GPGPU Programming for Games and Science

Sample Applications 411

the image domain. Thus, enforcing the boundary conditions is a postprocess-

ing task. Multiple shaders are used for this task and use ping-pong buffers.

The shaders are executed in pairs.

The boundary condition n(x) · u(x,t) = 0 may be applied on the grid

solely by setting the appropriate velocity components to zero at the boundary

cells. However, this introduces some discontinuity in the velocity near the

boundary. To counteract this, a zero-derivative condition is also applied. The

grid cells adjacent to the boundary are copied to the boundary first, then the

appropriate components are set to zero.

One shader of the pair is resp ...