Help with perspective projection

[DevTaube]

I need help with creating the projection-view matrix for a perspective camera.
I have this piece of code already...

viewMatrix.setLookAt(position, cameraLookAt, cameraUp);
projectionMatrix.setPerspective(fov, aspectRatio, nearPlane, farPlane);
Matrix4f projectionViewMatrix = new Matrix4f().set(projectionMatrix).mul(viewMatrix);
// projectionViewMatrix holds the result

...that generates a `Matrix4f` that I can pass to my vertexshader to convert world coordinates to NDC.
This currently works... kinda. Everything that gets rendered is inverted on the Y-axis (upside down).
I've looked for solutions online, tried the various invert-methods of the `Matrix4f`-class,
but everything I tried just does not render anything.

[DevTaube]

Oh wow. The issue actually does not have anything to do with JOML. I rendered my frame buffers upside down...
JOML works perfectly fine, and no further method calls were needed.
To the author(s) of JOML: Thank you for making JOML (I would have to write A LOT of code otherwise...)!