ATI Radeon 9x00 series tweak guide

OpenGL Settings

Now expand the OpenGL menu.

# of Samples. FSAA is used to alleviate a variety of image artefacts that can occur, such as texture shimmering, jagged edges or crawling jagged edges (Something which using higher resolutions cannot resolve). This option specifies the number of samples to be used when performing FSAA, options available will vary depending on Radeon installed, though with the 9700 Pro options available are App Pref, 2 Samples, 4 Samples & 6 Samples. Ticking the App Pref box allows OpenGL applications to determine which FSAA mode to use (Assuming they allow selection of FSAA in their configuration, e.g. as Soldier Of Fortune II does), otherwise FSAA will be disabled. The images beneath illustrate the effect of the various FSAA modes available in Medal of Honor: Allied Assault.

To test the performance of the available FSAA modes I ran Unreal Tournament 2003 using HardOCP’s Benchmark Utility at High Quality settings over 3 maps.

As the results show, FSAA has a minimal impact at 2X FSAA, somewhat more apparent at 4X FSAA & 6X FSAA proving to be around ½ as slow as FSAA disabled at 1280x1024 (At lower resolutions the CPU appears to limit the performance). 4X & 6X FSAA do remain highly playable at those frame rates though, more so at lower resolutions.

3DNow!. Tick this option to enable support for the AMD 3DNow! instructions set in the Radeon Drivers. This yields improved performance with supporting CPUs. If your CPU supports 3DNow!, e.g. AMD Athlon XP then Tick this, otherwise leave it Unticked, e.g. if you have a Pentium IV.

AGP Textures. Tick this setting to enable the use of AGP texturing in OpenGL applications. This is recommended so that RAM can be used as texture memory in the event Video memory is not sufficient. You should only need Untick this option should you use a PCI Radeon.

Anisotropic Filtering. Anisotropic filtering provides reduced texture aliasing & improved texture sharpness over greater distances by using a greater number of samples per pixel - with higher samples improving the effectiveness of the filtering but as a result of an increased number of samples performance will be reduced. Options available will vary depending on Radeon installed, though with the 9700 Pro options available are By Application, 2:1 Forced, 4:1 Forced, 8:1 Forced & 16:1 Forced. Selecting By Application allows OpenGL applications to determine which anisotropic filtering level to use (Assuming they allow selection of anisotropic filtering in their configuration, e.g. as Soldier Of Fortune II does), otherwise anisotropic filtering will be disabled. The images beneath illustrate the effect of some of the anisotropic filtering modes in Medal Of Honor: Allied Assault.

As you can see anisotropic filtering offers a good improvement to image quality. To test the performance of the available Anisotropic filtering modes I ran Unreal Tournament 2003 using HardOCP’s Benchmark Utility at High Quality settings over 3 maps.

The performance level with Anisotropic filtering remains good, even at 16X. Given both performance & more importantly image quality improvements I’d highly recommend setting this to at least 4X if you can afford the small enough frame rate hit, certainly it would be more worthwhile enabling Anisotropic filtering over FSAA if you can only afford to do one or the other.

Anisotropic Mode. This setting allows you to specify whether Bilinear (Performance) or Trilinear (Quality) filtering are to be used in conjunction with Anisotropic texture filtering. Trilinear texture filtering operates by taking 4 samples (texels) from 2 neighbouring Mipmaps, applies a bilinear filter to them & then interpolates the results. This results in improved image quality, with more seamless transitions between Mipmap levels & enhanced texture detail as compared to Bilinear filtering. In most instances selecting Performance will only provide a slight frame rate improvement (Particularly with newer Radeon models) & as such I’d recommend selecting Quality.

Fast ZMask Clear. Normally clearing the Z-Buffer (which needs to be done for each frame rendered) is performed by writing 0s throughout it. With this option Ticked this process is made significantly more efficient by tagging blocks of the Z-Buffer as cleared (ATI claims this uses only 1/64 the resources over Fast Z Clear disabled). You should only really consider disabling (Unticking) this feature if you wish to benchmark the performance advantage this feature offers & it shouldn’t be necessary to do so for compatibility reasons either.

Force 16bit textures. Ticking this forces the colour depth of textures to be re-sampled to 16-Bit, which will obviously have an adverse effect on the quality of higher depth textures - though will also improve performance as the affected textures will now require less bandwidth. Untick this setting for best texture quality. It is worth considering that numerous titles allow you to select the texture colour depth in-game, e.g. Soldier Of Fortune II, & as such I’d recommend leaving this Unticked. This option also doesn’t affect the colour depth an application runs at, i.e. you can still use a 32-Bit colour display depth with this ticked.

Force Z Buffer. This setting allows you to force a specific Z-Buffer depth to be used regardless of the colour depth an application is running at. Selecting App. Pref. Will allow the Z-buffer depth to be determined based on the colour depth being used by the application, i.e. 24-Bit for 32-Bit colour depth & 16-Bit for 16-Bit colour depth. Generally speaking this shouldn’t need to be adjusted, though you might wish to force a particular depth for should you find your application exhibiting strange clipping (or similar) rendering errors, in which case try toggling between Force 24bit & Force 16bit to resolve the issue. Selecting Force 16bit can also provide a slight frame rate improvement, though at the cost of Z-buffer accuracy (Which may introduce some rendering artefacts as a result). Conversely Force 24bit will ensure that the most accurate Z-buffer depth is used regardless, which provides greatest Z-buffer precision for performing depth calculations & should yield minimal rendering errors as a result.

Select ATI Radeon Tweak Guide: Troubleshooting & General Settings Rage3DTweak: Direct 3D Settings & Visual Quality compared Direct 3D Settings - continued Rage3DTweak: OpenGL Settings, Visual Q & Performance OpenGL Settings - continued Other Useful Resources & Suggestion Box

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