[Flightgear-devel] SGBucket::sgBucketDiff fix

[Phil Cazzola]

This is a minor bug fix for sgBucketDiff().
If you crossed the bucket size boundary, the answer for dx could be wrong.

E.g.
 going from   0:0, 21:7  to 0:7, 21:7   would give you dx = 7 (correct)
 but going from 0:0, 21:7 to 0:3, 22:0 would give you dx = 6 (instead of 7)

Previously it differenced the center longitudes of the buckets. When you
cross a boundary, the center point of the larger bucket now lies on the edge of the smaller
bucket.

  The result was a dx with an integer + 1/2 bucket, which rint() was
rounding to the nearest even int.

This function only seems to be used in TerraGear.  Source, test cases and
results attached.

Can someone with the keys review this and check it in?

Thanks,
Phil Cazzola

$ cvs diff newbucket.cxx
Index: newbucket.cxx
===================================================================
RCS file: /var/cvs/SimGear-0.3/source/simgear/bucket/newbucket.cxx,v
retrieving revision 1.3
diff -r1.3 newbucket.cxx
274,278c274,282
<     double c1_lon = b1.get_center_lon();
<     double c2_lon = b2.get_center_lon();
<     double diff_lon = c2_lon - c1_lon;
<     double span;
<     if ( sg_bucket_span(c1_lat) <= sg_bucket_span(c2_lat) ) {
---

    double diff_lon=0.0;
    double span=0.0;

    SGBucket tmp_bucket;
    // To handle crossing the bucket size boundary
    //  we need to account for different size buckets.

    if ( sg_bucket_span(c1_lat) <= sg_bucket_span(c2_lat) )
    {

283a288,299

    diff_lon = b2.get_center_lon() - b1.get_center_lon();

    if (diff_lon <0.0)
    {
       diff_lon -= b1.get_width()*0.5 + b2.get_width()*0.5 - span;
    }
    else
    {
       diff_lon += b1.get_width()*0.5 + b2.get_width()*0.5 - span;
    }

Test 1 x passed
Test 1 y passed
Test 2 x passed
Test 2 y passed
Test 3 x passed
Test 3 y passed
Test 4 x passed
Test 4 y passed
Test 5 x passed
Test 5 y passed
Test 6 x passed
Test 6 y passed
Test 7 x passed
Test 7 y passed
Test 8 x passed
Test 8 y passed
Test 9 x passed
Test 9 y passed
Test 10 x passed
Test 10 y passed
Test 11 x passed
Test 11 y passed
Test 12 x passed
Test 12 y passed
Test 13 x passed
Test 13 y passed
Test 14 x passed
Test 14 y passed
Test 15 x passed
Test 15 y passed
Test 16 x passed
Test 16 y passed
Tests completed
Total errors = 0

Test 1 x passed
Test 1 y passed
Test 2 x passed
Test 2 y passed
Test 3 x passed
Test 3 y passed
Test 4 x passed
Test 4 y passed
Test 5 x passed
Test 5 y passed
Test 6 x failed!
Expected:  7, acutal:6
Test 6 y passed
Test 7 x failed!
Expected:  7, acutal:6
Test 7 y passed
Test 8 x passed
Test 8 y passed
Test 9 x passed
Test 9 y passed
Test 10 x failed!
Expected:  7, acutal:6
Test 10 y passed
Test 11 x failed!
Expected:  7, acutal:6
Test 11 y passed
Test 12 x failed!
Expected:  7, acutal:6
Test 12 y passed
Test 13 x failed!
Expected:  164, acutal:162
Test 13 y passed
Test 14 x failed!
Expected:  -164, acutal:-162
Test 14 y passed
Test 15 x failed!
Expected:  -164, acutal:-162
Test 15 y passed
Test 16 x failed!
Expected:  -164, acutal:-162
Test 16 y passed
Tests completed
Total errors = 9

testbucket.cxx
Description: Binary data

newbucket.cxx

Description: Binary data
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