3dfx used to be a brand name for the folks behind Voodoo graphics, the pioneers behind Glide which fell by the wayside as DirectX and Direct3D (mostly through business bullying by MS) became standard, till some aggravated coders created OpenGL, which literally stands for Open Glide. When a programming language is called Open, that should help you understand the nature of why it has had some success despite Direct3D's near-stranglehold on the industry.What is the 3dfx patch? It comes with nGlide, which is supposed to emulate 3dfx. If it is another patch, I'm willing to try if it will help.
It's the same graphic technology as we used to see but retooled for use on more modern systems. Glide has fell by the wayside for support since OpenGL has surpassed some of its limitations. However, that doesn't stop coders from using a wrapper tailored for an individual game.
The patch implemented by PopsiclePete and co is in OpenGL whereas GOG uses a Glide wrapper. Two avenues of some of the same graphics we experienced during Voodoo days. It all comes down to programming language, but that's out of my expertise.