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3D Spotlight : Hardware : 3dfx Voodoo 5 5500 AGP review - Part #2


3dfx Voodoo 5 5500 AGP review
Posted by Thomas McGuire on September 13, 2000
Company: 3dfx Interactive     Product: Voodoo 5 5500 AGP

You can read the first part of 3DS' V5 5500 review here

Post filters

In Part 1 of the Voodoo 5 5500 AGP review you may have noticed me mentioning the use of post filters to achieve near 32-bit image quality, with near 16-bit performance. In the 3dfx Advanced Features tab 2 options are available for both Direct3D & OpenGL/Glide, these being Alpha Blending & 3D Filter Quality. These options control the following.

Alpha BlendingThis is used to enable dither subtraction on the destination colour during alpha blending. When dither subtraction is enabled, the dither matrix used to convert 24-bit colour to 16-bit colour is subtracted from the destination colour before applying the alpha-blending algorithm.

Setting this to Automatic will allow the program to use this dither subtraction as required. Setting it to Sharper will enable dither subtraction, resulting in a sharper image. Setting it to Smoother will disable dither subtraction, resulting in a smoother image. The Alpha blending option is ignored when running in 32-bit colour.

3D Filter Quality. Using this setting you can further improve image quality. The display image can be filtered by averaging pixel values.

Selecting High (uses two adjacent horizontal pixels from a line & the two pixels on the line below (a 2x2 box filter) to create one output pixel) will result in more pixels being averaged, resulting in a sharper image. Selecting Normal (uses four adjacent samples on a line (a 4x1 linear filter) to create one output pixel) will average less pixels than High, resulting in a smoother, blurrier image. Selecting Automatic will allow the program to use filtering as needed.

As you may have read in Reactor Critical’s Voodoo 5 review, there is an issue with screen captures & utilities like Hypersnap. Greg Kochaniak (author of Hypersnap) had the following say regarding it;

You can actually capture mostly correct colours from Voodoo5 with HyperSnap-DX 3.63. I say "mostly", because I can do only a "frame buffer" shot from that card. The colour filter & post-processing, that I have for Voodoo - Voodoo3 cards, was not updated so far by 3dfx to provide even better shots from Voodoo5. I'm trying to talk them into fixing this code, but don't know what will happen.

That said, only OpenGL/Glide is affected by this. Direct3D remains unaffected by this screen capture issue at all. Here’s some screenshots to illustrate the effects of the Post filter (NOTE – These screenshots were taken using a special environmental variable, thanks Rev., & as such they are correct in there visual accuracy – Reactor Critical’s shots aren’t entirely accurate as you can read here, See Kenguru’s post where he states “You are right, I did not knew about Glide special shot key.). For the purposes of these shots Texture compression & FSAA were disabled.

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