Tag Archive for 'spacepoint fusion'

Projecting Virtual Reality with a Microvision SHOWWX

It’s bit of a stretch to call this Virtual Reality, in capitals no less, but I can’t think of another noun that fits it better.  This is the idea I have been hinting about, sprouted into a proof of concept.  By combining the stable positioning of the SpacePoint Fusion with the always in focus Microvision SHOWWX picoprojector, one can create a pretty convincing glasses-free virtual reality setup in any smallish dark room, like the bedroom in my Bay Area apartment.

Projecting Virtual Reality

This setup uses the SpacePoint to control the yaw, pitch, and roll of the camera, letting you look and aim around the virtual environment that is projected around you.  A Wii Remote and Nunchuk provide a joystick for movement and buttons for firing, jumping, and switching weapons.  All of the items are mounted to a Wii Zapper.  For now, it is annoyingly all wired to a laptop I carried around in a backpack.  Eventually, I’m planning on using a BeagleBoard and making the whole projector/computer/controller/gun setup self-contained.

The software is a hacked version of Cube, a lightweight open source first person shooter.  It’s no Crysis 2, but it runs well on Mesa on integrated graphics, and it’s a lot easier to modify for this purpose than Quake 3.  Input is via libhid for the SpacePoint and CWiid for the Wiimote.  All in all, it actually works pretty well.  The narrow field of view and immersiveness (a word, despite what my dictionary claims) makes playing an FPS quite a bit scarier for those who are easily spooked, like yours truly.  There is some serious potential in the horror/zombie/velociraptor genres for a device like this, if anyone is interested in designing a game.

This is just the start, of course.  I know I say that a lot, and there are about a dozen projects on this blog I’ve abandoned, but I think this one will hold my attention for a while.  I hate showing off anything without source code, so even though it will likely not be useful to anyone, I’ve attached the patch against the final release of Cube.


Easy Absolute Orientation: PNI SpacePoint Fusion in Python

SpacePoint Fusion

My college roommate Donnie mentioned the PNI SpacePoint Fusion in comments of the HMC5843 post, and it seemed too good to be true.  A 9 DOF controller (3 axes each of magnetometer, accelerometer, and gyro) with a Kalman filter to calculate a smooth quaternion that interfaces as a USB HID device, all for under $100.  I’d be surprised if PNI is making any profit on it.  I sound more like a shill than I’m normally comfortable with, but I’m truly impressed with this gadget. I have some plans for it involving a Microvision SHOWWX that I’m quite excited about; I’ll write more on that when it’s available in a couple of months.

SpacePoint Fusion Innards

PNI provides some Windows only sample apps that show off how weirdly stable and precise the SpacePoint Fusion is.  Luckily, since it’s a normal USB HID device (redundant, I know), and PNI provides application notes, it’s easy to use on any platform.  I wrote a Python module that uses libhid via python-hid to make it easy to prototype with in Linux.  The usage is pretty simple, as shown below.  Note that when plugging the device in, you need to keep it still for a few seconds while the gyros are calibrated.  After that, the quaternion, accelerometer, and button data can be updated 62.5 times a second.

>>> import spacepoint
>>> fusion = spacepoint.SpacePoint()
>>> print repr(fusion.quat)
(0.987518310546875, -0.04425048828125, -0.04119873046875, 0.145294189453125)
>>> print repr(fusion.accel)
(-0.054016113354999999, 0.018859863306999999, -0.89648437622400001)
>>> print repr(fusion.buttons)
(0, 0)
>>> fusion.update()
>>> print repr(fusion)
accel: (-0.054016113354999999, 0.018859863306999999, -0.89648437622400001)
 quat: (0.97186279296875, -0.233428955078125, -0.030548095703125, 0.005401611328125)
 buttons: (0, 0)

Update on February 7, 2010: I emailed PNI about a bug in the firmware, and got the following response:

Thank you for submitting the SpacePoint bug regarding libusb, Python, and Linux. You’re right! There is a bug in the SpacePoint FW that prevented opening interface 1 without opening interface 0 when using libusb under Linux. While your work around was effective in allowing the device to operate normally, one should be able to open interface 1 directly without the work around. We were able to use your Python source code to quickly diagnose and repair the bug. Please see the attached for the modified Python script. Please feel free to post this paragraph, the modified code, and all bragging rights on your blog (http://eclecti.cc/).

Units being shipped now have the fix. I modified the Python module to handle units both with and without the firmware fix and bumped the version to 0.2.

SpacePoint Python Module
Standalone spacepoint.py

Setting udev rules to get the permissions right

In most cases, the module will just work properly.  However, if you get the following error, you probably don’t have the right permissions to access the usb device.

>>> import spacepoint
>>> fusion = spacepoint.SpacePoint()
hid_force_open failed with return code 12.

On most modern Linux distros, you can fix this by setting a udev rule for the device. In Ubuntu Karmic Koala, saving the following as /etc/udev/rules.d/45-spacepoint.rules , running sudo service udev restart , and then unplugging and replugging in the device should fix it:

# PNI SpacePoint Fusion
SYSFS{idVendor}=="20ff", SYSFS{idProduct}=="0100", MODE="0664", GROUP="admin"