Is it typical to duplicate code between shaders?

OpenGL OpenGL: Basic Coding
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I’m in the process of better understanding shaders specifically the ability to chain/combine shaders together currently I have a simple scene with cascading shadows and phong lighting (thanks to learnopengl) now if I wanted to have a plant with a wind effect or a animated character that also has shadows and lighting it seems like the solution is duplicating code is that really the answer?

My current code is this

LoadShaderProgram("CSMPhong", "Resources/Shaders/CSMPhong.vert", "Resources/Shaders/CSMPhong.frag");
LoadShaderProgram("ShadowDepth", "Resources/Shaders/ShadowDepth.vert", "Resources/Shaders/ShadowDepth.frag", "Resources/Shaders/ShadowDepth.geom");

LoadShaderProgram("CSMPhongWind", "Resources/Shaders/CSMPhongWind.vert", "Resources/Shaders/CSMPhong.frag");
LoadShaderProgram("ShadowDepthWind", "Resources/Shaders/ShadowDepthWind.vert", "Resources/Shaders/ShadowDepth.frag", "Resources/Shaders/ShadowDepth.geom");

I did realize that I could reuse other shaders so CSMPhongWind is reusing the fragment shader from CSMPhong but still this feels very error prune if I update something I’ll need to make sure every variant is also updated. So yeah is this typical or are there better alternatives?

2

It’s up to you.

Duplicating code is almost always the wrong solution. We all know the maintenance headache caused by copy/paste/modify coders. For toy simple 2 shader demos, fine. For a large code base? Not a good idea.

You can provide multiple source strings to glShaderSource().

You can use #include directives in shaders, pointing to custom code you attach to those included “files” (with ARB_shading_language_include).

You can write your own string concatenation and/or string preprocessing to “plug in” shared code.

Up to you which one works best for your scenario.

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3

Whoa that information might be game changer. Does this mean instead of creating CSMPhongWind.vert (which is a variant of CSMPhong.vert) I can just have CSMPhong.vert and then when loading shaders add on Wind.glsl which just provides the necessary data instead.

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4

Yes.

If you have shared decls or functions used between one or more shaders, that’s a perfect thing to put in these shared files. Just “call” them whereever you need them. The GLSL compiler+linker will inline them, toss out any unused code and code paths, and optimize your shader for max performance.