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I am trying to get pass this error cannot convert from 'Valve.VR.HmdMatrix34_t' to 'UnityEngine.Transform' when importing MixCast SDK. Does anyone know how to cast 'Valve.VR.HmdMatrix34_t to'UnityEngine.Transform? I've looked at https://valvesoftware.github.io/steamvr_unity_plugin/api/Valve.VR.HmdMatrix34_t.html struct and it it does not help me much.

So the problem is where to find detailed information about the HmdMatrix34_t struct, to be able to cast it to Unity Transform.

P.S. The info about the struct is valuable and can be a start point for me, but I will really price a code sample where I can see how to extract unity Vector3 for position, rotation and scale (or the full Transform).

Scarpelius
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  • If the question is `where to find detailed information...` it is unfortunately off-topic here. If you can't find the information in the docs how should someone else? – derHugo Nov 11 '19 at 16:37
  • @derHugo true, but someone might have worked with the code and knows how is structured. These type of structures does not get invented over night, they inherit older structs from opengl or directx or any other framework. – Scarpelius Nov 11 '19 at 16:51

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A transformation matrix is a 4x4 array, but only 3x4 of that is really used. This is what the Valve HmdMatrix34_t ("t" for "type", it's a C thing) is. Simply inject the cell values from the HmdMatrix into the the first three rows (or columns, I always get the precedence mixed up) of a Unity Matrix4x4 and then assign it to your transform.

Where you may go wrong is understanding where the HmdMatrix sits in the scene graph, and thus whether to apply it directly or use its inverse.

Immersive
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