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

Cosmo Player

Cosmo Player, at least the completely rewritten 2.x version, was designed with conformance and rendering accuracy as the primary goals and performance second. Currently, the latest release is version 2.1, only available for Windows 9x/NT. (An early beta is available for the PowerMac, but it is reported to be somewhat unstable; a more mature beta is available for IRIX 6.5.) With Nice Transparency turned off, Cosmo's PNG support is exemplary--aside from the fact that all partial transparency is achieved by dithering fully transparent and fully opaque pixels, an approach known as screendoor transparency or stippled alpha, which is great for performance but cannot be considered true alpha support. With Nice Transparency turned on, and regardless of whether the rendering engine is OpenGL software, OpenGL hardware, or Direct3D hardware, Cosmo 2.x displays an odd ``popping'' behavior with respect to opaque textures on translucent materials. That is, from some viewing angles, the textures will be translucent, as they are supposed to be; but from other angles, they will be completely opaque. In addition, gray textures with transparency sometimes also inherit the underlying material's transparency.

On the SGI/IRIX platform, Cosmo Player 1.0.3 is the latest official release as of March 1999.[43] Like the PC version, it has a Nice Transparency mode that incorrectly allows two-component textures (grayscale with transparency) to absorb material transparency. In addition, if two polygons with partly transparent textures intersect, it can render parts of the polygons that should be opaque as transparent instead. This latter problem can be avoided by designing the VRML world without intersecting polygons (which are often a performance problem anyway).

[43] SGI retained rights to the IRIX version of Cosmo Player and was to release at least one more version, corresponding to Cosmo Player 2.1 for Windows, early in 1999. Indeed, the first 2.1 beta for IRIX was released at the end of February.

Further information about the Windows and Macintosh versions of Cosmo Player is available from The web page for the IRIX version is at

Last Update: 2010-Nov-26