DirectX Compute a Windows 7

8. 4. 2009

Do třetice všeho dobrého: recenze GeForce GTX 275 skrývala ještě jednu aktualitu, o níž bychom mohli vést diskuzi.

DirectX Compute Shaders

Ačkoli současné GeForce nejsou hardwarem navrženým pro DirectX 11 (více o DirectX 11 v srpnovém článku), demonstruje už Nvidia některé schopnosti Compute Shaders. Z tří prezentovaných dem vypadá Ocean daleko nejpřitažlivěji, další dvě dema spíše ukazují možnosti použití Compute Shaders pro fyziku.

Particles:

N-Body:

Popisy toho, co můžete v demech vidět ponechám v originále:

NVIDIA DirectX Compute ocean demo:
The demo shows a real-time simulated ocean under twilight lighting condition. To obtain good looking wave crests, a rather large height field has to be employed. With Microsoft's newly introduced DirectX Compute Shader we can efficiently perform FFT on GPU, thus greatly improve the performance and image quality. The water surface is mainly modeled after Jerry Tessendorf's statistic method described in the paper "Simulating Ocean Water", which is one of the most popular techniques used for water effect in today's games. Although the algorithm itself is capable of producing visually impressive result from a presumed statistic model (Phillips spectrum), previous implementations are often limited to a relatively small height field, e.g. 64x64 or 128x128, due to the slow FFT code path on CPU. For example, the demo shown here executes three 512x512 Fourier transforms on a per frame basis. On a GTX280, the transforms can be finished within 2 milliseconds.

NVIDIA DirectX Compute Shader Particles:
This sample demonstrates the use of the DirectX compute shader to simulate a large number of colliding particles. A parallel bitonic sort implemented in the compute shader is used to sort the particles into a uniform grid data structure so that the neighbors of each particle can be found quickly. The particles collide using a simple spring and damper model, but this code could be used as the basis of more sophisticated simulations such as smoothed particle hydrodynamics. The particles are rendered as spheres using the geometry and pixel shaders.

NVIDIA DirectX N-body simulation:
The n-body sample simulates the motion of bodies under gravitational attraction. It computes all n2 interactions between n bodies, which means a massive amount of computation is performed in total. It makes use of the thread group shared memory available in DirectX Compute Shader to reduce bandwidth.