High-dynamic-range rendering: Difference between revisions

Revision as of 22:39, 3 January 2022

Revision as of 16:10, 29 January 2022

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On December 24, 2002, [[Microsoft]] released a new version of [[DirectX]]. DirectX 9.0 introduced Shader Model 2.0, which offered one of the necessary components to enable rendering of high-dynamic-range images: lighting precision was not limited to just 8-bits. Although 8-bits was the minimum in applications, programmers could choose up to a maximum of 24 bits for lighting precision. However, all calculations were still integer-based. One of the first [[graphics card]]s to support DirectX 9.0 natively was [[ATI Technologies|ATI]]'s [[Radeon R300|Radeon 9700]], though the effect wasn't programmed into games for years afterwards. On August 23, 2003, Microsoft updated DirectX to DirectX 9.0b, which enabled the Pixel Shader 2.x (Extended) profile for ATI's [[Radeon R420|Radeon X series]] and NVIDIA's [[GeForce FX]] series of graphics processing units.

On August 9, 2004, Microsoft updated DirectX once more to DirectX 9.0c. This also exposed the Shader Model 3.0 profile for [[highHigh-levelLevel shaderShader languageLanguage]] (HLSL). Shader Model 3.0's lighting precision has a minimum of 32 bits as opposed to 2.0's 8-bit minimum. Also all lighting-precision calculations are now [[FLOPS|floating-point based]]. [[NVIDIA]] states that contrast ratios using Shader Model 3.0 can be as high as 65535:1 using 32-bit lighting precision. At first, HDRR was only possible on video cards capable of Shader-Model-3.0 effects, but software developers soon added compatibility for Shader Model 2.0. As a side note, when referred to as Shader Model 3.0 HDR, HDRR is really done by FP16 blending. FP16 blending is not part of Shader Model 3.0, but is supported mostly by cards also capable of Shader Model 3.0 (exceptions include the GeForce 6200 series). FP16 blending can be used as a faster way to render HDR in video games.

Shader Model 4.0 is a feature of DirectX 10, which has been released with Windows Vista. Shader Model 4.0 allows 128-bit HDR rendering, as opposed to 64-bit HDR in Shader Model 3.0 (although this is theoretically possible under Shader Model 3.0).