Hi, The way the resolution works is thus (once again, this is just from memory, so no guarantees an accuracy):
Level 0 will cover the entire bounds in a single texture (assuming you use the defaults, this will be 256x256 pixels). Level 1 will then split the terrain into two or more textures. The number of textures that are created depends on the aspect ratio of the source data. I think you will always end up with either one row or one column, with the required number of rows/columns to maintain the aspect ratio. For example, for a whole world database (twice as many lon values as lat), you will end up with one row, two columns (each tile is 180 degrees width and height). >From this point, things get easier, as for each level, each texture is divided >into four textures which cover the same region, a standard quad tree. To >calculate the resolution of a level you simply divide the number of pixels by >the covered area. As a simple example, lets say your source data covers a quarter of the world from 0-90 lat and 0-90 lon. At level 0, this is covered by 256x256 pixels, therefore the resolution is 90/256 degrees per pixel. At level 1, this is covered by 512x512 pixels, therefore the resolution is 90/512 degrees per pixel. At level 2, this is covered by 1024x1024 pixels, therefore the resolution is 90/1024 degrees per pixel. etc etc To calculate the resolution of your source imagery use something like gdalinfo to get the required details. I am sure everything is now as clear as mud for you : ) Cheers, Brad -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Chris Ess Sent: Tuesday, 13 September 2011 5:49 AM To: [email protected] Subject: Re: [osg-users] [vpb] Multiple maps in model with osgdem? (vpb) Thanks Brad, that worked. My (hopefully) final issue is trying to set the levels correctly to update the texture at an appropriate time. I have been tinkering with it attempting to get it using trial and error. However, it takes a long time to build the map so each of my adjustments is causing me to wait close to 45 mins each before I see how it has changed. Is there any rule of thumb or equation that can help give me better results? Cheers, Chris ------------------ Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=42659#42659 _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ------------------------------------------------------------------------- DISCLAIMER: This e-mail transmission and any documents, files and previous e-mail messages attached to it are private and confidential. They may contain proprietary or copyright material or information that is subject to legal professional privilege. They are for the use of the intended recipient only. Any unauthorised viewing, use, disclosure, copying, alteration, storage or distribution of, or reliance on, this message is strictly prohibited. No part may be reproduced, adapted or transmitted without the written permission of the owner. If you have received this transmission in error, or are not an authorised recipient, please immediately notify the sender by return email, delete this message and all copies from your e-mail system, and destroy any printed copies. Receipt by anyone other than the intended recipient should not be deemed a waiver of any privilege or protection. Thales Australia does not warrant or represent that this e-mail or any documents, files and previous e-mail messages attached are error or virus free. ------------------------------------------------------------------------- _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
