[osg-users] getting eye position / direction
Hi,
i am trying to get eyePosition and direction, more precisely, the direction of
a ray for the purpose of ray tracing.
this is what i am doing:
Code:
const osg::Vec3d collisionPoint = intersection.getWorldIntersectPoint();
...
osg::Vec3d eyeDirection = collisionPoint - _tracer->getEye();
eyeDirection.normalize();
where the _tracer->getEye() method returns the position of the eye (computed
once for a frame):
Code:
if (!_eye_set) {
osg::Vec3d center, up;
getCamera()->getViewMatrixAsLookAt(_eye, center, up);
_eye_set = true;
}
i am not sure whether this is the correct way to get the eye
position/direction. i was thinking there has to be a way to get the direction
from an intersection itself, but i am not confident using the start/end points
(transforming them into appropriate coordinates) considering i create the rays
(line segment intersectors) in WINDOW and also MODEL coordinate frames.
can anyone tell me whether my method is correct or i should rather try getting
the start/end points from the intersector, transforming them and this way
getting the ray (==eye) direction ?
Thank you!
Cheers,
Andrey[/code]
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Re: [osg-users] getting eye position / direction
HI Andrey,
I'm rather confused about what you are trying to do, you question
seems rather mixed up. Could you take a step back and explain at a
higher level what you are trying to achieve and we can then point you
in the right direction of how to achieve.
Robert.
On 9 March 2012 08:29, Andrey Ibe wrote:
> Hi,
>
> i am trying to get eyePosition and direction, more precisely, the direction
> of a ray for the purpose of ray tracing.
>
> this is what i am doing:
>
> Code:
> const osg::Vec3d collisionPoint = intersection.getWorldIntersectPoint();
> ...
> osg::Vec3d eyeDirection = collisionPoint - _tracer->getEye();
> eyeDirection.normalize();
>
>
> where the _tracer->getEye() method returns the position of the eye (computed
> once for a frame):
> Code:
>
> if (!_eye_set) {
> osg::Vec3d center, up;
> getCamera()->getViewMatrixAsLookAt(_eye, center, up);
> _eye_set = true;
> }
>
>
> i am not sure whether this is the correct way to get the eye
> position/direction. i was thinking there has to be a way to get the direction
> from an intersection itself, but i am not confident using the start/end
> points (transforming them into appropriate coordinates) considering i create
> the rays (line segment intersectors) in WINDOW and also MODEL coordinate
> frames.
>
> can anyone tell me whether my method is correct or i should rather try
> getting the start/end points from the intersector, transforming them and this
> way getting the ray (==eye) direction ?
>
> Thank you!
>
> Cheers,
> Andrey[/code]
>
> --
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=46123#46123
>
>
>
>
>
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> osg-users mailing list
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Re: [osg-users] getting eye position / direction
i am trying to compute the direction of an osg::LineSegmentIntersector object. i can get the collision point and i am trying to get the starting point - i need the vector of the intersector's direction. i do this for the purpose of ray tracing (or ray casting). i create the intersectors this way Code: new osgUtil::LineSegmentIntersector(cf, x, y); where cf is 'WINDOW' (this is for the primary rays). i am not sure how to transform the starting/end point of the intersector into model (world) space. that's why i am trying to get the position of the camera as the starting point. i looked at the code of the linesegmentintersector thoroughly, but still am confused about the matrices, so i decided it could be less difficult to use the camera. i need the vector to calculate the specular color. robert, thank you very much for your help. andrey -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=46129#46129 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] getting eye position / direction
Hi Andrey, Thanks for the explanation, make more sense now. If you have a perspective camera then you'll be able to assume that the all the line segments will start at the cameras eye point and end at the intersection point that is returned. To compute the camera's eye position in world coordinates what you need to do is multiple the (0,0,0) eye position in eye coorindates into the world coordinates by multiply it by the the inverse of the camera's view matrix. i.e. osg::Vec3d eyeInWorld = osg::Vec3d(0.0,0.0,0.0) * osg::Matrixd::inverse(camera->getViewMatrix()); Robert. On 9 March 2012 10:41, Andrey Ibe wrote: > i am trying to compute the direction of an osg::LineSegmentIntersector > object. i can get the collision point and i am trying to get the starting > point - i need the vector of the intersector's direction. > > i do this for the purpose of ray tracing (or ray casting). i create the > intersectors this way > Code: > new osgUtil::LineSegmentIntersector(cf, x, y); > > where cf is 'WINDOW' (this is for the primary rays). i am not sure how to > transform the starting/end point of the intersector into model (world) space. > that's why i am trying to get the position of the camera as the starting > point. i looked at the code of the linesegmentintersector thoroughly, but > still am confused about the matrices, so i decided it could be less difficult > to use the camera. > > i need the vector to calculate the specular color. > > robert, thank you very much for your help. > > andrey > > -- > Read this topic online here: > http://forum.openscenegraph.org/viewtopic.php?p=46129#46129 > > > > > > ___ > osg-users mailing list > osg-users@lists.openscenegraph.org > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] getting eye position / direction
