C#•2y ago

❔ Generic method that takes in a struct and calls the correctly-typed method

I'm working with OpenTK (an OpenGL binding) and I'd like to create a method that allows setting uniforms (basically variables inside of a shader). The solution I've come up with is the following. For context, Matrix4 is a struct. This method is part of my Shader class, in which I'm trying to abstract the native types.

public void SetUniform<T>(string name, T value) where T : struct
{
    if (typeof(T) == typeof(Matrix4))
    { 
        GL.UniformMatrix4(_uniforms[name], false, (Matrix4)value);
    }
}

public void SetUniform<T>(string name, T value) where T : struct
{
    if (typeof(T) == typeof(Matrix4))
    { 
        GL.UniformMatrix4(_uniforms[name], false, (Matrix4)value);
    }
}

The cast (Matrix4)value doesn't work though. I wrote it like this so that I can write a single method to set any type of uniform value, here the only implemented one is Matrix4. My question is : Is there a way to make this work, or do I have to write a method for each type of argument? If that's a bad solution, what would be a good one? (Alternatively, I could abstract uniforms further with an Uniform class so I'm not directly working with the native types in my shader abstraction, but that would also require adding an abstraction for the uniform use cases.)

11 Replies

Thinker•2y ago

If you want to use this approach then you could use if (value is Matrix4 matrix4) instead of typeof(T) == typeof(Matrix4) Otherwise, if you want different cases for different types, then personally I'd just have an overload for each type

frostfinaOP•2y ago

It still complains that cannot convert from 'ref T' to 'ref OpenTK.Mathematics.Matrix4'. I think I'll go with the overload approach though, somehow it didn't cross my mind. Thank you :)

TheRanger•2y ago

well first you need to put ref on the argument try

public void SetUniform<T>(string name, T value) where T : struct
{
    if (value is Matrix4 matrix4)
    { 
        GL.UniformMatrix4(_uniforms[name], false, ref matrix4);
    }
}

public void SetUniform<T>(string name, T value) where T : struct
{
    if (value is Matrix4 matrix4)
    { 
        GL.UniformMatrix4(_uniforms[name], false, ref matrix4);
    }
}

frostfinaOP•2y ago

That I did, that's what caused the error I sent

TheRanger•2y ago

tested it with an int and it works

frostfinaOP•2y ago

Mhh, weird Ah wait I didn't set the if like you though, that was the problem Thanks

Anton•2y ago

you should use Unsafe.As here ah nvm if the value were passed by ref, then you would use that

nukleer bomb•2y ago

This boxes the value. I would not except my value to be boxed when just calling OpenGL API

Anton•2y ago

it actually doesn't box it it shouldn't at least it's treated as a static brach by the jit

nukleer bomb•2y ago

Yeah you're right

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Generic method that takes in a struct and calls the correctly-typed method