眾所皆知，目前NVIDIA HDR特效無法和反鋸齒功能一起開啟，包括像Far Cry、Splinter Cell: Chaos Theory都是。關於這點目前仍然有許多未知數，NVIDIA對於這個疑點的說法也很多，多到不知道哪個說法才是對的。但一個合理的推測是NVIDIA GeForce 6/7的ROP單元沒辦法對NVIDIA HDR所用的OpenEXR/FP16格式做AA反鋸齒，雖然NVIDIA曾說過是DirectX9的API限制，但硬體限制的可能性更高。因為HL2的資料片所支援的HDR效果，將可以與AA一起開啟。

Bit-tech最近跑到Valve做了有關HL2 Aftermath的訪談，原文在此:
http://www.bit-tech.net/gaming/2005..._screens/1.html

其中有一段原文:
「The coding team at Valve certainly sweated blood on getting HDR right for Source: in development since 2003, they went through no fewer than four different approaches to the HDR puzzle. Each method had pros & cons, so while one provided the overbright detail needed for blooming, its performance was "so-so" and it broke Multi-Sample Anti-Aliasing (MSAA). As cool as HDR is, Newell was adament that users would not have to sacrifice the ability to run AA in order to gain access to HDR.

By the fourth interation, the lads had cracked it: MSAA worked; it worked on all DX9 hardware, with reasonable performance on even a Radeon 9600; indeed the performance was the best of the four methods, with only a small performance hit over Half-Life 2's LDR solution.

To clarify, then: the HDR works on Shader Model 2 and Shader Model 3 hardware, and you can run it with anti-aliasing on.」

意思是Valve試了很多HDR的方案，每個都有優缺點，但負責人很堅持認為使用者不應該為了HDR而犧牲AA，因此他們的作法將可以在SM2.0或SM 3.0的硬體上同時開啟AA與HDR!而且在Radeon 9600上就可以跑了，以HL2超高程式執行效率來看，這真的很有可能!

其實Splinter Cell Chaos Thoery前陣子就有放出SM 2.0 HDR的Patch，我想HL2的做法和SCCT一樣，都是直接採用普通材質，而非OpenEXR/FP16高精度材質去做HDR運算。雖然某些HDR特效在反覆執行下，用普通材質運算會流失精度，讓畫質變差一些(SCCT的SM 2.0 HDR版就有略遜一點)，但除非定格抓圖仔細去找碴，不然一般人也不太會發現。但用普通材質去做HDR，就不會有ROP與OpenEXR格式的限制(前提是，如果這個限制真的存在的話)，因此就可以在HDR下開AA了!

老實說，我對HDR與AA不能同時開啟已經不爽很久了!

第一套用HL2 Source Engine加HDR特效的遊戲會是Day of Defeat:Source,9/26推出。之前Valve秀的Lost Coast(HDR Tech demo)還要再等一陣子，至於Aftermath....依Valve延期的習慣...不知道什麼時候會出。


HDR的天空好美啊!!