UNITY_REVERSED_Z is defined. On other platforms, the range is 0–1.

For example, this shader would render depth of its GameObjectsThe fundamental object in Unity scenes, which can represent characters, props, scenery, cameras, waypoints, and more. A GameObject’s functionality is defined by the Components attached to it. More info
See in Glossary:

Shader "Render Depth" {
    SubShader {
        Tags { "RenderType"="Opaque" }
        Pass {
            CGPROGRAM

            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            struct v2f {
                float4 pos : SV_POSITION;
                float2 depth : TEXCOORD0;
            };

            v2f vert (appdata_base v) {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                UNITY_TRANSFER_DEPTH(o.depth);
                return o;
            }

            half4 frag(v2f i) : SV_Target {
                UNITY_OUTPUT_DEPTH(i.depth);
            }
            ENDCG
        }
    }
}