Re: [osg-users] Camera intrinsics
Keith Parkins wrote:
After looking at this again, I am unclear as to whether you have built
the projection matrix from the intrinsic parameters. I was assuming that
you had made it by hand. To do that you would do something like this:
//-//
// The _intrinsic variable holds the five values for the intrinsic
// matrix. The intrinsic * our pixel transform to get the projections
// matrix. The intrinsic values (itr[]) are given as five doubles
// such that:
//
//| itr[0] itr[1] itr[2] |
//| 0itr[3] itr[4] |
//| 0 0 0 |
//
//| alpha_u gamma u_0 |
//| 0alpha_v v_0 |
//| 0 0 0 |
//
//-//
void
-Camera::calcProjection() {
double alpha_u, alpha_v;
// calc alphas
alpha_u = _intrinsic[0];
double cot_theta = - _intrinsic[1]/_intrinsic[0];
double sin_theta = sqrt(1/(1+cot_theta*cot_theta));
alpha_v = _intrinsic[3] * sin_theta;
double skew = _intrinsic[1];
double u0, v0;
u0 = _intrinsic[2]; v0 = _intrinsic[4];
double left = -u0 / alpha_u * _near;
double bottom = (_screen_height-v0) / alpha_v * _near;
double right = (_screen_width - u0) / alpha_u * _near;
double top = -v0 / alpha_v * _near;
_projection[0] = 2 * _near / (right - left);
_projection[4] = 2 * _near * skew / ((right - left) * alpha_u);
_projection[5] = 2 * _near / (top - bottom);
_projection[8] = -(right + left)/(right - left);
_projection[9] = -(top + bottom)/(top - bottom);
_projection[10] = (_far + _near) / (_far - _near);
_projection[11] = 1;
_projection[14] = -2 * _far * _near/(_far-_near);
|}
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There seems to be a mismatch between the projection matrix generated by e.g.
makePerspective and the projection matrix elements you suggest here.
When I do the comparison between the two, it seems that:
_projection[5], _projection[8], _projection[9] and _projection[11] have
opposite signs.
I'm also a bit surprised that the projection matrix generated by OSG
(makePerspective) has -1 instead of 1 for _projection[11]. Maybe that has
something to do with the inversion of the Y axis (0,0 in the bottom left
instead of the top left) ?
Can you give me a suggestion why these differences exist ?
Thanks !
Benedikt.
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Re: [osg-users] Camera intrinsics
Hi Benedikt,
I don't have time to look at this right now, but off the top of my head
the sign difference that you noticed may be because I grabbed this from
a reverse projection that I did (the projection was bounced off some
mirrors to a back projection which in turn was viewed by looking into
another mirror). So if everything was flipped when you tried this, that
was probably the reason why.
-K
On Wed, 6 Apr 2011, benedikt naessens wrote:
Keith Parkins wrote:
After looking at this again, I am unclear as to whether you have built
the projection matrix from the intrinsic parameters. I was assuming that
you had made it by hand. To do that you would do something like this:
//-//
// The _intrinsic variable holds the five values for the intrinsic
// matrix. The intrinsic * our pixel transform to get the projections
// matrix. The intrinsic values (itr[]) are given as five doubles
// such that:
//
//| itr[0] itr[1] itr[2] |
//| 0itr[3] itr[4] |
//| 0 0 0 |
//
//| alpha_u gamma u_0 |
//| 0alpha_v v_0 |
//| 0 0 0 |
//
//-//
void
-Camera::calcProjection() {
double alpha_u, alpha_v;
// calc alphas
alpha_u = _intrinsic[0];
double cot_theta = - _intrinsic[1]/_intrinsic[0];
double sin_theta = sqrt(1/(1+cot_theta*cot_theta));
alpha_v = _intrinsic[3] * sin_theta;
double skew = _intrinsic[1];
double u0, v0;
u0 = _intrinsic[2]; v0 = _intrinsic[4];
double left = -u0 / alpha_u * _near;
double bottom = (_screen_height-v0) / alpha_v * _near;
double right = (_screen_width - u0) / alpha_u * _near;
double top = -v0 / alpha_v * _near;
_projection[0] = 2 * _near / (right - left);
_projection[4] = 2 * _near * skew / ((right - left) * alpha_u);
_projection[5] = 2 * _near / (top - bottom);
_projection[8] = -(right + left)/(right - left);
_projection[9] = -(top + bottom)/(top - bottom);
_projection[10] = (_far + _near) / (_far - _near);
_projection[11] = 1;
_projection[14] = -2 * _far * _near/(_far-_near);
|}
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Post generated by Mail2Forum[/quote]
There seems to be a mismatch between the projection matrix generated by e.g.
makePerspective and the projection matrix elements you suggest here.
When I do the comparison between the two, it seems that:
_projection[5], _projection[8], _projection[9] and _projection[11] have
opposite signs.
I'm also a bit surprised that the projection matrix generated by OSG
(makePerspective) has -1 instead of 1 for _projection[11]. Maybe that has
something to do with the inversion of the Y axis (0,0 in the bottom left
instead of the top left) ?
