TroikaTronix Forum: Isadora: General: Touch Table Calibration?


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Touch Table Calibration?

DizzyLittleGirl
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Aug 6, 2008, 12:15 PM

Post #1 of 6 (1708 views)
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Touch Table Calibration?	Can't Post

Hey everyone, I'm new to the forum in the sense that I just registered, but I've been reading ever since I got Isadora about a year ago.

Anyways, I'm building a touch table using infrared lasers and an infrared camera, and a projection on a surface that the camera watches. I've started by doing a basic program in Isadora where shapes and particles follow my fingers as it moves across the table. The blob decoder and Eyes++ are picking up my fingers and translating them just fine. When my hand is right in the center of the table, the shapes follow it perfectly, but as I move my hand further from the center, the shapes travels much faster than my hand and fly off the screen.

I know there isn't a built in calibration actor for this type of thing, but does anyone have any advice so that I can keep the coordinates that the camera picks up from my hand and have them directly correspond to the shapes on the screen? I'm not sure if it's relevant, but I noticed that the values of the Blob Decoder output change when they go the Horizontal and Vertical positions.

Thanks.

skulpture
User

Aug 6, 2008, 2:14 PM

Post #2 of 6 (1700 views)
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Re: [DizzyLittleGirl] Touch Table Calibration? [In reply to]	Can't Post

If the camera sees more of the image than what is being projected then it will not be to scale - I know that this an cause scaling problems. Try moving the camera further away of closer and see what results you get.

The only other way around that is to scale it somehow. Im sure somebody on here will have an idea how to do that.

An instant without duration....

www.grahamthorne.co.uk

DizzyLittleGirl
Novice

Aug 6, 2008, 2:20 PM

Post #3 of 6 (1699 views)
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Re: [skulpture] Touch Table Calibration? [In reply to]	Can't Post

I have the projection and camera lined up perfectly, so I'm not sure if that's it, I can try to fidget around with it though.

Update: I put a 1,1 sized shape in each corner to see what the coordinates are, and they are all at 50 on the X,Y axis (1 shape at 50,50 1 shape at 50,-50 etc)

So it seems that I'm scaled at around 50%. What's the best way to get it to be 100% 1/1 ratio. Also is there a way to set perimeters on a stage so that things cannot leave the stage area?

(This post was edited by DizzyLittleGirl on Aug 6, 2008, 3:31 PM)

DizzyLittleGirl
Novice

Aug 6, 2008, 4:57 PM

Post #4 of 6 (1691 views)
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Re: [DizzyLittleGirl] Touch Table Calibration? [In reply to]	Can't Post

So I figured out that my camera is reading the coordinates in terms of all positive numbers, while Isadora reads it as a graph with negative values.

So each of my 4 corners share different values that don't translate well with the blob decoder and the shapes.
The upper left corner is 100,100 on the camera, 50,50 in Isadora
Lower left is 100,0 on the camera, 50,-50
Upper right is 0, 100 on the camera, -50,-50 in Isadora
Lower right is 0, 0 on the camera, -50, 50 in Isadora

I'm going to do some simple math to try and convert them. But I'd still like to know if Mark or anyone else has any more advice on scaling or translating values between the camera and Isadora.

skulpture
User

Aug 7, 2008, 12:24 AM

Post #5 of 6 (1637 views)
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Re: [DizzyLittleGirl] Touch Table Calibration? [In reply to]	Can't Post

Ah glad you have worked it out.

If you;re table is perfectly square then it should be fine once you have the scaling right. If the table is oblong then you may run into problems because it will be longer in length compared to width. (Just a thought)

An instant without duration....

www.grahamthorne.co.uk

DizzyLittleGirl
Novice

Aug 7, 2008, 12:13 PM

Post #6 of 6 (1560 views)
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Re: [skulpture] Touch Table Calibration? [In reply to]	Can't Post

Yeah, I threw in some calculation actors and it's working pretty well. The table is 3/4 ratio, so it is a little longer. That's something I can work out if I need to.

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