// File: timing.h
// Abstract: This example shows how OpenCL can be used to create a procedural field of
// grass on a generated terrain model which is then rendered with OpenGL.
// Because OpenGL buffers are shared with OpenCL, the data can remain on the
// graphics card, thus eliminating the API overhead of creating and submitting
// the vertices from the host.
// All geometry is generated on the compute device, and outputted into
// a shared OpenGL buffer. The terrain gets generated only within the
// visible arc covering the camera's view frustum to avoid the need for
// culling. A page of grass is computed on the surface of the terrain as
// bezier patches, and flow noise is applied to the angle of the blades
// to simulate wind. Multiple instances of grass are rendered at jittered
// offsets to add more grass coverage without having to compute new pages.
// Finally, a physically based sky shader (via OpenGL) is applied to
// the background to provide an environment for the grass.
// Version: <1.0>
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// Copyright ( C ) 2008 Apple Inc. All Rights Reserved.
static inline uint64_t
static inline double
SubtractTime( uint64_t uiEndTime, uint64_t uiStartTime )
static double s_dConversion = 0.0;
uint64_t uiDifference = uiEndTime - uiStartTime;
if( 0 == s_dConversion )
kern_return_t kError = mach_timebase_info( &kTimebase );
if( kError == 0 )
s_dConversion = 1e-9 * (double) kTimebase.numer / (double) kTimebase.denom;
return s_dConversion * (double) uiDifference;
© 2011 Apple Inc. All Rights Reserved. (Last updated: 2011-01-12)