Brute Force Matcher

Overview

The brute force matcher algorithm uses query and reference descriptors provided as inputs and finds the closest (by distance) reference descriptor for every query descriptor. There is an additional option of cross checking provided, which notifies the algorithm to output only those matches that are closest to each other both ways, i.e if A is a query descriptor and B is a reference descriptor, B is closest reference descriptor to A and A is the closest query descriptor to B.

Implementation

The brute force matcher algorithm calculates the distance between query and reference descriptors provided as input. The norm for distance calculation is provided by the user. The user can also choose the number of matches they want per query descriptor, in which case the smallest N (N being the number of matches per query <= 3) distant matches are provided. The user can choose to enable or disable cross check as well.

C API functions

For list of limitations, constraints and backends that implements the algorithm, consult reference documentation of the following functions:

Function	Description
vpiSubmitBruteForceMatcher	Runs a brute force matcher algorithm on descriptors.

Usage

Language: C/C++

1. Initialization phase
   1. Include the header that defines the needed functions and structures.

      #include <vpi/algo/BruteForceMatcher.h>

   2. Define the input descriptor arrays. They have to be of type VPI_ARRAY_TYPE_BRIEF_DESCRIPTOR.

          VPIArray queryDescriptors;
          vpiArrayCreate(numDescriptors, VPI_ARRAY_TYPE_BRIEF_DESCRIPTOR, 0, &queryDescriptors);
       
          VPIArray referenceDescriptors;
          vpiArrayCreate(numDescriptors, VPI_ARRAY_TYPE_BRIEF_DESCRIPTOR, 0, &referenceDescriptors);

   3. Create the output array. It has to be of type VPI_ARRAY_TYPE_MATCHES.

          VPIArray output;
          vpiArrayCreate(numDescriptors, VPI_ARRAY_TYPE_MATCHES, 0, &output);

   4. Create the stream where the algorithm will be submitted for execution.

          VPIStream stream;
          vpiStreamCreate(0, &stream);

2. Processing phase
   1. Submit the algorithm for the brute force matcher. It'll be executed by the CPU backend.

          VPI_CHECK_STATUS(vpiSubmitBruteForceMatcher(stream, VPI_BACKEND_CPU, queryDescriptors, referenceDescriptors,
                                                      VPI_NORM_HAMMING, maxMatchesPerQuery, output, flags));

   2. Optionally, wait until the processing is done.

          vpiStreamSync(stream);

3. Cleanup phase
   1. Free resources held by the stream and the input and output arrays.

          vpiStreamDestroy(stream);
          vpiArrayDestroy(queryDescriptors);
          vpiArrayDestroy(referenceDescriptors);
          vpiArrayDestroy(output);

For more information, see Brute Force Matcher in the "API Reference" section of VPI - Vision Programming Interface.

Performance

For information on how to use the performance table below, see Algorithm Performance Tables.
Before comparing measurements, consult Comparing Algorithm Elapsed Times.
For further information on how performance was benchmarked, see Performance Benchmark.

clear filters Device: Jetson AGX Orin  -  Streams: 1 2 4 8