Hi all,

    I would like to use as the measure unit centimetres instead of
milimeters. How can I tell ARToolkit or what should I change within the
program so ARToolkit can consider that the patterns are given in centimeters
in order to get all the distances in centimeters. Is it as simple as say
i.e: patt.width=8.0 //cm, so all the calculations will be given in
centimeters??

I need to overlay a virtual room I have designed as the 3D object. The
problem is that if I use milimeters to design all the walls and furniture in
the room, the measurements are too big and I cannot render it
properly....but I would have no problem if I use centimeters (the
measurements will be 10 times smaller)...
I also thought about divide by 10 the translation components in the
transformation matrix (that is, the fourth column)....so then, the distances
camera-marker will be in centimetres and after that overlay the object (I
overlay the virtual room on the real room)....but I wonder if the rotation
componets should be changed in some factor, I mean, will the rotation
components in the transformation matrix be the same no matter if I re-scale
the translation components?? does my question make sense?  what is the best
way to do this?

any help will be apreciated...

thank you so much

Begoña.-

I'm not sure wether that matrix is handled correctly (all values used), 
but I think you would rather need to change the scale part of the 
matrix, not the translation part. The scale values are on the diagonal 
of a transformation matrix:
   sx   0   0   0
    0  sy   0   0
    0   0  sz   0
    0   0   0   1

So if you want to scale your object down by factor 10, you would just 
divide those 3 diagonal values of the matrix by 10 (they are 1 in an 
identity matrix). Don't modify the bottom right value of the matrix (4th 
row, 4th column), as this will probably mess up your calculations ;-)


Maybe this works

BSS schrieb:
> Hi all,
> 
>     I would like to use as the measure unit centimetres instead of
> milimeters. How can I tell ARToolkit or what should I change within the
> program so ARToolkit can consider that the patterns are given in centimeters
> in order to get all the distances in centimeters. Is it as simple as say
> i.e: patt.width=8.0 //cm, so all the calculations will be given in
> centimeters??
> 
> I need to overlay a virtual room I have designed as the 3D object. The
> problem is that if I use milimeters to design all the walls and furniture in
> the room, the measurements are too big and I cannot render it
> properly....but I would have no problem if I use centimeters (the
> measurements will be 10 times smaller)...
> I also thought about divide by 10 the translation components in the
> transformation matrix (that is, the fourth column)....so then, the distances
> camera-marker will be in centimetres and after that overlay the object (I
> overlay the virtual room on the real room)....but I wonder if the rotation
> componets should be changed in some factor, I mean, will the rotation
> components in the transformation matrix be the same no matter if I re-scale
> the translation components?? does my question make sense?  what is the best
> way to do this?
> 
> any help will be apreciated...
> 
> thank you so much
> 
> Begoña.-

Ok, I'm able to change that value in the second program for calibration (the
one with the grid) but in the first one I cannot change any value....I mean
the default value for distance between the dots is 40mm and the application
doesn't ask for any change......then, when running it I get the parameters I
need for the second one refered to milimeters.

Where in the code of the first on (calib_dist application ) can I change 40
to 4???

:(

-----Mensaje original-----
De: torbjorn.engedal@n ......... [mailto:torbjorn.engedal@n .........]
Enviado el: jueves, 03 de junio de 2004 8:06
Para: BSS
Asunto: Re: needing centimeters instead of milimeters


Hi Begoña,

I recall Hirokato mentioning that the unit that is being used in ARToolKit
is decided only by the unit used when calibrating the camera.

Which means if you calibrate your camera and input the lengths between the
points/lines in centimeters instead of millimeters, then you can/must use
centimeters elsewhere as well.

Best regards,
Torbjørn

-----------------------------------------------------
Torbjørn Engedal
Associated Scientist

ABB AS
Corporate Research Center
Bergerveien 12
NO-1375 Billingstad
Norway


Message from "BSS" <BegoSS@t ..........>@h .................. received on
02.06.2004 23:06
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  |      Subject:  needing centimeters instead of milimeters
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Hi all,

    I would like to use as the measure unit centimetres instead of
milimeters. How can I tell ARToolkit or what should I change within the
program so ARToolkit can consider that the patterns are given in
centimeters
in order to get all the distances in centimeters. Is it as simple as say
i.e: patt.width=8.0 //cm, so all the calculations will be given in
centimeters??

I need to overlay a virtual room I have designed as the 3D object. The
problem is that if I use milimeters to design all the walls and furniture
in
the room, the measurements are too big and I cannot render it
properly....but I would have no problem if I use centimeters (the
measurements will be 10 times smaller)...
I also thought about divide by 10 the translation components in the
transformation matrix (that is, the fourth column)....so then, the
distances
camera-marker will be in centimetres and after that overlay the object (I
overlay the virtual room on the real room)....but I wonder if the rotation
componets should be changed in some factor, I mean, will the rotation
components in the transformation matrix be the same no matter if I re-scale
the translation components?? does my question make sense?  what is the best
way to do this?

any help will be apreciated...

thank you so much

Begoña.-