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collision_detection.py
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collision_detection.py
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import numpy as np
def checkPolyCircleIntersecting(poly, circleX, circleY, circleR):
"""
Checks whether a polygon intersects a circle
Parameters
----------
poly : np.array(N,2)
Ordered list of 2D vertices defining a convex polygon
circleX, circleY : float
Circle centre coordinates
circleR : float
Circle radius
Returns
-------
bool
True - intersecting
False - not intersecting
"""
# Check if any line in poly collides with the circle
for i in range(len(poly)):
vStartIdx = i
# print("vStartIdx: ", vStartIdx)
vEndIdx = (i + 1) % len(poly)
# print("vEndIdx: ", vEndIdx)
# Return intersecting True on first line collision
if checkLineCircleIntersecting(poly[vStartIdx,0], poly[vStartIdx,1],
poly[vEndIdx,0], poly[vEndIdx,1],
circleX, circleY, circleR):
return True
# No collision if all edges checked
return False
def checkLineCircleIntersecting(X1, Y1, X2, Y2, circleX, circleY, circleR):
"""
Checks whether a line intersects a circle
Parameters
----------
X1, Y1, X2, Y2: float
Start and end of line coordinates
circleX, circleY : float
Circle centre coordinates
circleR : float
Circle radius
Returns
-------
bool
True - intersecting
False - not intersecting
"""
vStart = np.array([X1, Y1])
#print("vStart: ", vStart)
vEnd = np.array([X2, Y2])
#print("vEnd: ", vEnd)
centre = np.array([circleX, circleY])
line = vEnd - vStart
# Check whether either end is inside circle
# if np.linalg.norm([vStart[0]-circleX, vStart[1]-circleY]) < circleR:
# return True
# elif np.linalg.norm([vEnd[0]-circleX, vEnd[1]-circleY]) < circleR:
# return True
# Get projection size from edge start to circle centre onto edge
proj = np.dot(centre - vStart, line)
#print("proj: ", proj)
projFraction = proj/np.dot(line, line)
#print("projFraction: ", projFraction)
# if projection fraction is < 0 or > 1, closest point is off line (no collision)
if projFraction < 0 or projFraction > 1:
return False
# Closest point on line
vClose = vStart + projFraction*line
# Distance closest point to centre
distClose = np.linalg.norm(centre - vClose)
if distClose < circleR:
return True
else:
return False
def checkPolysIntersecting(polyA, polyB):
"""
Checks whether convex polygons are intersecting by checking
if no separation axis from A to B and B to A.
Parameters
----------
polyA : np.array(N,2)
Ordered list of 2D vertices defining a convex polygon
polyB : np.array(N,2)
Ordered list of 2D vertices defining a convex polygon
Returns
-------
bool
True - polygons are intersecting
False - polgons are not intersecting
"""
return checkNoSeparation(polyA, polyB) and checkNoSeparation(polyB, polyA)
def checkNoSeparation(polyA, polyB):
"""
Checks whether separation axis is detected from polyA to polyB
(ie checking vertices of A & B against edges of A)
Parameters
----------
polyA : np.array(N,2)
Ordered list of 2D vertices defining a convex polygon
polyB : np.array(N,2)
Ordered list of 2D vertices defining a convex polygon
Returns
-------
bool
True - no separation from A to B
False - separation from A to B
"""
# Calculate orthogonal axis for each edge in A
for i in range(len(polyA)):
vStartIdx = i
# print("vStartIdx: ", vStartIdx)
vEndIdx = (i + 1) % len(polyA)
# print("vEndIdx: ", vEndIdx)
edge = polyA[vEndIdx,:] - polyA[vStartIdx,:]
# print("edge: ", edge)
orthAxis = np.array([-edge[1], edge[0]])
# print("orthAxis: ", orthAxis)
orthAxisNorm = np.linalg.norm(orthAxis)
# print("orthAxisNorm: ", orthAxisNorm)
# Check minimum projection for points in A
minProjA = float('inf')
maxProjA = float('-inf')
for v in polyA:
# print("v: ", v)
proj = np.dot(v,orthAxis)/orthAxisNorm
# print("proj: ", proj)
if proj < minProjA:
minProjA = proj
# print("minProjA: ", minProjA)
if proj > maxProjA:
maxProjA = proj
# print("maxProjA: ", maxProjA)
# Check minimum projection for points in B
minProjB = float('inf')
maxProjB = float('-inf')
for v in polyB:
# print("v: ", v)
proj = np.dot(v,orthAxis)/orthAxisNorm
# print("proj: ", proj)
if proj < minProjB:
minProjB = proj
# print("minProjB: ", minProjB)
if proj > maxProjB:
maxProjB = proj
# print("maxProjB: ", maxProjB)
# Condition for overlap
if (maxProjA > minProjB) and (minProjA < maxProjB):
pass
else:
# If no overlap detected, exit early
## DEBUG
#print("StartIdx, EndIdx, ", vStartIdx, vEndIdx)
#print("Edge, OrthAxis, ", edge, orthAxis)
#print("minProjA: ", minProjA)
#print("maxProjA: ", maxProjA)
#print("minProjB: ", minProjB)
#print("maxProjB: ", maxProjA)
## DEBUG
return False
# If all edges checked without separation detected,
return True