Thanks for the ideas Hamish. I'm pretty sure that there is a conversion from geographic coordinates in xyz to arbitrary screen coordinates in the OGL code section. I understand what Helena is hoping for, and this would indeed be the ideal. To me, this 'natural' ratio between xy and z should have a z-exag value of 1.0. I have tried to estimate this in the wxPython code, but it is a rough hack and the calculation really should take place in the conversion code for OGL, not in instantiating the slider code where I put it.
Michael ____________________ C. Michael Barton Director, Center for Social Dynamics & Complexity Professor of Anthropology, School of Human Evolution & Social Change Arizona State University voice: 480-965-6262 (SHESC), 480-727-9746 (CSDC) fax: 480-965-7671 (SHESC), 480-727-0709 (CSDC) www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu On Nov 25, 2011, at 11:36 PM, Hamish wrote: > Helena wrote: >> - in wxnviz to avoid the very small zexag for latlong, > > another idea for lat/lon z-exag: just figure out what is 20-25% of the canvas > height (or ~15% of the north-south image width), > and work backwards from there, rounding to the nearest nice > round number. > > I don't know if there is any real way to escape from x:y:z ratios > of 1 : 1 : 1/(1852*60), as anything other than that is numerically > synthetic. if taking up the 1:cos(lat) aspect ratio adjustment > perhaps rather than converting the elevation data to degrees, > we could convert the ew, ns to "meters" to get ratios of > 1852*60*cos(lat): 1852*60 : 1 as the cheap and dirty projection. > for global lat/lon views you probably wouldn't want to do that > though. > > > Hamish _______________________________________________ grass-dev mailing list grass-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-dev