Can you give me a suggestion why these differences exist ?
Thanks !
Benedikt.
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Keith ParkinsU of R Center for Visual Science
kpark...@cvs.rochester.edu Meliora Hall, Room 253
office: (585) 275-2460 lab: (585) 275-2230
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Re: [osg-users] Camera intrinsics
Hi Ricky, This link may help you : http://old.uvr.gist.ac.kr/wlee/web/techReports/ar/Camera%20Models.html http://old.uvr.gist.ac.kr/wlee/web/techReports/ar/Camera%20Models.html Mourad ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
[osg-users] Camera intrinsics
Hi, I have a quick question. I looked up online on setting camera intrinsics (5 parameters, including radial distortion). Would I be using viewer.getCamera()-setProjectionMatrixAsPerspective(intrinsic_parameter_matrix)? Also, can I do this (with a different matrix) before rendering each frame? Thank you! Cheers, Ricky -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=30318#30318 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Camera intrinsics
Use camera-setProjectionMatrix(intrinsic_parameter_matrix); Not sure what you are trying to do with respect to the other question you have. On Tue, 27 Jul 2010, Ricky Flintoff wrote: Hi, I have a quick question. I looked up online on setting camera intrinsics (5 parameters, including radial distortion). Would I be using viewer.getCamera()-setProjectionMatrixAsPerspective(intrinsic_parameter_matrix)? Also, can I do this (with a different matrix) before rendering each frame? Thank you! Cheers, Ricky -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=30318#30318 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org Keith ParkinsU of R Center for Visual Science ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Camera intrinsics
Thank you! I am essentially changing the view (using setViewMatrix) before rendering each frame. With each new view matrix, I have a different set of intrinsic parameters and I was wondering if I can set those again. In essence, can I repeatedly change intrinsic parameters of the camera? Keith Parkins wrote: Use camera-setProjectionMatrix(intrinsic_parameter_matrix); Not sure what you are trying to do with respect to the other question you have. On Tue, 27 Jul 2010, Ricky Flintoff wrote: Hi, I have a quick question. I looked up online on setting camera intrinsics (5 parameters, including radial distortion). Would I be using viewer.getCamera()-setProjectionMatrixAsPerspective(intrinsic_parameter_matrix)? Also, can I do this (with a different matrix) before rendering each frame? Thank you! Cheers, Ricky -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=30318#30318 ___ osg-users mailing list http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org Keith ParkinsU of R Center for Visual Science ___ osg-users mailing list http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org -- Post generated by Mail2Forum -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=30320#30320 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Camera intrinsics
After looking at this again, I am unclear as to whether you have built
the projection matrix from the intrinsic parameters. I was assuming that
you had made it by hand. To do that you would do something like this:
//-//
// The _intrinsic variable holds the five values for the intrinsic
// matrix. The intrinsic * our pixel transform to get the projections
// matrix. The intrinsic values (itr[]) are given as five doubles
// such that:
//
//| itr[0] itr[1] itr[2] |
//| 0itr[3] itr[4] |
//| 0 0 0 |
//
//| alpha_u gamma u_0 |
//| 0alpha_v v_0 |
//| 0 0 0 |
//
//-//
void
-Camera::calcProjection() {
double alpha_u, alpha_v;
// calc alphas
alpha_u = _intrinsic[0];
double cot_theta = - _intrinsic[1]/_intrinsic[0];
double sin_theta = sqrt(1/(1+cot_theta*cot_theta));
alpha_v = _intrinsic[3] * sin_theta;
double skew = _intrinsic[1];
double u0, v0;
u0 = _intrinsic[2]; v0 = _intrinsic[4];
double left = -u0 / alpha_u * _near;
double bottom = (_screen_height-v0) / alpha_v * _near;
double right = (_screen_width - u0) / alpha_u * _near;
double top = -v0 / alpha_v * _near;
_projection[0] = 2 * _near / (right - left);
_projection[4] = 2 * _near * skew / ((right - left) * alpha_u);
_projection[5] = 2 * _near / (top - bottom);
_projection[8] = -(right + left)/(right - left);
_projection[9] = -(top + bottom)/(top - bottom);
_projection[10] = (_far + _near) / (_far - _near);
_projection[11] = 1;
_projection[14] = -2 * _far * _near/(_far-_near);
|}
On Tue, 27 Jul 2010, Ricky Flintoff wrote:
Hi,
I have a quick question. I looked up online on setting camera intrinsics (5
parameters, including radial distortion). Would I be using
viewer.getCamera()-setProjectionMatrixAsPerspective(intrinsic_parameter_matrix)?
Also, can I do this (with a different matrix) before rendering each frame?
Thank you!
Cheers,
Ricky
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Re: [osg-users] Camera intrinsics
Hi, Oh wow! Thank you very very much! Thank you! Cheers, Ricky -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=30328#30328 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Camera intrinsics
Hi, Sorry! I have a couple of more questions. Whats _near and _far? Also, is there any reference for these equations? Thank you again for your tremendous help. Cheers, Ricky -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=30330#30330 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
