DX10 vs DX10.1 - what am I missing?

At the SIGGRAPH graphics conference, Microsoft gave a presentation detailing some of the changes coming in DirectX 10.1. Those that are interested can view the presentation slides here. The highlights are as follows:

* DirectX 10.1 is a series of extensions to DirectX 10
* It's supported by upcoming graphics hardware, but not current DX10 hardware
* It requires (and will be part of) Vista Service Pack 1

This is business as usual, as far as DirectX is concerned. DX 10.1 hardware will be backwards compatible with DirectX 10, but current DX10 hardware won't be forward compatible. So games looking to support DX 10.1 still need a DX 10 rendering path to support today's DX10 cards. Think of it like when Microsoft released DirectX 9.0c with added Shader Model 3.0 support. Also, don't worry too much about it requiring SP1 (which isn't out yet). The DX 10.1 SDK only recently was made available, and by the time supporting hardware and DX10.1 are released to end users somewhere in the first half of 2008, SP1 should be readily available.

What are the changes? DX 10.1's goals are to offer the "complete" DX 10, giving developers better control over image quality and making mandatory some of the things that are optional in DX 10. For example, 32-bit floating point filtering is optional in DX10 (16-bit FP filtering is mandatory), but will be mandatory in DX 10.1. Also, in DX 10, the number of multisample anti-aliasing samples is optional—DX 10.1 will make 4x AA mandatory, and require two specific sample patterns. Graphics cards can offer more sample patterns, and developers can query them in their shaders. Graphics cards that are DX 10.1 compliant will have to offer programmable shader output sample masks and multisample AA depth readback. Game developers will be able to index into cube maps and perform bitwise copies from uncompressed textures to block-compressed texture formats.
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If that's a bunch of gobbledygook to you, don't sweat it. The main takeaway is this: DirectX 10.1 is a straightforward incremental update to DX 10 that forces graphics vendors to adhere to a few more set standards with regards to image quality and a couple other under-the-hood graphics features, mainly to give games more control over image quality.