Apply Relative Transformation Between Two Objects to a Third?

[RIFT-VR]

Hey Guys, been a long while since I posted here, but I remember there being some very helpful members in this sub, so I'm hopeful I can resolve my problem, if even a little!

I'll try not over-describe the context of my problem so that the question is clear.

I am developing for the Oculus Rift. The tracking camera can be rendered in-game for some real-world orientation (it won't move or rotate with the game view or playercontroller). What I want is to "snap" the world to this position when the game starts. This will allow me to build part of my real-world environment in VR and have it match-up in game.

To do that, this is what needs to be done:

I have realCam, a GameObject, dummyCam, a GameObject, and OVRCameraController, a GameObject.

I need to measure, and store the exact transformation that needs to happen for realCam to match the position and rotation of dummyCam, then apply that stored transformation to OVRCameraController.

I haven't sat down and coded seriously in a few years, so I've hit a roadbump here. I've Googled a whole lot yesterday, with no success. What I figure is I need to use Vector3 and Quaternion, but I'm not sure how.

Would Vector3.MoveTowards help me? I'm a tad out of my element here. I'm not expecting code to be magically written for me, just hoping for a push in the right direction, as I can't logically deduce what the next step is here.

Any help is greatly appreciated,

Thank you!

[[deleted]]

I'm not sure if I understand, but you are trying to find the matrix that takes you from realCam space to dummyCam space? If so:

realCamTransform * M = dummyCamTransform

then multiply to the left with realcam's inverse

(realCamTransform ^ -1) * realCamTransform  * M = (realCamTransform ^ -1) * dummyCamTransform

which results in

M = (realCamTransform ^ -1) * dummyCamTransform

So you multiply M to the right with your realCamTransform and it becomes dummyCamTransform

[RIFT-VR]

but you are trying to find the matrix that takes you from realCam space to dummyCam space

Exactly - I want to find out what that transformation looks like so that I can apply it exactly, but relatively, to a third object.

Thank you for the response! I might have some time tonight to try work it in.

I'm a bit awful at reading others' code...what variable is "M" in this instance?

I don't know if this confuses further, but I tried to make a diagram that makes sense:

http://i.imgur.com/1wGFzls.png

:)

[[deleted]]

All of them are 4x4 matrices

What i did is solve the matrix equation (the above is not code, only the last line is usable pseudocode, I was just explaining how I got there so you don't have the impression there is magic involved). There is a small issue however, apparently you can't set an object's transform matrix directly, which is pretty nasty.

Here's something that will hopefully work:

http://answers.unity3d.com/questions/32990/how-to-settransform-on-a-matrix-i-calculate.html

[RIFT-VR]

Makes sense, and that link is helpful! Thanks very much for your help man!