comp.lang.idl-pvwave archive - RDF feed
type: channel
description: Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
items: Re: shaded relief

Re: shaded relief
type: item
description: Have you tried fiddling around with {x,y,z}range keywords in shade_surf to get the right aspect ratios for the axis? Ciao, Paolo greg michael wrote: > I want a method to generate fast shaded relief views from a surface > elevation grid (pixel for pixel orthogonal views which overlay) > > I tried using direct graphics with something like: > > shade_surf,dtm,image=sh,az=0,ax=90,position=[0,0,768,768],ti ck=0,xstyle=1,ystyle=1 > > This works, except that the z-scale is auto-scaled producing an > unrealistic exaggeration. shade_surf doesn't take an /isotropic > keyword. > [...]
creator: Paolo Grigis
date: 2007-01-19T10:29:23-00:00

Re: shaded relief
type: item
description: Thanks Paulo - that's a good suggestion. It works. Unfortunately it brings a new problem: now the image is very low contrast (because of the reduced range of slopes), having a brightness range of only about 10/256. After stretching it doesn't look very good. Now I think of it, I'm surprised the object-graphics one doesn't look the same. There must be some auto-stretching going on there. Maybe this is a killer for the direct-graphics way? Greg IDL> z=dtm*128./58000.+50. IDL> shade_surf,z,image=sh,az=0,ax=90,position=[0,0,762,768],tick =0,xstyle=1,ystyle=1,xrange=[0,768],yrange=[0,768],zrange=[0 ,768] Paolo Grigis wrote: > Have you tried fiddling around with {x,y,z}range keywords in > shade_surf to get the right aspect ratios for the axis? > > Ciao, > Paolo > > greg michael wrote: >> I want a method to generate fast shaded relief views from a surface >> elevation grid (pixel for pixel orthogonal views which overlay) >> >> I tried using direct graphics with something like: >> >> shade_surf,dtm,image=sh,az=0,ax=90,position=[0,0,768,768],ti ck=0,xstyle=1,ystyle=1 >> >> This works, except that the z-scale is auto-scaled producing an >> unrealistic exaggeration. shade_surf doesn't take an /isotropic >> keyword. >> [...]
creator: greg michael
date: 2007-01-19T11:48:11-00:00