//

// 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>

//

// Disclaimer: IMPORTANT:  This Apple software is supplied to you by Apple Inc. ("Apple")

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//

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//

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// Copyright ( C ) 2008 Apple Inc. All Rights Reserved.

//

////////////////////////////////////////////////////////////////////////////////////////////////////

#ifndef __TIMING_H__

#define __TIMING_H__

#include <mach/mach_time.h>

#include <unistd.h>

static inline uint64_t

GetCurrentTime()

{

    return mach_absolute_time();

}

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 )

    {

        mach_timebase_info_data_t kTimebase;

        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; 

}

#endif