org.locationtech.jts:jts-core 1.18.0

## Class TrianglePredicate

• ```public class TrianglePredicate
extends Object```
Algorithms for computing values and predicates associated with triangles. For some algorithms extended-precision implementations are provided, which are more robust (i.e. they produce correct answers in more cases). Also, some more robust formulations of some algorithms are provided, which utilize normalization to the origin.
Author:
Martin Davis
• ### Constructor Summary

Constructors
Constructor and Description
`TrianglePredicate()`
• ### Method Summary

All Methods
Modifier and Type Method and Description
`static boolean` ```isInCircleCC(Coordinate a, Coordinate b, Coordinate c, Coordinate p)```
Computes the inCircle test using distance from the circumcentre.
`static boolean` ```isInCircleDDFast(Coordinate a, Coordinate b, Coordinate c, Coordinate p)```
`static boolean` ```isInCircleDDNormalized(Coordinate a, Coordinate b, Coordinate c, Coordinate p)```
`static boolean` ```isInCircleDDSlow(Coordinate a, Coordinate b, Coordinate c, Coordinate p)```
Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise).
`static boolean` ```isInCircleNonRobust(Coordinate a, Coordinate b, Coordinate c, Coordinate p)```
Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise).
`static boolean` ```isInCircleNormalized(Coordinate a, Coordinate b, Coordinate c, Coordinate p)```
Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise).
`static boolean` ```isInCircleRobust(Coordinate a, Coordinate b, Coordinate c, Coordinate p)```
Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise).
`static DD` ```triAreaDDFast(Coordinate a, Coordinate b, Coordinate c)```
`static DD` ```triAreaDDSlow(DD ax, DD ay, DD bx, DD by, DD cx, DD cy)```
Computes twice the area of the oriented triangle (a, b, c), i.e., the area is positive if the triangle is oriented counterclockwise.
• ### Methods inherited from class java.lang.Object

`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`
• ### Constructor Detail

• #### TrianglePredicate

`public TrianglePredicate()`
• ### Method Detail

• #### isInCircleNonRobust

```public static boolean isInCircleNonRobust(Coordinate a,
Coordinate b,
Coordinate c,
Coordinate p)```
Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise). This test uses simple double-precision arithmetic, and thus may not be robust.
Parameters:
`a` - a vertex of the triangle
`b` - a vertex of the triangle
`c` - a vertex of the triangle
`p` - the point to test
Returns:
true if this point is inside the circle defined by the points a, b, c
• #### isInCircleNormalized

```public static boolean isInCircleNormalized(Coordinate a,
Coordinate b,
Coordinate c,
Coordinate p)```
Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise). This test uses simple double-precision arithmetic, and thus is not 100% robust. However, by using normalization to the origin it provides improved robustness and increased performance.

Based on code by J.R.Shewchuk.

Parameters:
`a` - a vertex of the triangle
`b` - a vertex of the triangle
`c` - a vertex of the triangle
`p` - the point to test
Returns:
true if this point is inside the circle defined by the points a, b, c
• #### isInCircleRobust

```public static boolean isInCircleRobust(Coordinate a,
Coordinate b,
Coordinate c,
Coordinate p)```
Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise). This method uses more robust computation.
Parameters:
`a` - a vertex of the triangle
`b` - a vertex of the triangle
`c` - a vertex of the triangle
`p` - the point to test
Returns:
true if this point is inside the circle defined by the points a, b, c
• #### isInCircleDDSlow

```public static boolean isInCircleDDSlow(Coordinate a,
Coordinate b,
Coordinate c,
Coordinate p)```
Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise). The computation uses `DD` arithmetic for robustness.
Parameters:
`a` - a vertex of the triangle
`b` - a vertex of the triangle
`c` - a vertex of the triangle
`p` - the point to test
Returns:
true if this point is inside the circle defined by the points a, b, c

```public static DD triAreaDDSlow(DD ax,
DD ay,
DD bx,
DD by,
DD cx,
DD cy)```
Computes twice the area of the oriented triangle (a, b, c), i.e., the area is positive if the triangle is oriented counterclockwise. The computation uses `DD` arithmetic for robustness.
Parameters:
`ax` - the x ordinate of a vertex of the triangle
`ay` - the y ordinate of a vertex of the triangle
`bx` - the x ordinate of a vertex of the triangle
`by` - the y ordinate of a vertex of the triangle
`cx` - the x ordinate of a vertex of the triangle
`cy` - the y ordinate of a vertex of the triangle
• #### isInCircleDDFast

```public static boolean isInCircleDDFast(Coordinate a,
Coordinate b,
Coordinate c,
Coordinate p)```

```public static DD triAreaDDFast(Coordinate a,
Coordinate b,
Coordinate c)```
• #### isInCircleDDNormalized

```public static boolean isInCircleDDNormalized(Coordinate a,
Coordinate b,
Coordinate c,
Coordinate p)```
• #### isInCircleCC

```public static boolean isInCircleCC(Coordinate a,
Coordinate b,
Coordinate c,
Coordinate p)```
Computes the inCircle test using distance from the circumcentre. Uses standard double-precision arithmetic.

In general this doesn't appear to be any more robust than the standard calculation. However, there is at least one case where the test point is far enough from the circumcircle that this test gives the correct answer.

``` LINESTRING
(1507029.9878 518325.7547, 1507022.1120341457 518332.8225183258,
1507029.9833 518325.7458, 1507029.9896965567 518325.744909031)
```
Parameters:
`a` - a vertex of the triangle
`b` - a vertex of the triangle
`c` - a vertex of the triangle
`p` - the point to test
Returns:
true if this point is inside the circle defined by the points a, b, c