Update some comment + add definition of real to half for SHADER_API_MOBILE

ScriptableRenderPipeline/Core/CoreRP/ShaderLibrary/Common.hlsl

 // Convention:
 
 // Unity is Y up - left handed
+// The lighting code assume that 1 Unity unit (1uu) == 1 meters.  This is very important regarding physically based light unit and inverse square attenuation
 
 // space at the end of the variable name
 // WS: world space
 // VertDefault
 // FragDefault / FragForward / FragDeferred
 
-// constant floating number written as 1.0  (not 1, not 1.0, not 1.0h)
+// constant floating number written as 1.0  (not 1, not 1.0f, not 1.0h)
+// Do not use "in", only "out" or "inout" as califier, no "inline" keyword either, useless.
+// When declaring "out" argument of function, they are always last
+
+// headers from ShaderLibrary do not include "common.hlsl", this should be included in the .shader using it (or Material.hlsl)
+
-// These structures need to be align on float4 to respect various packing rules from sahder language.
-// This mean that these structure need to be padded.
+// These structures need to be align on float4 to respect various packing rules from shader language. This mean that these structure need to be padded.
+// Rules: When doing an array for constant buffer variables, we always use float4 to avoid any packing issue, particularly between compute shader and pixel shaders
+// i.e don't use SetGlobalFloatArray or SetComputeFloatParams
+// The array can be alias in hlsl. Exemple:
+// uniform float4 packedArray[3];
+// static float unpackedArray[12] = (float[12])packedArray;
-// Do not use "in", only "out" or "inout" as califier, not "inline" keyword either, useless.
+// The function of the shader library are stateless, no uniform decalare in it.
+// If a function require to have both a half and a float version, then both need to be explicitly define
+#ifndef real
-// The lighting code assume that 1 Unity unit (1uu) == 1 meters.  This is very important regarding physically based light unit and inverse square attenuation
+#ifdef SHADER_API_MOBILE
+#define real half
+#define real2 half2
+#define real3 half3
+#define real4 half4
-// When declaring "out" argument of function, they are always last
+#define real2x2 half2x2
+#define real2x3 half2x3
+#define real3x2 half3x2
+#define real3x3 half3x3
+#define real3x4 half3x4
+#define real4x3 half4x3
+#define real4x4 half4x4
-// headers from ShaderLibrary do not include "common.hlsl", this should be included in the .shader using it (or Material.hlsl)
+#define REAL_MIN HALF_MIN
+#define REAL_MAX HALF_MAX
-// Rules: When doing an array for constant buffer variables, we always use float4 to avoid any packing issue, particularly between compute shader and pixel shaders
-// i.e don't use SetGlobalFloatArray or SetComputeFloatParams
-// The array can be alias in hlsl. Exemple:
-// uniform float4 packedArray[3];
-// static float unpackedArray[12] = (float[12]packedArray;
+#else
-#ifndef real
 #define real float
 #define real2 float2
 #define real3 float3
 
 #define REAL_MIN FLT_MIN
 #define REAL_MAX FLT_MAX
+
 #endif
 
 // Include language header
 
 // Computes (FastSign(s) * x) using 2x VALU.
 // See the comment about FastSign() below.
-real FastMulBySignOf(real s, real x, bool ignoreNegZero = true)
+float FastMulBySignOf(float s, float x, bool ignoreNegZero = true)
 {
 #if !defined(SHADER_API_GLES)
     if (ignoreNegZero)
 // Therefore, we treat -0 as +0 by default: FastSign(+0) = FastSign(-0) = 1.
 // If (ignoreNegZero = false), FastSign(-0, false) = -1.
 // Note that the sign() function in HLSL implements signum, which returns 0 for 0.
-real FastSign(real s, bool ignoreNegZero = true)
+float FastSign(float s, bool ignoreNegZero = true)
 {
     return FastMulBySignOf(s, 1.0, ignoreNegZero);
 }