again, thank you, robert. now i know i'm getting correct results. regards, Andrey -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=46391#46391 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] getting eye position / direction
Hello again! I've just realized i do need to be able to translate the starting and ending points of a LineSegmentIntersector created in WINDOW coordinate frame into the WORLD coordinate space. is there any simple method to do so ? by retrieving them from the intersector or its intersection. i couldn't find any. my guess is to take matrices, make an inverse and multiply: Code: osg::Matrix matrix; matrix.preMult( somehow.getWindowMatrix() ); matrix.preMult( somehow.getProjectionMatrix() ); matrix.preMult( somehow.getViewMatrix() ); osg::Matrix inverse; inverse.invert(matrix); startPointInWorldCoordinates = startPoint * inverse; but this seems computation-wise lengthy and i am not sure how to get all these matrices ... maybe the window matrix from viewport and the other two from camera. but I see this is done in the lineSegmentIntersector, the matrices are retrieved from the visitor, yet neither the matrices, nor the points are stored. my second guess would be inheriting the LineSegmentIntersector itself and modify the descendant to store those translated points. I found out that having a wall (or any other object) close behind the projection pane (e.g. looking into a room from a corner or from a point close to the wall) is fine in the osg::viewer, but if i take the camera as the starting point of the rays, the rays end up hitting the wall, which is not actually seen. that's why i need to start the rays not from the camera, but from the projection pane and to do so i need to be able to translate the points on it into the WORLD coordinate space. Thank you for any pointers! Cheers, Andrey -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=46698#46698 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] getting eye position / direction
update: Code: // get matrices osg::Matrix matrix; matrix.preMult(_tracer->getCamera()->getViewport()->computeWindowMatrix()); matrix.preMult(_tracer->getCamera()->getProjectionMatrix()); matrix.preMult(_tracer->getCamera()->getViewMatrix()); // invert osg::Matrix inverse; inverse.invert(matrix); // set results _startWorldPoint = getStart() * inverse; _endWorldPoint = getEnd() * inverse; ... Code: osg::Vec3d eyeDirection = collisionPoint - _tracer->getEye(); eyeDirection.normalize(); // this vector is correct, but the starting point (the eye) is not sufficient for my application osg::Vec3d newDirection = getReverseDirection(); // _reverseDirectionVector = (getEndWorldPoint() - getStartWorldPoint()).getVectorPart(); newDirection.normalize(); // this vector is slightly different, i suppose the points are not correctly positioned this approach results in similar, but not the same vectors. definitely not correct though, according to visual results. any suggestions? -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=46702#46702 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] getting eye position / direction
Hi, this post is for those reading this thread wondering how i solved the issue. I solved it by creating the line segment intersectors in model coordinate space, transforming the starting/ending point using this matrix: Code: osg::Matrixd matrix; matrix.preMult(_masterCamera->getViewport()->computeWindowMatrix()); matrix.preMult(_masterCamera->getProjectionMatrix()); matrix.preMult(_masterCamera->getViewMatrix()); _renderMatrixInverse->invert(matrix); This way the lineSegmentIntersector gets initialized correctly and the intersections are computed well. The problem itself originated elsewhere - i was using the camera as the ROOT node for intersectionVisitor, which did not behave the way expected. I encountered another issue when using the camera as the root - the invisible parts of the scene got culled away (as expected for rendering), however, while computing reflected rays, this caused serious issues, as these rays did not hit the expected objects, because they 'were not there'. I had to use own matrix transformation for the primary rays and let all the rest compute in the model coordinate space, the scene being the root (without any other transformations). take care, Andrey -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=47056#47056 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
