Question about the Matrix convention (C#/XNA)

[demonixis]

Hi,
I'm trying to add OpenVR support in my game engine which uses MonoGame as Backend.
The implementation goes well but I've problems with the matrix convention.

XNA uses the same matrix convention as directX but I haven't find any docs about the matrix convention used in OpenVR.

This is how I convert an OpenVR matrix to XNA matrix

public static Matrix ToXNA(this HmdMatrix34_t mat)
{
	var m = new Matrix(
		mat.m0, mat.m4, mat.m8, 0.0f,
		mat.m1, mat.m5, mat.m9, 0.0f,
		mat.m2, mat.m6, mat.m10, 0.0f,
		mat.m3, mat.m7, mat.m11, 1.0f);

	return m;
}

public static Matrix ToXNA(this HmdMatrix44_t mat)
{
	var m = new Matrix(
		mat.m0, mat.m4, mat.m8, mat.m12,
		mat.m1, mat.m5, mat.m9, mat.m13,
		mat.m2, mat.m6, mat.m10, mat.m14,
		mat.m3, mat.m7, mat.m11, mat.m15);

	return m;
}

It's almost OK, but the tracking data is not good (some axes are reversed). This is my WIP implementation

Thank you for your help.

[MarcVador]

OpenVR may be using Left handedness, that would explain your reversed axes.

[TheHans255]

Matrices in OpenVR are in the same format as that used by OpenGL - column major, assuming right-handed coordinate system with +x to the right, +y up, and +z toward camera. XNA matrices are row major (which you get right) but have +z away from the camera (which you need to adjust for with a FlipZ transformation of some kind).