How to reuse HLSL shader code?

Question

Hello!

I needed a set of shaders that curve based on the distance from camera. Basically, I took some of the default HLSL shaders Unity provides and changed the code in the vertex shader to adjust the position of the vertices.

It works great, but I would like to know if there is a way to centralize the code in the vertex shader, as it is the same in all cases, and just pass that code throughout all shaders I need, because only the fragment shader is different.

This is because if I need to change anything in the vertex shader function, I need to change it in 6 different places.

Thank you!

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Best Answer

Answer by Namey5 · Jul 04, 2017 at 10:19 AM

They're called include files. In fact, by default all surface shaders in Unity use include files and you'll find most vert/frag shaders do too. Basically, create an empty text file and call it whatever you want. Then, change the file suffix/type to '.cginc'. Then, inside this file, you don't have to add any special information, you can literally just type the lines you want to be included. For example, if you wanted to reuse just a vertex function, you could simply have the following by itself in an include file (let's call it 'Resources.cginc');

 struct appdata
 {
     float4 vertex : POSITION;
 };
 
 struct v2f 
 {
     float4 pos : SV_POSITION;
 };
 
 v2f vert (appdata v)
 {
     v2f o;
     o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
     return o;
 }

Then, in each of your shaders, at the beginning you just need to have the following;

 ...
 #pragma vertex vert
 
 #include "Resources.cginc"
 ...

And by default, the shader will use the vertex program from the include file we created, and therefore you don't even need to type it in this shader (so long as you initialise the vertex function pragma with the same name).

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Bunny83 · Jul 04, 2017 at 11:09 AM 2

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I strongly suggest to have a look at Unity's default include files which are located at:

 C:\Program Files\Unity\Editor\Data\CGIncludes\

at least on windows10. The main include file is called "UnityCG.cginc". It includes most other includes. It should give you enough examples how you can actually create "define" macros or inline methods.

In theory you could place only a code fragment into a seperate file and include it at the right spot. The #include statement literally includes the code from the specified file at the point where the statement is located.

It is common practise to wrap the include code in an include file into an #ifndef pre-processor tag to avoid that the file might be included several times in which case you would be flooded with errors.

laurG Bunny83 · Jul 04, 2017 at 12:20 PM 0

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@Bunny83 Thank you for the information! Really helps!

laurG · Jul 04, 2017 at 12:20 PM 0

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Thank you for the answer, exactly what I was looking for.

How to reuse HLSL shader code?

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