What platforms does TerraVision support?
TerraVision runs under Windows 98/ME/NT/2000, Linux, and Silicon Graphics workstations. Currently the full system, with full user interface, runs under Unix (using X/Motif or Tcl/Tk) and Windows (using Tcl/Tk). The Netscape plugin and ActiveX component versions both work under Windows. We are considering a Mac port. • How does TerraVision represent terrain? TerraVision uses a standard multiresolution pyramid representation for all of its terrain data. This is analogous to a quad tree structure. To do this, we chop up a large terrain model (imagery or elevation) into a grid of 128 x 128 pixel tiles. We also produce versions of the image over a range of resolutions (e.g. 2048×2048, 1024×1024, 512×512, 128×128), and chop each of these up into tiles. That way, we can directly access any part of the image at any desired resolution. This allows us to interactively browse terrain datasets over the Web by only streaming the parts of the images that we actually require for the current view. • W
