# xSGE Path
# Copyright (c) 2014 Julian Marchant <onpon4@riseup.net>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
This module provides paths for the SGE. Paths are used to make objects
move in a certain way.
"""
from __future__ import division
from __future__ import absolute_import
from __future__ import print_function
from __future__ import unicode_literals
import math
import sge
__all__ = ["Path"]
[docs]class Path(sge.Object):
"""
Class for paths: objects which define movement patterns for other
objects. Paths are defined as a series of points for an object to
follow.
This class is derived from :class:`sge.Object` and inherits all of
that class's attributes and methods.
.. note::
:meth:`event_step` is used to implement path-following behavior.
Keep this in mind if you derive a class from this one.
.. attribute:: points
A list of the points that make up the path relative to the
position of the path in the room, excluding the first point.
Each point should be a tuple in the form ``(x, y)``, where x is
the horizontal location and y is the vertical location. The
first point is always ``(0, 0)``, which is why it is not included
in this list.
"""
def __init__(self, x, y, points=(), z=0, sprite=None, visible=False,
active=True, checks_collisions=False, tangible=False,
bbox_x=None, bbox_y=None, bbox_width=None, bbox_height=None,
regulate_origin=False, collision_ellipse=False,
collision_precise=False, xvelocity=0, yvelocity=0,
image_index=0, image_origin_x=None, image_origin_y=None,
image_fps=None, image_xscale=1, image_yscale=1,
image_rotation=0, image_alpha=255, image_blend=None):
super(Path, self).__init__(
x, y, z=z, sprite=sprite, visible=visible, active=active,
checks_collisions=checks_collisions, tangible=tangible,
bbox_x=bbox_x, bbox_y=bbox_y, bbox_width=bbox_width,
bbox_height=bbox_height, regulate_origin=regulate_origin,
collision_ellipse=collision_ellipse,
collision_precise=collision_precise, xvelocity=xvelocity,
yvelocity=yvelocity, image_index=image_index,
image_origin_x=image_origin_x, image_origin_y=image_origin_y,
image_fps=image_fps, image_xscale=image_xscale,
image_yscale=image_yscale, image_rotation=image_rotation,
image_alpha=image_alpha, image_blend=image_blend)
self.points = list(points)
self.__objects = {}
self.__delta = 0
[docs] def follow_start(self, obj, speed, accel=None, decel=None, loop=0):
"""
Cause ``obj`` to start following this path at the speed
indicated by ``speed``.
While path objects have a location within the room, this
location has no bearing on how objects following the path move.
Movement is determined relative to the location of the object
following the path when it started, not the location of the
path.
By default, the object follows the path at a constant speed.
If ``accel`` or ``decel`` is set to a value other than
:const:`None`, the object will instead accelerate or decelerate,
respectively, by that amount each frame on each segment of the
path.
``loop`` indicates the number of times the object should follow
the path after it does so the first time. For example, if set
to ``2``, the object will follow the path a total of 3 times.
Set to :const:`None` to loop indefinitely.
.. note::
Acceleration and deceleration does not work with delta
timing. This is a simple consequence of the way delta timing
works; it is not possible to perfectly predict how much to
accelerate or decelerate to achieve the desired effect, and
to predict this even decently requires control over the
actual movement, which paths don't have.
"""
self.__objects[id(obj)] = [obj, speed, accel, decel, obj.x, obj.y,
loop, 0]
[docs] def follow_stop(self, obj):
"""Cause ``obj`` to stop following this path."""
i = id(obj)
if i in self.__objects:
del self.__objects[i]
[docs] def event_follow_end(self, obj):
"""
Called when an object, indicated by ``obj``, finishes following
the path.
"""
pass
def event_step(self, time_passed, delta_mult):
self.__delta = (self.__delta % 1) + delta_mult
for i in list(self.__objects.keys()):
(obj, speed, accel, decel, start_x, start_y, loop,
dest) = self.__objects[i]
dp = self.points[dest]
dx = dp[0] + start_x
dy = dp[1] + start_y
if math.hypot(dx - obj.x, dy - obj.y) < obj.speed:
dest += 1
obj.speed = 0
if dest < len(self.points):
dp = self.points[dest]
dx = dp[0] + start_x
dy = dp[1] + start_y
xdist = dx - obj.x
ydist = dy - obj.y
dist = math.hypot(xdist, ydist)
obj.move_direction = math.degrees(math.atan2(-ydist, xdist))
deceling = False
if decel:
d = obj.speed
decel_dist = 0
while d > 0:
d -= decel
decel_dist += d
if dist <= decel_dist:
obj.speed = max(0, obj.speed - decel)
deceling = True
if not deceling:
if accel and obj.speed < speed:
obj.speed = min(speed, obj.speed + accel)
else:
obj.speed = speed
self.__objects[i] = [obj, speed, accel, decel, start_x,
start_y, loop, dest]
else:
self.follow_stop(obj)
if loop is None:
self.follow_start(obj, speed, accel, decel, None)
elif loop > 0:
self.follow_start(obj, speed, accel, decel, loop - 1)
else:
self.event_follow_end(obj)