eic-opticks/CSG/InstanceId.h

0001 #pragma once
0002
0003 /**
0004 InstanceId.h
0005 ===============
0006
0007 SEE CSGOptiX/InstanceId.h : 24-bit limit in early OptiX7 versions
0008 makes make bit packing inside the InstanceId not very useful
0009
0010 TODO: confirm and remove
0011
0012
0013 ::
0014
0015     epsilon:opticks blyth$ opticks-f InstanceId.h
0016     ./CSGOptiX/SBT.cc:      unsigned instance_id = optixGetInstanceId() ;        // see IAS_Builder::Build and InstanceId.h
0017     ./CSGOptiX/InstanceId.h:    unsigned instance_id = optixGetInstanceId() ;  // see IAS_Builder::Build and InstanceId.h
0018     ./CSGOptiX/CSGOptiX7.cu:    unsigned instance_id = optixGetInstanceId() ;  // user supplied instanceId, see IAS_Builder::Build and InstanceId.h
0019     ./CSGOptiX/IAS_Builder.cc://#include "InstanceId.h"
0020     ./u4/U4Step.h:    409     unsigned instance_id = optixGetInstanceId() ;  // user supplied instanceId, see IAS_Builder::Build and InstanceId.h
0021     epsilon:opticks blyth$
0022     epsilon:opticks blyth$
0023
0024
0025
0026 Beware the OptiX limits::
0027
0028     limitMaxInstanceId :   16777215    ffffff   6*4 = 24 bits
0029
0030     In [32]: 0x3fff   14bits
0031     Out[32]: 16383
0032
0033     In [19]: "%x" % ( 0x7fff | 0xffc000 )
0034     Out[19]: 'ffffff'
0035
0036     In [21]: 0x3ff
0037     Out[21]: 1023
0038
0039     In [22]: "%x"  % (0x3ff << 10)
0040     Out[22]: 'ffc00'
0041
0042         1     1
0043         3    11
0044         7   111
0045         f  1111
0046
0047 **/
0048
0049 struct InstanceId
0050 {
0051     enum { ins_bits = 14, gas_bits = 10 } ;
0052
0053     static constexpr unsigned ins_mask = ( 1 << ins_bits ) - 1 ;
0054     static constexpr unsigned gas_mask = ( 1 << gas_bits ) - 1 ;
0055
0056     static unsigned Encode(unsigned  ins_idx, unsigned  gas_idx );
0057     static void     Decode(unsigned& ins_idx, unsigned& gas_idx, const unsigned identity );
0058 };
0059
0060 inline unsigned InstanceId::Encode(unsigned  ins_idx, unsigned  gas_idx )
0061 {
0062     assert( ins_idx < ins_mask );
0063     assert( gas_idx < gas_mask );
0064     unsigned identity = (( 1 + ins_idx ) << gas_bits ) | (( 1 + gas_idx ) <<  0 )  ;
0065     return identity ;
0066 }
0067
0068 inline void InstanceId::Decode(unsigned& ins_idx, unsigned& gas_idx,  const unsigned identity  )
0069 {
0070     ins_idx = (( (ins_mask << gas_bits ) & identity ) >> gas_bits ) - 1u ;
0071     gas_idx = ((  gas_mask & identity ) >>  0 ) - 1u ;
0072 }
0073
0074
0075