Game maker studio 2 collision series#

In the broad phase of collision physics for video games we need to identify which pairs of rigid bodies might be colliding. In the next sections weвЂ™ll talk about some algorithms that can be used in the broad phase and narrow phase. It is a refinement step where we determine if the collisions are actually happening, and for each collision that is found, we compute the contact points that will be used to solve the collisions later. The narrow phase operates on the pairs of rigid bodies found by the broad phase that might be colliding. To achieve that, this phase generally uses space partitioning coupled with bounding volumes that establish an upper bound for collision. This step must be able to scale really well with the number of rigid bodies to make sure we stay well under the O( n 2) time complexity. The broad phase is responsible for finding pairs of rigid bodies that are potentially colliding, and excluding pairs that are certainly not colliding, from amongst the whole set of bodies that are in the simulation.

In order to optimize the collision detection process, we generally split it in two phases: broad phase and narrow phase. The number of pairwise tests increases quadratically with the number of bodies, and determining if two shapes, in arbitrary positions and orientations, are colliding is already not cheap. If we have n bodies in our simulation, the computational complexity of detecting collisions with pairwise tests is O( n 2), a number that makes computer scientists cringe. In the context of rigid body simulations, a collision happens when the shapes of two rigid bodies are intersecting, or when the distance between these shapes falls below a small tolerance. In the next, and final, installment, weвЂ™ll talk more about вЂњsolvingвЂќ these collisions to eliminate interpenetrations.ДЇor a review of the linear algebra concepts referred to in this article, you can refer to the linear algebra crash course in Part I. In Part II, we will cover the collision detection step, which consists of finding pairs of bodies that are colliding among a possibly large number of bodies scattered around a 2D or 3D world. This is where understanding collision physics is particularly important for game developers. In order to more realistically simulate the behavior of solid objects, we have to check if they collide with each other every time they move, and if they do, we have to do something about it, such as applying forces that change their velocities, so that they will move in the opposite direction. Without some additional work, the simulated rigid bodies can go right through each other, or вЂњinterpenetrateвЂќ, which is undesirable in the majority of cases. In that discussion, however, objects did not interact with each other. In Part I of this series, we explored rigid bodies and their motions.

Part III: Constrained Rigid Body Simulation Part I: An Introduction to Rigid Body Dynamics

Game maker studio 2 collision series#

returns whether two bodies are touchingДЇor(s = ep_body_first_shape(argument0, argument1) s!=0 s = ep_shape_next(argument0, argument1, s)) else if object1.object_index=obj_player and object_is_ancestor(object2.This is Part II of our three-part series on video game physics.

You can use this script to check whether two bodies are touching: // bodies_touch(world,body1_id,body2_id) Whenever two bodies collide, ExtremePhysics will create a contact automatically when you call ep_world_update_contacts. Collisions between existing bodiesД¬ollisions between existing bodies can be detected with contacts. If you use ExtremePhysics, it's usually better to use ExtremePhysics collision detection functions. This is because Game Maker calculates collisions based on the sprites, which is not very precise. If you use the build-in GM collision events or functions, the results won't always be correct.

But sometimes you might want to do something special when two bodies collide, for example destroy one of the bodies. ExtremePhysics handles collisions automatically, so usually you don't have to do anything when two bodies collide.