Am 03.07.2015 um 08:38 schrieb Sonya Blade:
Hi Sebastian,
> Usually you use an cosine-matrix for this. It allows to determine
the quaternion which translates one coordinate frame
>(i.e. 3 independent vectors) into another, but I think osg doesn't
have this.
Does anybody can confirm also that there is not a feature like that in
osg? These 3 vectors may seem that they are independent
but actually they are dependant, because knowing any 2 of them you can
always get the 3rd one with cross product of first two.
So any modifications on one of them affects others as well.
Uhm, yes they are independent (a cross product actually produces an
independent vector from two independent vectors ...), that what is
called an orthonormal base.
And as there is more than one '3rd' vector forming an orthonormal base
with the other two vectors, your roll is not well defined.
>I think you can use the makeRotate by applying the resulting
quaternion to the vec3(0,0,1) and (1,0,0)
> and using the makeRotate with the results somehow to get the inverse.
I already tried that without succes, the glitch here is at the bare
minimum I have to define 2 vectors (up/direction, up/right,
direction/right
etcc combinaton) but I don't how to combine those two into a quaternion ?
Simply multiply the resulting quaternions.
Or if you have the 3 orthonormal axes of your rotated model, use the
direct cosine matrix.
See:
https://en.wikipedia.org/wiki/Direction_cosine
and
https://en.wikipedia.org/wiki/Euclidean_vector#Multiple_Cartesian_bases
I'm using GMTL from http://ggt.sourceforge.net/ for the math and convert
it to osg, if this would be an option for you.
GMTL is header only, so it might be worth a try
Cheers
Sebastian
I forgot to mention that I get plenty of following errorson console
screen, when I assign direction vector, this happens when I try
to pan, move, zoom of whole scene. Could that be the source of
discrepancy ?
Seems like some dimension is calcuated to 0 or a division by zero
happens. Hard to guess without debugging it.
CullVisitor::apply(Geode&) detected NaN,
depth=nan, center=(0 -2.5 0),
matrix={
nan nan nan nan
nan nan nan nan
nan nan nan nan
35 -35 0 1
}
------------------------------------------------------------------------
Date: Thu, 2 Jul 2015 19:25:34 +0200
From: [email protected]
To: [email protected]
Subject: Re: [osg-users] Orientating model in 3D space with quaternions
Hi Sonya,
Usually you use an cosine-matrix for this. It allows to determine the
quaternion which translates one coordinate frame (i.e. 3 independent
vectors) into another, but I think osg doesn't have this.
I think you can use the makeRotate by applying the resulting
quaternion to the vec3(0,0,1) and (1,0,0) and using the makeRotate
with the results somehow to get the inverse.
Cheers
Sebastian
Dear All,
I load a model with the following code in my program, p1 and p2
are osg::Vec3 type variables and simply representing
the each ends of object in spatial space ( I also use them to find
the direction vector). What I want to achive is: to place
that model up vector always aligned facing upward ( this doesn't
mean that it must coincidence/be parallel with global
Z axis) to achieve that If I apply the quaternions then object
is positioned with correct direction vector (calulated via
p1, p2) but rolled with arbitrary angle along that direction
vector, which violates my conditional goal.
It also seems that it's not a supprise that it produces that
result bcoz nowhere I specify the crucial right or up vector with
quaternion which is required to position the object in 3D space.
So How am I supposed to correct that effect either with
quaternions or matrices ?
loadedModel = osgDB::readNodeFile("quad.obj");
osg::Vec3Array* verlist=
static_cast<osg::Vec3Array* >(rubber_line->getVertexArray());
osg::Vec3 p1 = (*verlist)[0];
osg::Vec3 p2 = (*verlist)[1];
osg::ref_ptr<osg::PositionAttitudeTransform> Transf = new
osg::PositionAttitudeTransform;
Transf->setPosition( p1 );
osg::Quat quad;
osg::Matrix matrix, mat2;
quad.makeRotate(osg::Vec3(0,1,0),p2-p1);
Transf->setAttitude(quad);
Transf->addChild(loadedModel);
rootnode->addChild(Transf);
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