How do you design collision detection for different genres or platforms of mobile games?

1 2D vs 3D collision detection

One of the first decisions you need to make when designing collision detection is whether your game is 2D or 3D. This affects the complexity and performance of your collision detection system, as well as the tools and libraries you can use. Generally, 2D collision detection is simpler and faster than 3D collision detection, as you only need to check the overlap of shapes on a single plane. However, 3D collision detection requires more calculations and data structures to handle the depth and orientation of objects in a 3D space. You can use frameworks like Unity or Unreal Engine to handle 3D collision detection for you, or you can implement your own algorithms using concepts like bounding volumes, ray casting, or spatial partitioning.

2 Discrete vs continuous collision detection

Another important factor to consider when designing collision detection is whether your game uses discrete or continuous collision detection. Discrete collision detection checks for collisions at fixed intervals, such as every frame or every update cycle. Continuous collision detection checks for collisions along the entire trajectory of an object, such as a bullet or a fast-moving character. Discrete collision detection is easier and more efficient to implement, but it can result in missed collisions or tunneling effects if the objects move too fast or the intervals are too large. Continuous collision detection is more accurate and realistic, but it can be more computationally intensive and complex to implement. You can use hybrid approaches that combine discrete and continuous collision detection for different types of objects or scenarios, depending on your game's needs and limitations.

3 Collision response and physics

Collision detection is not only about detecting collisions, but also about responding to them. Depending on the genre and platform of your game, you may want different types of collision response and physics for your objects. For example, in a platformer game, you may want simple collision response that prevents objects from overlapping and allows them to bounce or slide off each other. In a racing game, you may want more realistic collision response that simulates the impact, damage, and friction of the vehicles. In a puzzle game, you may want more creative collision response that triggers events, animations, or sounds when objects collide. You can use physics engines like Box2D, PhysX, or Bullet to handle collision response and physics for you, or you can implement your own logic and rules using concepts like impulse, momentum, or restitution.

4 Collision optimization and debugging

Collision detection can be a performance bottleneck and a source of bugs in mobile game development, especially if there are many objects, complex shapes, or fast movements. To ensure the system runs smoothly and correctly on target devices, you need to optimize and debug your collision detection system. Common techniques and tools for this include using simple shapes or bounding boxes for collision detection instead of detailed meshes or sprites, reducing the number of collision checks with spatial partitioning, broad-phase and narrow-phase algorithms, or collision layers and masks, implementing collision events or callbacks instead of polling for collisions every frame or update, using visual aids or debug modes to display the collision shapes, volumes, or rays of objects, and using profilers or performance monitors to measure the CPU and memory usage of your collision detection system.

5 Collision design and feedback

Collision detection is not only a technical feature, but also a design feature that affects the gameplay and user experience of your mobile game. Therefore, it’s important to consider the genre, platform, and audience when designing the collision detection system. You should think about how collision detection fits with the game's theme, style, and mechanics, as well as how it affects the difficulty, challenge, and fun of your game. Additionally, consider how collision detection supports or hinders the player's control, input, and feedback. Furthermore, look into how it varies or adapts to different levels, modes, or situations in your game. Lastly, consider how it communicates or informs the player about the game's state, rules, or goals.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?