Hi,
I'm working on a tool that visualizes a spacecraft in orbit around a planetary
body. As it is set up now, the position of that spacecraft is given relative to
the center of the body as an x,y,z coordinate. What I'm trying to do right now
is set up a simple altimeter that looks essentially like a ruler reaching from
the planetary surface up to a little past the spacecraft. That is, a straight
line with perpendicular lines crossing it at regular intervals.
The black circle is the spacecraft, the black blob at the bottom is the
planetary surface, and I'm trying to draw that "ladder" with regular
demarkations.
I'm VERY new at OSG (two weeks in) so I could be going about this completely
wrong, please let me know if so. What needs to happen is for the altimeter to
follow the spacecraft (position given by "end" in the code) such that the
central line always intersects it and the origin stays at the center of the
planet (given by "start").
I've included the code here for building the altimeter. It outputs a group that
is attached to the root node to which the planet is also attached.
Code:
osg::Group* Visualizer::getAltimeter(osg::Vec3 start, osg::Vec3 end, int
interval)
{
int distance = sqrt(pow(end[0]-start[0],2) + pow(end[1]-start[1],2) +
pow(end[2]-start[2],2));
osg::Group* g = new osg::Group();
osg::Geode* geode = new osg::Geode();
//Line running up the middle
osg::Geometry* line_x_red = new osg::Geometry();
osg::Vec3Array* verticesx = new osg::Vec3Array(2);
(*verticesx)[0]=start;
(*verticesx)[1]=end;
line_x_red->setVertexArray(verticesx);
// set the color
osg::Vec4Array* red = new osg::Vec4Array;
red->push_back(osg::Vec4(1.0f,0.0f,0.0f,1.0f));
line_x_red->setColorArray(red);
line_x_red->setColorBinding(osg::Geometry::BIND_OVERALL);
// set the normal in the same way color.
osg::Vec3Array* normals = new osg::Vec3Array;
normals->push_back(osg::Vec3(0.0f,0.0f,-1.0f));
line_x_red->setNormalArray(normals);
line_x_red->setNormalBinding(osg::Geometry::BIND_OVERALL);
line_x_red->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::LINES,0,2));
//Surface of planet, no need to mark below this
int surfaceE = 100000;
int numMarkers = (distance-surfaceE)/interval;
osg::Geometry* marker[numMarkers];
//Construct elevation marks
for(int i = 0; i<numMarkers;i++)
{
marker[i] = new osg::Geometry();
osg::Vec3Array* vertices = new osg::Vec3Array(2);
(*vertices)[0]=osg::Vec3(-50,i*interval + surfaceE,0);
(*vertices)[1]=osg::Vec3(50,i*interval + surfaceE,0);
marker[i]->setVertexArray(vertices);
marker[i]->setColorArray(red);
marker[i]->setColorBinding(osg::Geometry::BIND_OVERALL);
marker[i]->setNormalArray(normals);
marker[i]->setNormalBinding(osg::Geometry::BIND_OVERALL);
marker[i]->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::LINES,0,2));
geode->addDrawable(marker[i]);
}
geode->addDrawable(line_x_red);
altimeterFrame = new osg::PositionAttitudeTransform();
altimeterFrame->addChild(geode);
g->addChild(altimeterFrame);
return g;
}
If this is a good way to go about it, my next question is about normals, which
I don't fully understand. I'd like the lines to appear bright red, regardless
of which angle they're viewed from. An added bonus would be for the markers to
rotate around the central line to always face the camera. I imagine this could
be done with Billboards, but some initial experimentation showed I have a lot
to learn regarding them.
This is my first post on this board, so excuse me if I've missed a point of
etiquette, I'd be glad to elaborate on anything if need be. All advice is
greatly appreciated.
Thank you!
Cheers,
Rusty
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=38368#38368
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