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Change new mirrorAngle to mirrorAngleOrigin, improved javadocs.

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The old mirrorAngle mirrors around the "y-axis" (PI/2 or -PI/2 as appropriate)
which is necessary for other code (particularly angularDifference) to work
correctly. The new mirrorAngleOrigin mirrors around the "x-axis" (zero).
This commit is contained in:
Michael Bayne
2013-02-12 14:24:04 -08:00
parent 0ffabf1419
commit f26a72c26f
2 changed files with 34 additions and 4 deletions
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src/main/java/pythagoras/f/MathUtil.java
+12 -1
View File
@@ -166,9 +166,20 @@ public class MathUtil
} }
/** /**
* Returns the mirror angle of the specified angle (assumed to be in [-pi, +pi]). * Returns the mirror angle of the specified angle (assumed to be in [-pi, +pi]). The angle is
* mirrored around the PI/2 if it is positive, and -PI/2 if it is negative. One can visualize
* this as mirroring around the "y-axis".
*/ */
public static float mirrorAngle (float a) { public static float mirrorAngle (float a) {
return (a > 0f ? FloatMath.PI : -FloatMath.PI) - a;
}
/**
* Returns the mirror angle of the specified angle (assumed to be in [-pi, +pi]). The angle is
* mirrored around the origin (zero degrees). One can visualize this as mirroring around the
* "x-axis".
*/
public static float mirrorAngleOrigin (float a) {
return a + (a > 0f ? -FloatMath.PI : FloatMath.PI); return a + (a > 0f ? -FloatMath.PI : FloatMath.PI);
} }
src/test/java/pythagoras/f/MathUtilTest.java
+22 -3
View File
@@ -12,8 +12,27 @@ import static org.junit.Assert.*;
*/ */
public class MathUtilTest public class MathUtilTest
{ {
@Test public void testMirrorAngle() { public static final float PI = FloatMath.PI;
assertEquals(-MathUtil.HALF_PI, MathUtil.mirrorAngle(MathUtil.HALF_PI), MathUtil.EPSILON); public static final float PI2 = FloatMath.PI/2;
assertEquals(MathUtil.HALF_PI, MathUtil.mirrorAngle(-MathUtil.HALF_PI), MathUtil.EPSILON); public static final float PI4 = FloatMath.PI/4;
public static final float PI8 = FloatMath.PI/8;
@Test public void testLerpa() {
assertEquals(MathUtil.lerpa(PI4, -PI4, 0.25f), PI8, MathUtil.EPSILON);
assertEquals(MathUtil.lerpa(PI4, -PI4, 0.75f), -PI8, MathUtil.EPSILON);
assertEquals(MathUtil.lerpa(-PI4, PI4, 0.25f), -PI8, MathUtil.EPSILON);
assertEquals(MathUtil.lerpa(-PI4, PI4, 0.75f), PI8, MathUtil.EPSILON);
// make sure we lerp the shortest route around the circle
assertEquals(MathUtil.lerpa(3*PI4, PI4, 0.5f), PI2, MathUtil.EPSILON);
assertEquals(MathUtil.lerpa(PI4, 3*PI4, 0.5f), PI2, MathUtil.EPSILON);
assertEquals(MathUtil.lerpa(-3*PI4, -PI4, 0.5f), -PI2, MathUtil.EPSILON);
assertEquals(MathUtil.lerpa(-PI4, -3*PI4, 0.5f), -PI2, MathUtil.EPSILON);
assertEquals(MathUtil.lerpa(3*PI4, -3*PI4, 0.5f), -PI, MathUtil.EPSILON);
}
@Test public void testMirrorAngleOrigin() {
assertEquals(-PI2, MathUtil.mirrorAngleOrigin(PI2), MathUtil.EPSILON);
assertEquals(PI2, MathUtil.mirrorAngleOrigin(-PI2), MathUtil.EPSILON);
} }
} }