def reflect( self, x, y ):
''' Calculates reflection between two circles. Returns the resulting momentum vector.
Takes the position of the reflection point as argument.
Test:
>>> from data import circle
>>> from data import vector2d
>>> c1 = circle.Circle()
>>> c1.position.x = -4
>>> c1.position.y = 2
>>> c1.radius = 2
>>> c1.momentum = vector2d.Vector2d( 4, 2 )
>>> c2 = circle.Circle()
>>> c2.position.x = 0
>>> c2.position.y = 2
>>> c2.radius = 2
>>> x = -2
>>> y = 2
>>> reflector = CircleCircleReflector( c1, c2 )
>>> v = reflector.reflect( x, y )
>>> print( '{0:.2f}, {1:.2f}'.format(v.x, v.y) )
-4.00, 2.00
'''
# Move reflection point to origin.
reflectionX = x - self._circle2.position.x
reflectionY = y - self._circle2.position.y
# Prepare comparison.
epsilon = 0.001
# Default values are used it the tangent line is vertical.
pointX1 = reflectionX
pointY1 = -1
pointX2 = reflectionX
pointY2 = 1
# Calculate tangent line y = mx + b
if not comparison.floatEqual( reflectionY, 0, epsilon ):
# Tangent line is perpendicular to the radius, so it's slope m will be a negative reciprocal
# of the slope of the line intersecting the reflection point.
m = -(reflectionX / reflectionY)
# Find b with the slope and the reflection point. Default value is used if tangent line is
# horizontal.
b = reflectionY
if not comparison.floatEqual( reflectionX, 0, epsilon ):
b = reflectionY / (m * reflectionX)
# Calculate tangent line points left and right of reflection point.
pointX1 = reflectionX - 1
pointY1 = m * pointX1 + b
pointX2 = reflectionX + 1
pointY2 = m * pointX2 + b
# Calculate result.
x, y = vector.reflectAtLine( self._circle1.momentum.x, self._circle1.momentum.y,
pointX1, pointY1, pointX2, pointY2 )
return vector2d.Vector2d( x, y )
def reflect( self, x, y ):
''' Calculates reflection between two circles. Returns the resulting momentum vector.
Takes the position of the reflection point as argument.
Test:
>>> from data import circle
>>> from data import rect
>>> from data import vector2d
>>> c = circle.Circle()
>>> c.position.x = -4
>>> c.position.y = 2
>>> c.radius = 2
>>> c.momentum = vector2d.Vector2d( 4, 2 )
>>> r = rect.Rect()
>>> r.position.x = 0
>>> r.position.y = 2
>>> r.width = 4
>>> r.height = 4
>>> x = -2
>>> y = 2
>>> reflector = CircleRectReflector( c, r )
>>> v = reflector.reflect( x, y )
>>> print( '{0:.2f}, {1:.2f}'.format(v.x, v.y) )
-4.00, 2.00
'''
# Calculate values of all four points of the rectangle without rotation.
heightHalf = self._rect.height * 0.5
widthHalf = self._rect.width * 0.5
xPlus = widthHalf
xMinus = -widthHalf
yPlus = heightHalf
yMinus = -heightHalf
# Rotate reflection point back and move to origin.
rotatedX = rotation.rotateX( x - self._rect.position.x,
y - self._rect.position.y,
-self._rect.angle )
rotatedY = rotation.rotateY( x - self._rect.position.x,
y - self._rect.position.y,
-self._rect.angle )
# Prepare comparison.
pointX1 = 0
pointY1 = 0
pointX2 = 0
pointY2 = 0
left, up, right = range(3)
dists = []
dists.append( py.pointToLineDistance(rotatedX, rotatedY, xMinus, yMinus, xMinus, yPlus) )
dists.append( py.pointToLineDistance(rotatedX, rotatedY, xMinus, yPlus, xPlus, yPlus) )
dists.append( py.pointToLineDistance(rotatedX, rotatedY, xPlus, yMinus, xPlus, yPlus) )
dists.append( py.pointToLineDistance(rotatedX, rotatedY, xMinus, yMinus, xPlus, yMinus) )
line = dists.index( min(dists) )
# Left.
if line is left:
pointX1 = xMinus
pointY1 = yMinus
pointX2 = xMinus
pointY2 = yPlus
# Up.
elif line is up:
pointX1 = xMinus
pointY1 = yPlus
pointX2 = xPlus
pointY2 = yPlus
# Right.
elif line is right:
pointX1 = xPlus
pointY1 = yMinus
pointX2 = xPlus
pointY2 = yPlus
# Down.
else:
pointX1 = xMinus
pointY1 = yMinus
pointX2 = xPlus
pointY2 = yMinus
# Rotate line points.
rotatedX1 = rotation.rotateX( pointX1, pointY1, self._rect.angle ) + self._rect.position.x
rotatedY1 = rotation.rotateY( pointX1, pointY1, self._rect.angle ) + self._rect.position.y
rotatedX2 = rotation.rotateX( pointX2, pointY2, self._rect.angle ) + self._rect.position.x
rotatedY2 = rotation.rotateY( pointX2, pointY2, self._rect.angle ) + self._rect.position.y
# Calculate result.
x, y = vector.reflectAtLine( self._circle.momentum.x, self._circle.momentum.y,
rotatedX1, rotatedY1, rotatedX2, rotatedY2 )
return vector2d.Vector2d( x, y )
