[GLSL] Qualifier

 

https://thebookofshaders.com/06/

The Book of Shaders

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int newFunction(in vec4 aVec4,      // read-only
                out vec3 aVec3,     // write-only
                inout int aInt);    // read-write

 

The default is in. The inout qualifier is similar to a call by reference.