Question: How do you handle new collision events in GameMaker?


In GameMaker, collisions are a fundamental part of many games, allowing you to detect when objects interact with each other. When dealing with new collisions, you typically want to handle two main aspects: collision detection and collision response.

Collision Detection

Collision detection is the process by which GameMaker determines that two instances (objects) have intersected or come into contact within the game world. This can be managed using built-in functions or custom code for more complex scenarios.

Built-in Functions:

GameMaker provides several functions for handling collisions:

  • place_meeting(x, y, obj) : Checks if the instance would collide with an object (obj) at a given position (x, y).
  • instance_place(x, y, obj) : Returns the instance id of the obj at the position if a collision would occur, otherwise it returns noone.
  • collision_rectangle(...) : Checks for a collision within a defined rectangle area.
  • collision_circle(...) : Checks for a collision within a defined circular area.
  • collision_point(...) : Checks for a collision at a specific point.

These are just a few examples; there's a variety of collision functions available depending on the shape and type of collision you need.

Custom Collision Detection:

For more complex shapes or behaviors, you might create your own collision detection system using masks or precise pixel-perfect collision checks.

// Example of a custom bounding box collision check if (bbox_right > other.bbox_left && bbox_left < other.bbox_right && bbox_bottom > other.bbox_top && bbox_top < other.bbox_bottom) { // Collision has occurred }

Collision Response

Once a collision is detected, responding to it appropriately depends on the game mechanics. You may want to bounce off an object, stop movement, take damage, or any number of actions.

Here’s a simple example of changing direction upon collision:

// Assume this code is in the Step event of a moving object if (place_meeting(x + hspeed, y + vspeed, obj_wall)) { // Reverse direction hspeed = -hspeed; vspeed = -vspeed; } else { // Apply movement if no collision x += hspeed; y += vspeed; }

New Collision System in GameMaker Studio 2.3+

With the introduction of GameMaker Studio 2.3, there have been no revolutionary changes directly to how collisions are handled. However, enhancements such as new GML functionalities and sequence animations can affect how you approach designing and programming collisions.

Best Practices

  • Use collision layers to organize which objects should check for collisions against each other.
  • Keep your collision masks simple to optimize performance, especially if you are checking collisions every step.
  • Consider using spatial partitioning or grid-based collision checking for large numbers of instances to keep your game running smoothly.

Handling collisions effectively in GameMaker requires understanding these basic concepts and knowing when to apply the various functions and techniques available within the engine.

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