[osg-users] Shapefiles Coordinate System Conversions
Hello all, I am brand new to OSG and I am still wading through all the information and examples learning as much as I can. I am working on my latest exercise in which I am overylaying a shapefile onto a terrain database that I have. The shapefile consists of bodies of water (lakes) in California. I created the terrain database using osgdem and some DTED data that I have for a small portion of California. I know that the shapefile consists of lat, lon, height data ( thanks to osgconv ) and I wanted to convert those data to x,y,z coordinates in the coordinate system of the terrain. I did this by using a node visitor for the shapefile node after reading it in with readNodeFile. I accessed the ArrayData via the Geode instance and then looped through the data using the ellipsoid model from the terrain's coordinate system to convert the lat,long,height data. Then all I had to do was the overlay stuff and add it to the root node. Anyway, what I really want to know is if there is a better solution for converting the lat,long,height data or am I on track? Any existing examples or code snippets would be much appreciated. Thanks, Greg ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Shapefiles Coordinate System Conversions
Hi Greg, It sounds like you are on track. At tip for geospatial data - With the .shp plugin in SVN head, and 2.5.x dev series the plugin supports loaded the geometry as doubles rather than the default of floats. You can enable this by using the ReaderWriter::Options object passed in with your readNodeFile call, on this options object you set the options string via options-setOptionString(double); Loading the vertex data as double helps with precision tremendously, but for rendering it totally kills performance as the graphics hard can't handle doubles, so the OpenGL driver has to convert to floats on each time you render the vertex data, so load the data, project into the appropriate coordinates system, then place with a local orign with a MatrixTransform above it to place it in its original place, and then convert the vertex data to floats. This way you can maintain a good balance between precision and performance. Robert. On Thu, Jul 24, 2008 at 3:19 PM, Greg Myers [EMAIL PROTECTED] wrote: Hello all, I am brand new to OSG and I am still wading through all the information and examples learning as much as I can. I am working on my latest exercise in which I am overylaying a shapefile onto a terrain database that I have. The shapefile consists of bodies of water (lakes) in California. I created the terrain database using osgdem and some DTED data that I have for a small portion of California. I know that the shapefile consists of lat, lon, height data ( thanks to osgconv ) and I wanted to convert those data to x,y,z coordinates in the coordinate system of the terrain. I did this by using a node visitor for the shapefile node after reading it in with readNodeFile. I accessed the ArrayData via the Geode instance and then looped through the data using the ellipsoid model from the terrain's coordinate system to convert the lat,long,height data. Then all I had to do was the overlay stuff and add it to the root node. Anyway, what I really want to know is if there is a better solution for converting the lat,long,height data or am I on track? Any existing examples or code snippets would be much appreciated. Thanks, Greg ___ 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] Shapefiles Coordinate System Conversions
Thanks for the tips Robert. I'll give them a shot. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Robert Osfield Sent: Thursday, July 24, 2008 10:03 AM To: OpenSceneGraph Users Subject: Re: [osg-users] Shapefiles Coordinate System Conversions Hi Greg, It sounds like you are on track. At tip for geospatial data - With the .shp plugin in SVN head, and 2.5.x dev series the plugin supports loaded the geometry as doubles rather than the default of floats. You can enable this by using the ReaderWriter::Options object passed in with your readNodeFile call, on this options object you set the options string via options-setOptionString(double); Loading the vertex data as double helps with precision tremendously, but for rendering it totally kills performance as the graphics hard can't handle doubles, so the OpenGL driver has to convert to floats on each time you render the vertex data, so load the data, project into the appropriate coordinates system, then place with a local orign with a MatrixTransform above it to place it in its original place, and then convert the vertex data to floats. This way you can maintain a good balance between precision and performance. Robert. On Thu, Jul 24, 2008 at 3:19 PM, Greg Myers [EMAIL PROTECTED] wrote: Hello all, I am brand new to OSG and I am still wading through all the information and examples learning as much as I can. I am working on my latest exercise in which I am overylaying a shapefile onto a terrain database that I have. The shapefile consists of bodies of water (lakes) in California. I created the terrain database using osgdem and some DTED data that I have for a small portion of California. I know that the shapefile consists of lat, lon, height data ( thanks to osgconv ) and I wanted to convert those data to x,y,z coordinates in the coordinate system of the terrain. I did this by using a node visitor for the shapefile node after reading it in with readNodeFile. I accessed the ArrayData via the Geode instance and then looped through the data using the ellipsoid model from the terrain's coordinate system to convert the lat,long,height data. Then all I had to do was the overlay stuff and add it to the root node. Anyway, what I really want to know is if there is a better solution for converting the lat,long,height data or am I on track? Any existing examples or code snippets would be much appreciated. Thanks, Greg ___ 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 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
