Merge pull request #1066 from nmaslarinos/circle_functions_bugfix

Circle functions bugfix

Author: tomvanmele

AUTHORS.md

@@ -34,3 +34,4 @@
 - Nizar Taha <<[email protected]>> [@nizartaha](https://github.com/nizartaha)
 - Gene Ting-Chun Kao <<[email protected]>> [@GeneKao](https://github.com/GeneKao)
 - Chen Kasirer <<[email protected]>> [@chenkasirer](https://github.com/chenkasirer)
+- Nickolas Maslarinos <<[email protected]>> [@nmaslarinos](https://github.com/nmaslarinos)

CHANGELOG.md

@@ -19,6 +19,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Added boolean operation operator overloads in `compas.geometry.Brep`
 * Added `format` task using `black` formatter.
 
+* Added a `test_intersection_circle_circle_xy` in the `test_intersections`
+
 ### Changed
 * Based all gltf data classes on `BaseGLTFDataClass`
 
@@ -27,6 +29,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Changed linter to `black`.
 * Automatically trigger `invoke format` during `invoke release`.
 
+* Fixed bug in `intersections.intersection_circle_circle_xy` where the Circle's Plane was accessed instead of the centre. 
+* Fixed bug in `_core.tangent` where the Circle's Plane was accessed instead of the centre.
+* Fixed the `test_tangent` to work with a properly defined circle
 ### Removed
 
 

src/compas/geometry/_core/tangent.py

@@ -2,7 +2,7 @@
 from __future__ import absolute_import
 from __future__ import division
 
-import math
+from math import sqrt
 
 
 __all__ = ["tangent_points_to_circle_xy"]
@@ -14,7 +14,7 @@ def tangent_points_to_circle_xy(circle, point):
     Parameters
     ----------
     circle : [plane, float] | :class:`~compas.geometry.Circle`
-        center, radius of the circle in the xy plane.
+        Plane and radius of the circle.
     point : [float, float] or [float, float, float] | :class:`~compas.geometry.Point`
         XY(Z) coordinates of a point in the xy plane.
 
@@ -26,25 +26,33 @@ def tangent_points_to_circle_xy(circle, point):
     Examples
     --------
     >>> from compas.geometry import allclose
-    >>> circle = (0, 0, 0), 1.0
+    >>> circle = ((0, 0, 0), (0, 0, 1)), 1.0
     >>> point = (2, 4, 0)
     >>> t1, t2 = tangent_points_to_circle_xy(circle, point)
     >>> allclose(t1, [-0.772, 0.636, 0.000], 1e-3)
     True
     >>> allclose(t2, [0.972, -0.236, 0.000], 1e-3)
     True
     """
-    m, r = circle[0], circle[1]
-    cx, cy = m[0], m[1]
-    px = point[0] - cx
-    py = point[1] - cy
+    plane, R = circle
+    center, _ = plane
 
-    a1 = r * (px * r - py * math.sqrt(px**2 + py**2 - r**2)) / (px**2 + py**2)
-    a2 = r * (px * r + py * math.sqrt(px**2 + py**2 - r**2)) / (px**2 + py**2)
+    cx, cy = center[:2]
+    px, py = point[:2]
 
-    b1 = (r**2 - px * a1) / py
-    b2 = (r**2 - px * a2) / py
+    dx = px - cx
+    dy = py - cy
 
-    p1 = [a1 + cx, b1 + cy, 0]
-    p2 = [a2 + cx, b2 + cy, 0]
-    return p1, p2
+    D = sqrt(dx**2 + dy**2)
+    L2 = D**2 - R**2
+
+    a = dx / D, dy / D
+    b = -a[1], a[0]
+
+    A = D - L2 / D
+    B = sqrt(R**2 - A**2)
+
+    t1 = cx + A * a[0] + B * b[0], cy + A * a[1] + B * b[1], 0
+    t2 = cx + A * a[0] - B * b[0], cy + A * a[1] - B * b[1], 0
+
+    return t1, t2

src/compas/geometry/intersections/intersections.py

@@ -893,9 +893,9 @@ def intersection_circle_circle_xy(circle1, circle2):
     Parameters
     ----------
     circle1 : [plane, float] | :class:`~compas.geometry.Circle`
-        Circle defined by a point, with at least XY coordinates, and a radius.
+        Circle defined by a plane, with at least XY coordinates, and a radius.
     circle2 : [plane, float] | :class:`~compas.geometry.Circle`
-        Circle defined by a point, with at least XY coordinates, and a radius.
+        Circle defined by a plane, with at least XY coordinates, and a radius.
 
