[osg-users] round earth to ECEF

[Trajce Nikolov NICK]

Hi community,

I have Round Earth database (origin set to some geo location on the
ellipsoid) and I need it into ECEF (origin at the earth center). I havn't
spend too much time thinking about possible conversion and I am asking here
for some hints, suggestions  what it would take to write some
pos-processor .. Any word from you is highly welcome

Thanks a bunch as always!

Cheers,
Nick

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trajce nikolov nick
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Re: [osg-users] 【NEWBIE】Question about osg::MatrixTransform::getMatrix().getTrans() and getRotate()

[Wojciech Lewandowski]

Hi Jiechang,

Few observations:

1. You write you want rotation around Y axis (0,1,0). But you rotate around
Z axis (0,0,1). Btw there are osg::X_AXIS = (1,0,0) , osg::Y_AXIS =
(0,1,0), osg::Z_AXIS = (0,0,1) constants defined in OSG which you may
directly.
2. What is the origin variable in your example ? This is probably the other
matrix which you premultiply and it influences your results.
3. Values stored in quaternion fields are rather non intuitive. I suggest
you just make simpler experiment. Set quaternion variable directly with
osg::Quat quat( Angle, Axis ). For example as osg::Quat quat( osg::PI_4,
osg::Z_AXIS) as you do in your example. And then examine under debugger
what constructor does and whats actually stored on 4 fields of Quat. Those
numbers won't be the same as the ones you passed to constructor. And thats
correct. You will find a plenty of info on Quaternions on the web. Look for
them if you need to learn more.
4. This line probably has wrong order of transformations -->
model1->setMatrix(origin*osg::Matrix::translate(-Center)*
osg::Matrix::rotate(osg::DegreesToRadians(45.0), 0, 0,
1)*osg::Matrix::translate(Center));
I suppose you rather want to make it like this --> model1->setMatrix(osg::
Matrix::translate(-Center)*osg::Matrix::rotate(osg::DegreesToRadians(45.0),
0, 0, 1)*osg::Matrix::translate(Center)*origin);
Reason for this is OSG uses row major matrices, so if you want to transform
vertex by matrix you do it like this: result = vert * matrix. Thus your
origin transform should be multiplied as last transform.

Hope this helps,
Wojtek Lewandowski


2017-05-05 13:54 GMT+02:00 Jiechang Guo :

> Hi,
>  I'm a newbie and not good at math.
>  Please
>  I'm so confused with osg::MatrixTransform::getMatrix().getTrans()
> and getRotate().
>  I use the code below to rotate an object around y axis about 45
> degrees.
>
> model1->setMatrix(origin*osg::Matrix::rotate(osg::DegreesToRadians(45.0),
> 0, 0, 1));
>
>   I want to get the rotation of the model, so I used the function to
> get a quat:
>
> osg::Quat rotation = model1->getMatrix().getRotate();
>
>   I thought the rotation should be like (0.7853982,0,0,1)。but the
> result is(0,0,0.382683,0,92388).
>   I've checked the source code of OSG, and I cann't get any
> inspriation from it.
>   Another case, I thought I should move the object to its center and
> do rotate then move it back (according to some book or paper). The code is
> below.
>
> osg::Vec3 Center = model1->getBound().center();
> model1->setMatrix(origin*osg::Matrix::translate(-Center)*
> osg::Matrix::rotate(osg::DegreesToRadians(45.0), 0, 0,
> 1)*osg::Matrix::translate(Center));
>
> The object is on the same position and rotation as the first case.
>I try to get the rotation, I get more confused..
>I thought I didn't change the position of the model, the tranlation
> I get
>
> osg::Vec3 translation = model1->getMatrix().getTrans();
>
> should be (0,0,0) but (-168.184,-141.218, 0) and the rotation is just like
> the first case.
>Could you please help me to figure out why I got those results?
>
> Thank you!
>
> Cheers,
> Jiechang
>
> --
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=70883#70883
>
>
>
>
>
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【NEWBIE】Question about osg::MatrixTransform::getMatrix().getTrans() and getRotate()

[Jiechang Guo]

Hi,
 I'm a newbie and not good at math. 
 Please
 I'm so confused with osg::MatrixTransform::getMatrix().getTrans() and 
getRotate().
 I use the code below to rotate an object around y axis about 45 degrees.

model1->setMatrix(origin*osg::Matrix::rotate(osg::DegreesToRadians(45.0), 0, 0, 
1));

  I want to get the rotation of the model, so I used the function to get a 
quat:

osg::Quat rotation = model1->getMatrix().getRotate();

  I thought the rotation should be like (0.7853982,0,0,1)。but the result 
is(0,0,0.382683,0,92388).
  I've checked the source code of OSG, and I cann't get any inspriation 
from it.
  Another case, I thought I should move the object to its center and do 
rotate then move it back (according to some book or paper). The code is below.

osg::Vec3 Center = model1->getBound().center();
model1->setMatrix(origin*osg::Matrix::translate(-Center)*osg::Matrix::rotate(osg::DegreesToRadians(45.0),
 0, 0, 1)*osg::Matrix::translate(Center));
   
The object is on the same position and rotation as the first case.
   I try to get the rotation, I get more confused..
   I thought I didn't change the position of the model, the tranlation I 
get 

osg::Vec3 translation = model1->getMatrix().getTrans();
   
should be (0,0,0) but (-168.184,-141.218, 0) and the rotation is just like the 
first case.
   Could you please help me to figure out why I got those results?

Thank you!

Cheers,
Jiechang

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Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=70883#70883





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