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authorNicolas Schodet2012-05-05 19:02:53 +0200
committerNicolas Schodet2012-05-05 19:02:53 +0200
commit0fcdbb1904c2f1c32c80ebe4da367742ef6e00bc (patch)
treec759272b7853cbc0ae4b0941d49ccc7e9291169f /digital/avr
parente50baf1bcea86bd969b7d87e9dd643607ef7f161 (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.c
index 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_t
diff --git a/digital/avr/modules/math/geometry/intersection.h b/digital/avr/modules/math/geometry/intersection.h
index 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.c
index 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 };