Migrate app from up-facing to head-mounted device

[LastBlow]

Any advice/experience on how to migrate an existing app from up-facing device to head-mounted device?

Say by multiplying the data received from the head-mounted device by a -90 degrees rotation matrix around the x axis before feeding them to the app meant for the up-facing device or... is there much more to it?

Thank you!

[AlexColgan]

Is this a Unity application, or...?

[LastBlow]

No, no Unity, stand alone app... C++, SDL, glm, GLEW, OpenGL, Bullet Physics, Leap Motion, Oculus Rift. Have full access to code and dependencies.

[LastBlow]

Everyone is having a busy Monday?

[AlexColgan]

Busy Monday

It certainly was

To port a desktop experience to VR, you'll need a few things in place. This guide is a little old, but still covers the essentials: http://blog.leapmotion.com/vr-essentials-need-build-scratch/

Another ingredient in our VR applications that you may want to tackle is timewarping, which we implemented in Unity to reduce perceived latency and reduce juddering. It's especially effective because it also resolves the discrepancies between the different framerates -- Leap tracking (~120fps), Oculus display (90 fps) and Oculus head tracking (can't recall off the top of my head). The most straightforward way to do this extrapolation would be with a Kalman filter, using the Leap Motion positional data and associated timestamps as inputs.

Let me know how it goes!

[LastBlow]

Quick update as promised...

Actually, given that I already had a functioning app, all I had to do to display the virtual hands now that the device is head-mounted was to multiply the hands MVP matrix with the 2 rotation matrices here below, -pi/2 around x and pi around y:

glm::rotate(glm::mat4(1.0f), -glm::half_pi<float>(), glm::vec3(1.0f, 0.0f, 0.0f)) *
glm::rotate(glm::mat4(1.0f), glm::pi<float>(), glm::vec3(0.0f, 1.0f, 0.0f))

Thank you for caring, Alex.