Source code for pymunk.shape_filter

from collections import namedtuple

[docs]class ShapeFilter(namedtuple("ShapeFilter", ['group', 'categories', 'mask'])): """ Pymunk has two primary means of ignoring collisions: groups and category masks. Groups are used to ignore collisions between parts on a complex object. A ragdoll is a good example. When jointing an arm onto the torso, you'll want them to allow them to overlap. Groups allow you to do exactly that. Shapes that have the same group don't generate collisions. So by placing all of the shapes in a ragdoll in the same group, you'll prevent it from colliding against other parts of itself. Category masks allow you to mark which categories an object belongs to and which categories it collides with. For example, a game has four collision categories: player (0), enemy (1), player bullet (2), and enemy bullet (3). Neither players nor enemies should not collide with their own bullets, and bullets should not collide with other bullets. However, players collide with enemy bullets, and enemies collide with player bullets. ============= =============== ==================== Object Object Category Category Mask ============= =============== ==================== Player 0b00001 (1) 0b11000 (4, 5) Enemy 0b00010 (2) 0b01110 (2, 3, 4) Player Bullet 0b00100 (3) 0b10001 (1, 5) Enemy Bullet 0b01000 (4) 0b10010 (2, 5) Walls 0b10000 (5) 0b01111 (1, 2, 3, 4) ============= =============== ==================== Note that in the table the categories and masks are written as binary values to clearly show the logic. To save space only 5 digits are used. The default type of categories and mask in ShapeFilter is an unsigned int, with a resolution of 32 bits. That means that the you have 32 bits to use, in binary notation that is `0b00000000000000000000000000000000` to `0b11111111111111111111111111111111` which can be written in hex as `0x00000000` to 0xFFFFFFFF`. Everything in this example collides with walls. Additionally, the enemies collide with each other. By default, objects exist in every category and collide with every category. Objects can fall into multiple categories. For instance, you might have a category for a red team, and have a red player bullet. In the above example, each object only has one category. The default type of categories and mask in ShapeFilter is unsigned int which has a resolution of 32 bits on most systems. There is one last way of filtering collisions using collision handlers. See the section on callbacks for more information. Collision handlers can be more flexible, but can be slower. Fast collision filtering rejects collisions before running the expensive collision detection code, so using groups or category masks is preferred. Example of how category and mask can be used to filter out player from enemy object: >>> import pymunk >>> s = pymunk.Space() >>> player_b = pymunk.Body(1,1) >>> player_c = pymunk.Circle(player_b, 10) >>> s.add(player_b, player_c) >>> player_c.filter = pymunk.ShapeFilter(categories=0b1) >>> hit = s.point_query_nearest((0,0), 0, pymunk.ShapeFilter()) >>> hit != None True >>> filter = pymunk.ShapeFilter(mask=pymunk.ShapeFilter.ALL_MASKS ^ 0b1) >>> hit = s.point_query_nearest((0,0), 0, filter) >>> hit == None True >>> enemy_b = pymunk.Body(1,1) >>> enemy_c = pymunk.Circle(enemy_b, 10) >>> s.add(enemy_b, enemy_c) >>> hit = s.point_query_nearest((0,0), 0, filter) >>> hit != None True """ __slots__ = () ALL_CATEGORIES = 0xffffffff ALL_MASKS = 0xffffffff def __new__(cls, group = 0, categories = 0xffffffff, mask = 0xffffffff): self = super(ShapeFilter, cls).__new__(cls, group, categories, mask) return self