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author committer Nicolas Schodet 2012-05-05 19:02:53 +0200 Nicolas Schodet 2012-05-05 19:02:53 +0200 0fcdbb1904c2f1c32c80ebe4da367742ef6e00bc (patch) c759272b7853cbc0ae4b0941d49ccc7e9291169f /digital/avr e50baf1bcea86bd969b7d87e9dd643607ef7f161 (diff)
digital/avr/modules/math/geometry: slightly change intersection meaning
When a segment end is exactly on the other segment, consider there is no intersection.
Diffstat (limited to 'digital/avr')
-rw-r--r--digital/avr/modules/math/geometry/intersection.c11
-rw-r--r--digital/avr/modules/math/geometry/intersection.h3
-rw-r--r--digital/avr/modules/math/geometry/test/test_geometry.c3
3 files changed, 12 insertions, 5 deletions
 diff --git a/digital/avr/modules/math/geometry/intersection.c b/digital/avr/modules/math/geometry/intersection.cindex 1f8a9278..a1daf72d 100644--- a/digital/avr/modules/math/geometry/intersection.c+++ b/digital/avr/modules/math/geometry/intersection.c@@ -25,18 +25,21 @@ #include "common.h" #include "intersection.h" -/** Compare a and b to determine if a / b is in [0:1]. Return non zero if+/** Compare a and b to determine if a / b is in ]0:1[. Return non zero if * true. */ static uint8_t intersection_div_is_in_0_1 (int32_t a, int32_t b) {+ assert (b != 0); /* Test sign, a / b < 0 if different. */- if ((a >> 31) ^ (b >> 31))+ if ((a ^ b) & 0x80000000)+ return 0;+ else if (a == 0) return 0; else if (a > 0)- return a <= b;+ return a < b; else- return a >= b;+ return a > b; } uint8_tdiff --git a/digital/avr/modules/math/geometry/intersection.h b/digital/avr/modules/math/geometry/intersection.hindex faff928c..c1998fb2 100644--- a/digital/avr/modules/math/geometry/intersection.h+++ b/digital/avr/modules/math/geometry/intersection.h@@ -31,7 +31,8 @@ * - a, b: first line segment vertices. * - c, d: second line segment vertices. *- * If AB and CD are parallel, consider there is no intersection. */+ * If AB and CD are parallel or if a vertice is exactly on the other segment,+ * consider there is no intersection. */ uint8_t intersection_segment_segment (const vect_t *a, const vect_t *b, const vect_t *c, const vect_t *d);diff --git a/digital/avr/modules/math/geometry/test/test_geometry.c b/digital/avr/modules/math/geometry/test/test_geometry.cindex 3466ad06..35511fa8 100644--- a/digital/avr/modules/math/geometry/test/test_geometry.c+++ b/digital/avr/modules/math/geometry/test/test_geometry.c@@ -245,6 +245,7 @@ test_intersection (void) vect_t v02 = { 0, 20 }; vect_t v20 = { 20, 0 }; vect_t v22 = { 20, 20 };+ vect_t v11 = { 10, 10 }; vect_t v44 = { 40, 40 }; test (intersection_segment_segment (&v00, &v22, &v20, &v02) == 1); test (intersection_segment_segment (&v00, &v22, &v02, &v20) == 1);@@ -255,6 +256,8 @@ test_intersection (void) test (intersection_segment_segment (&v22, &v44, &v02, &v20) == 0); test (intersection_segment_segment (&v00, &v44, &v02, &v20) == 1); test (intersection_segment_segment (&v44, &v00, &v02, &v20) == 1);+ test (intersection_segment_segment (&v44, &v00, &v11, &v20) == 0);+ test (intersection_segment_segment (&v44, &v00, &v20, &v11) == 0); vect_t poly[] = { { 10, 0 }, { 0, 10 }, { -10, 0 }, { 0, -10 } }; vect_t a = { 20, 10 }; vect_t b = { 10, 20 };