Agent collisions about mesa-geo

[wang-boyu]

This would be a useful feature for certain cases, and involve a physics engine in order to do collision detection. Looks like similar functionalities have been added into MASON (a Java ABM library) as an extension:

• https://docplayer.net/22323269-Building-a-2d-physics-engine-for-mason-christian-thompson-gmu-cs-798.html
• https://cs.gmu.edu/~eclab/projects/mason/extensions/physics2d/PhysicsEnginePresentation.pdf
• source code: https://github.com/eclab/mason/tree/master/contrib/physics2d

For us, there should be several 2d physics engines available in Python. I'm wondering whether it makes more sense to have it as a separate Mesa extension, like the case for MASON.

[rht]

For us, there should be several 2d physics engines available in Python.

Yeah, there should be some that already exist.

[wang-boyu]

As a workaround, we can randomly assign agents' location to avoid them standing on top of each other. These are demonstrated in some example models in this repo:

raster data model
In the Population model, to assign random positions to people within the same raster cell:

mesa-geo/examples/population/population/model.py

Lines 22 to 32 in e6be96d

	def set_random_world_coord(self):
	world_coord_point = Point(
	self.model.space.population_layer.transform * self.img_coord
	)
	random_world_coord_x = world_coord_point.x + np.random.uniform(
	-self.MOBILITY_RANGE_X, self.MOBILITY_RANGE_X
	)
	random_world_coord_y = world_coord_point.y + np.random.uniform(
	-self.MOBILITY_RANGE_Y, self.MOBILITY_RANGE_Y
	)
	self.geometry = Point(random_world_coord_x, random_world_coord_y)

vector data model
In the GeoSchelling (Points & Polygons) model, to assign random positions to people within the same polygon:

mesa-geo/examples/geo_schelling_points/geo_schelling_points/space.py

Lines 27 to 32 in e6be96d

	def add_person_to_region(self, person, region_id):
	person.region_id = region_id
	person.geometry = self._id_region_map[region_id].random_point()
	self._id_region_map[region_id].add_person(person)
	super().add_agents(person)
	self.num_people += 1

As mentioned above, physics engines won't be implemented within mesa-geo for now. Hence I'm closing this issue as won't fix. But pls feel free to continue the discussion here. We can also convert this to a discussion if needed.