On 12/07/2012 12:27 PM, Paul Martz wrote:
(Sorry if this shows up twice; I originally posted it Tuesday but it
has not echoed back to the list. Test emails seem to work, so trying
again...)
Hi Jeremy -- Since you know the FOV in y (it's 45.0 degrees), you can
compute the distance to "fit" a bounding sphere with the following code:
double computeInitialDistanceFromFOVY( const osg::BoundingSphere& bs,
const double fovy )
{
return( bs.radius() / sin( osg::DegreesToRadians( fovy * .5 ) ) );
}
That code comes from the matrix utility library (osgwMx) in the
osgWorks project, but equivalent code exists in osgGA to compute home
positions, which you could also use as a reference.
-Paul
Cool, thanks!
Chris Hanson explained this to me off the lists, as well. It's actually
REALLY simple trig, but for whatever reason I just haven't ever thought
of 3D math as anything other than voodoo magic.
Now, of course, it makes perfect sense, and I honestly think I've
acquired a whole new perspective at solving problems in graphics
mathmatically. I even went and picked myself up a trig/calc book at B&N
to worth through over the next few weeks.
On 12/4/2012 7:47 AM, Jeremy Moles wrote:
Hello everyone! I'm writing a bit of code using parts of OSG and pure
OpenGLES2.
This isn't exactly an OSG question, per se, but there are a lot of
OpenGL
experts here and this is a great resource. :) Any help is appreciated!
In my particular scene, I do not maintain a matrix representing my
"camera";
there is a global projection matrix and each Drawable maintains its
own model
matrix. For this reason, whether pedantically right or wrong, I say
that my
camera always sits at 0, 0, 0 and looks into a frustum created using the
equivalent of gluPerspective(45, 1, 1, 100).
What I'm looking for is the trigonometric calculation that would
allow me to
determine either the Z value to translate my scene or the scale to
apply to my
scene in order to fit the entire thing cleanly into my viewport.
I have both the osg::BoundingBox and osg::BoundingSphere of my scene,
but since
I'm not using a camera manipulator or view matrix directly, I can't
simply
reference the code in CameraManipulator.cpp.
Furthermore: I have this working currentls in a VERY TERRIBLE way. :)
What I do
is use reimplementations of gluProject and gluUnproject to caclulate
screen-to-world and world-to-screen coordinates. I then use those
values to
figure out how much to scale my scene by, but this feels so wrong
(and bound to
a known window size) that I know there must be a better way.
Thanks!
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