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Topics - JayAr

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Project Ideas / 6 DOF based physics games
« on: October 22, 2010, 06:23:56 AM »

right now I'm trying to build a simple sports simulation (Baseball at the moment) with 6 Degrees of freedom.
To track the orientation of the Wiimote I Use Motion Plus which is supported by GlovePie.
For tracking the position I'm trying to do stereo tracking with two other Wiimotes, so 3 Wiimotes are used in the end.

I put IR LEDs on the Wiimote which should get tracked.

As a graphics engine, I use Ogre3D. This is actually not a game engine but only graphics but you can import all kinds of libraries. So for the physics I use the Bullet library, which works pretty good (documentation is not so good, however).

Right now I only have a baseball bat and can smash objects around ;), but I want to build some other applications like billiard or badminton/tennis. Maybe something where you have to push things around would be a good demonstration if the position tracking.

The orientation works ok with MotionPlus. The tracking works somehow, but a big problem is, that the viewing angle of the Wiimote is very small, so I need to stand far away to be able to make big movements. But the the IR LEDs (Vishay 6400) arent tracked so well...
So right now I have to build a good device to put on the Wiimote with lots of LEDs  that get tracked by the two other Wiimotes.

I only tested with coin cell batteries so far? Are those two weak so will it be better with real batteries?

Also one thing I noticed. The Wii Sports Resort Swordfight Demo is kind of a reference for me. I notice that the swords orientation is tracked very well, and the recalibration of the orientation of the sword is very good there.
If you rotate with MotionPlus for a long time the orientation gets wrong after a while, so the sword recalibrates when you move slowly. I also do this recalibration. Yaw gets recalibrated by pointing to the sensor bar. Pitch and Roll can be recalibrated, because GlovePie supports a value of the Wiimote which can track Pitch and Roll if your not moving too fast. So I use this value for recalibration of Pitch and Roll.
However, I fear that the full potential of MotionPlus is not supported enough by GlovePie. In an Iwata (President of Nintendo) Asks Interview he stated, that MotionPlus would support different sensors depending on how fast you rotate the Wiimote. So in Wii Sports Resort you can move the sword really fast for a pretty long time and it still points in a good direction, so the orientation doesnt get off so fast. I really wonder if its GlovePie which doesnt support the sensor which tracks fast movement, or if Im doing something wrong.

Edit: Ping Pong:


Other / Vishay 6400 for non reflective usage
« on: August 18, 2010, 03:24:40 PM »

I want to put some IR LEDs on the Wiimote and have them tracked by two other Wiimotes. So I'm not using any reflection of the IR light, but have the LEDs directly tracked.

Now I read somewhere that the Vishay 6400 is good for Interactive Whiteboards, where the Pen points at a board, and the reflection is tracked by a Wiimote IR Camera. I was also told that the Vishay 6400 does not have a very wide viewing angle, which is actually good for the reflection at the end.

But since I dont need any reflections at all I wonder now if the Vishay 6400 is also good for my setup, or if maybe I should go for a bigger viewing angle with some other LED??


I am using Glovepie at the moment to get data from Wii MotionPlus, and it works fine.

But is there also a good support for MotionPlus with WiimoteLib now? The last update seems to be from 2009 and they say WiimoteLib can find MotionPlus but cant use the data in a useful way. I wonder if anything has changed since then, but couldnt find anything about it.


I'm using GlovePie with the Wiimote and MotionPlus.
With GlovePie it is easy to get the Rotational Speed (Pitch/Yaw/Roll) in any of the 3 Axes and therefore the Orientation of the Wiimote.

However is it also possible to get or calculate the Velocity in X/Y or Z when moving the Wiimote linear (without Rotation). With this Velocity I could calculate the translation/position of the Wiimote.
I tried to calculate the Velocity from the Acceleration (in Glovepie the Acceleration is called Wiimote.RelAccX for X Acceleration without gravity), but I couldnt really manage to get the velocity from it.
I guess this is a lot harder to do, than to get the Velocity of Rotation from the Gyrosensors, since gravity messes everything up and once there are small errors the velocity doesn't go back to zero when the Wiimote stops. Also the accelerometers for X/Y/Z also react when the Wiimote is just rotating, which also messes everything up.

So could you please tell me if its not possible at all? However in this video ( it seems that AILive have nailed it, since they are showing real 1:1 movement somehow. The sword can be stabbed forward for example. So somehow they must be able to calculate the position of the Wiimote with Orientation and Translation. I can only get Orientation at the moment.


P.S.: By the way I tried using the simple formula

v(t) = v0 + a*t

which should work for constant acceleration, but I thought it should work for changing acceleration also when it calculates 100 times per second.

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