77 lines
2.9 KiB
Python
77 lines
2.9 KiB
Python
from dataclasses import dataclass
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from itertools import combinations
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import pygame as pg
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from collider import *
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from transform import Transform
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@dataclass
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class RigidBody:
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transform: Transform
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collider: BaseCollider
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velocity: pg.Vector2
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angular_velocity: float = 0
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mass: float = 1.0
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restitution: float = 0.5
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@property
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def inv_mass(self) -> float:
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return 0.0 if self.mass == 0.0 else 1/self.mass
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@property
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def moment_of_inertia(self) -> float:
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return 0.0 if self.mass == 0.0 else self.collider.moment_of_inertia(self.mass)
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@property
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def inv_moment_of_inertia(self) -> float:
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return 0.0 if self.mass == 0.0 else 1/self.moment_of_inertia
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class PhysicsSystem:
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def __init__(self, gravity: int = 250):
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self.bodies: list[RigidBody] = []
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self.gravity = pg.Vector2(0,gravity)
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def add_body(self, body: RigidBody) -> None:
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self.bodies.append(body)
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def update(self, dt: float):
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g = self.gravity * dt
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for body in self.bodies:
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if body.mass != 0.0:
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body.velocity += g
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body.transform.position += dt * body.velocity
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body.transform.rotation += dt * body.angular_velocity
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for a, b in combinations(self.bodies, 2):
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if collision := intersect(a.collider, b.collider, a.transform, b.transform):
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self.resolve_collision(a, b, collision)
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def resolve_collision(self, a: RigidBody, b: RigidBody, collision: ColliderContact) -> None:
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SLACK=0.2
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correction = collision.penetration / (a.inv_mass + b.inv_mass) * SLACK * collision.normal
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if a.mass != 0.0:
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a.transform.position += correction
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if b.mass != 0.0:
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b.transform.position -= correction
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for point in collision.points:
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r_a = point - a.transform.position
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r_b = point - b.transform.position
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w_cross_r_a = pg.Vector2(-r_a.y * a.angular_velocity, r_a.x * a.angular_velocity) #omega is not encoded as a vector, so we pretend it is
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w_cross_r_b = pg.Vector2(-r_b.y * b.angular_velocity, r_b.x * b.angular_velocity)
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v_rel = a.velocity + w_cross_r_a - b.velocity - w_cross_r_b
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restitution = a.restitution * b.restitution
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impulse = -(1+restitution)*(v_rel.dot(collision.normal))\
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/ (a.inv_mass + b.inv_mass + (r_a.cross(collision.normal)**2 * a.inv_moment_of_inertia)\
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+ (r_b.cross(collision.normal)**2 * b.inv_moment_of_inertia)) / len(collision.points)
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a.velocity += collision.normal*impulse*a.inv_mass
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b.velocity -= collision.normal*impulse*b.inv_mass
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a.angular_velocity += (r_a.cross(impulse*collision.normal)) * a.inv_moment_of_inertia
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b.angular_velocity -= (r_b.cross(impulse*collision.normal)) * b.inv_moment_of_inertia
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