     Returns
     -------
@@ -905,26 +905,35 @@ def intersection_circle_circle_xy(circle1, circle2):
         None otherwise.
 
     """
-    p1, r1 = circle1[0], circle1[1]
-    p2, r2 = circle2[0], circle2[1]
+    plane1, r1 = circle1
+    plane2, r2 = circle2
+    p1, n1 = plane1
+    p2, n2 = plane2
+    R = length_vector_xy(subtract_vectors_xy(p2, p1))
 
-    d = length_vector_xy(subtract_vectors_xy(p2, p1))
-
-    if d > r1 + r2:
+    if R > r1 + r2:
         return None
 
-    if d < fabs(r1 - r2):
+    if R < fabs(r1 - r2):
         return None
 
-    if (d == 0) and (r1 == r2):
+    if (R == 0) and (r1 == r2):
         return None
 
-    a = (r1 * r1 - r2 * r2 + d * d) / (2 * d)
-    h = (r1 * r1 - a * a) ** 0.5
-    cx2 = p1[0] + a * (p2[0] - p1[0]) / d
-    cy2 = p1[1] + a * (p2[1] - p1[1]) / d
-    i1 = ((cx2 + h * (p2[1] - p1[1]) / d), (cy2 - h * (p2[0] - p1[0]) / d), 0)
-    i2 = ((cx2 - h * (p2[1] - p1[1]) / d), (cy2 + h * (p2[0] - p1[0]) / d), 0)
+    x1, y1 = p1[:2]
+    x2, y2 = p2[:2]
+
+    cx = 0.5 * (x1 + x2)
+    cy = 0.5 * (y2 + y1)
+
+    R2 = R * R
+    R4 = R2 * R2
+
+    a = (r1 * r1 - r2 * r2) / (2 * R2)
+    b = 0.5 * sqrt(2 * (r1 * r1 + r2 * r2) / R2 - (r1 * r1 - r2 * r2) ** 2 / R4 - 1)
+
+    i1 = cx + a * (x2 - x1) + b * (y2 - y1), cy + a * (y2 - y1) + b * (x1 - x2), 0
+    i2 = cx + a * (x2 - x1) - b * (y2 - y1), cy + a * (y2 - y1) - b * (x1 - x2), 0
 
     return i1, i2
 

tests/compas/geometry/test_intersections.py

@@ -1,6 +1,7 @@
 from compas.geometry import allclose
 from compas.geometry import intersection_sphere_line
 from compas.geometry import intersection_plane_circle
+from compas.geometry import intersection_circle_circle_xy
 
 
 def test_intersection_sphere_line():
@@ -17,3 +18,11 @@ def test_intersection_plane_circle():
     ipt1, ipt2 = intersection_plane_circle(plane, circle)
     assert allclose(ipt1, (-6.165, 7.000, 0.000), tol=1e-3)
     assert allclose(ipt2, (12.165, 7.000, 0.000), tol=1e-3)
+
+
+def test_intersection_circle_circle_xy():
+    circle1 = ((0.0, 0.0, 0.0), (0, 0, 1)), 10.0
+    circle2 = ((3.0, 7.0, 0.0), (0, 0, 1)), 10.0
+    ipt1, ipt2 = intersection_circle_circle_xy(circle1, circle2)
+    assert allclose(ipt1, (9.999, -0.142, 0.000), tol=1e-3)
+    assert allclose(ipt2, (-6.999, 7.142, 0.000), tol=1e-3)

tests/compas/geometry/test_tangent.py

@@ -3,8 +3,8 @@
 
 
 def test_tangent_points_to_circle_xy():
-    circle = (0, 0, 0), 1.0
-    point = (2, 4, 0)
+    circle = ((0.0, 0.0, 0.0), (0.0, 0.0, 1.0)), 1.0
+    point = (2.0, 4.0, 0.0)
     t1, t2 = tangent_points_to_circle_xy(circle, point)
     assert allclose(t1, (-0.772, 0.636, 0.000), tol=1e-3)
     assert allclose(t2, (0.972, -0.236, 0.000), tol=1e-3)