GLSL function parameters In GLSL: Common Mistakes it states:


  Functions parameters must be declared with the in, out, or inout qualifiers.


but I have never declared function parameters with in, out, or inout qualifiers and I have never run into any problems. Could this be because of my specific graphics card? What are the side effects of not using the in, out, or inout qualifiers?

Info: I am using GLSL 3.3 and I have an Intel graphics card
The GLSL Specification in section 6.1.1 &quot;Function Calling Conventions&quot; states:


The keyword in is used as a qualifier to denote a parameter is to be copied in, but not copied out.

The keyword out is used as a qualifier to denote a parameter is to be copied out, but not copied in. This should be used whenever possible to avoid unnecessarily copying parameters in.

The keyword inout is used as a qualifier to denote the parameter is to be both copied in and copied out. It means the same thing as specifying both in and out.

A function parameter declared with no such qualifier means the same thing as specifying in.