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Hi,
I am using ARToolkit Plus to detect markers from a webcam.
I am trying to understand the marker position matrix obtained using
tracker->getModelViewMatrix()[i];
I understand that this is made up of values for the transformation matrix.
As far as I can tell the x translation is when I = 12, y translation is i=
13 and z translation is i=14.
The problem I have is understanding where the origin of the co-ordinate
system is. Assuming ARToolkit follows the same convention as ARToolkit then
from this page,
http://www.hitl.washington.edu/artoolkit/documentation/tutorialcamera.htm,
then I think the origin is at the bottom left of any image. From this, and
using the axis convention shown, surely it is true that the x and z values
must always be positive, and the y value must always be negative?
However, when I have been running the toolkit I find that whilst y does stay
negative, and z is always positive, x seems to switch between positive and
negative. So the simple question I have is: where is the origin for the
co-ordinate system?
I hope I made this clear enough to understand
Thanks
Steve
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<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Hi,<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>I am using ARToolkit Plus to detect markers from a =
webcam.<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>I am trying to understand the marker position matrix
obtained using <o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>tracker->getModelViewMatrix()[i];<o:p></o:p></span>=
</font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>I understand that this is made up of values for the
transformation matrix. As far as I can tell the x translation is =
when I =3D
12, y translation is i=3D 13 and z translation is =
i=3D14.<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>The problem I have is understanding where the origin =
of the
co-ordinate system is. Assuming ARToolkit follows the same =
convention as
ARToolkit then from this page, <a
href=3D"http://www.hitl.washington.edu/artoolkit/documentation/tutorialca=
mera.htm">http://www.hitl.washington.edu/artoolkit/documentation/tutorial=
camera.htm</a>,
then I think the origin is at the bottom left of any image. From =
this,
and using the axis convention shown, surely it is true that the x and z =
values
must always be positive, and the y value must always be =
negative?<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>However, when I have been running the toolkit I find =
that whilst
y does stay negative, and z is always positive, x seems to switch =
between
positive and negative. So the simple question I have is: where is =
the
origin for the co-ordinate system?<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>I hope I made this clear enough to =
understand<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Thanks<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Steve<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
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