The PNG Guide is an eBook based on Greg Roelofs' book, originally published by O'Reilly.


WorldView is available not only as an Internet Explorer and Navigator plug-in from Intervista, but also as a slightly modified Internet Explorer component from Microsoft. The latter is known as Microsoft's MSVRML browser, and up through the June 1998 end-user release of Windows 98, it corresponded to WorldView 2.0. Subsequent versions of Win98, at least on some new PCs, and Internet Explorer 5.0 included a VRML browser corresponding to WorldView 2.1, which was Intervista's final release.[44] (Intervista never released version 2.1 as a Navigator plug-in version, however, for either Windows or PowerMac.)

[44] WorldView 2.1 was preinstalled on new machines that shipped with Intel's i740 3D accelerator.

Unlike Cosmo Software's approach, Intervista's design philosophy for WorldView appears to have emphasized performance, particularly hardware-assisted performance. This is not necessarily a bad thing--with Direct3D acceleration under Windows 95, WorldView was usually faster than Cosmo Player in my tests, sometimes much faster--but it does mean that some design decisions adversely affect PNG rendering. For example, WorldView apparently does not support texture sizes greater than 256 × 256 pixels; instead, it automatically scales down large images. It also supports screendoor transparency rather than true alpha blending (similar to Cosmo Player's behavior with Nice Transparency disabled), and it defaults to a palette-like, limited-color rendering mode, although this can be overridden by choosing Full Color graphics mode from the Options pop-up.

Beyond the intentional limitations in PNG support, WorldView suffers from some transparency bugs similar to Cosmo's. For example, grayscale PNGs with transparency also inherit the underlying material's transparency, just as in Cosmo Player 1.x for IRIX. Opaque textures, on the other hand, fail to absorb the underlying material transparency.

In addition, WorldView with hardware acceleration enabled is at the mercy of the user's graphics hardware, the quality of the video drivers supplied with the hardware, and Microsoft's DirectX (of which at least three major versions are available). Observed hardware-specific bugs include a lack of support for material transparency (3Dfx Voodoo Rush-based card) and a lack of support for material or texture transparency or for non-palette-based textures (ATI Rage Pro card). Many of these problems are likely to disappear as hardware manufacturers release more mature versions of their video drivers, but some of the limitations may simply be due to an overly aggressive use of DirectX in WorldView itself.

Note that the older WorldView 2.0 also had problems with so-called ``RGBA-palette'' PNGs, and with hardware acceleration enabled under Windows, it failed to display RGBA PNG textures at all (observed on a Rendition Vérité-based card).

WorldView is currently still available from, but as with, the site may disappear when Computer Associates completes its acquisition of Platinum.

Last Update: 2010-Nov-26