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DirectX8 Feature Tests

These next four tests are all demonstrating the features found in DirectX 8.x. Because there's no efficient way to emulate the pixel shader test this is dropped if the graphics card doesn't support it, however the vertex shader test and the point sprite tests can be handled by your CPU if the graphics hardware isn't up to the task. That said, the results are obviously dependent on the speed of your CPU.

Vertex Shader



The vertex shader is almost a natural evolution of the first transform and lighting (T+L) hardware introduced with nVidia’s original GeForce graphics card. While early hardware T+L allowed basic transform and lighting calculations to be handled by the graphics processing unit (GPU) and thus free up your CPU for other tasks, the use of vertex shaders now adds the ability for developers to create custom models adding greatly to their versatility. Although Vertex Shaders can be used for a variety of effects this test concentrates on skinning with one hundred vertex skinned models displayed on screen at once. As the name suggests skinning is a technique used to smooth out the joins between moving portions of an object such as the moving joints between individual bones (knees, elbows etc.).

Pixel Shader



The Pixel Shader test uses a graphics card's pixel shaders to create a cube map based bump mapped surface on the water. Pixel shaders are used because it's necessary to modify the colour of each individual pixel on a "per-pixel" basis but without making any changes to the underlying geometry of the scene. The graphics hardware must support pixel shader 1.0 and if it is to create the effect in a single pass it must support four textures per pass.

Advanced Pixel Shader



Similar to the regular pixel shader test but using the new pixel shader version 1.4 introduced in DirectX 8.1. Graphics cards that don't support pixel shader 1.4 can duplicate the effect using pixel shader 1.0 but with the penalty of requiring two passes. The water effect exhibits increased realism with the inclusion of three additional textures, a reflection texture, a refraction texture and a Fresnel texture. This allows a conventional ripple effect to be added but also for it to be combined with rippled reflections, rippled refractions which alter how objects below the surface appear and also variable reflection intensity. The latter modifies the nature of light reflected from the water surface based on the angle of viewpoint thus creating a primarily refracted or reflected effect.

Point Sprites



While a conventional object is made up of polygons, this test creates a rearing horse using some 500,000 individual particles each of which is a mere single pixel in size to stop the scene becoming fill rate limited. Particles are more often used for things like smoke and explosion effects and although hardware accelerated point sprites are very fast they are also fairly inflexible in terms of how they can be manipulated.

Primarily Tests For: The ability to accelerate point sprites in hardware and display them correctly.

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