Physics

Collision on a Tilemap In a tile-based game, collision detection isn’t just about object-to-object overlap; it’s about checking if a moving sprite is trying to occupy a tile marked as solid (e.g., a wall, water, or rock). The Core Logic: Before updating a sprite’s position, check the Tile ID at the new (target) location. Step 1: Converting Sprite Position to Tile Index The first challenge is converting the sprite’s precise pixel coordinates (X, Y) into the coarse array index needed to read the tilemap. ...

The Need for Resolution Collision Detection (Part 26) only tells you that two objects overlap. Collision Resolution is the logic that moves the objects apart and adjusts their speed (velocity) so that they don’t overlap in the next frame. Without resolution, sprites will get stuck inside walls. Step 1: Backtracking (The Safest Move) The most reliable way to resolve an overlap is to simply move the collided object back to its previous, non-colliding position. ...

The Concept of Velocity and Gravity To make a sprite move realistically (fall, jump), we need two new variables in our sprite data structure: Velocity (DY): The current speed and direction of the sprite on the Y-axis. Gravity: A constant value that is continually added to the velocity every frame, causing the sprite to accelerate downward. The Calculation: The physics update is done by: Velocity ← Velocity + Gravity Y-Coordinate ← Y-Coordinate + Velocity Updating Velocity with Gravity We will need a new field in our sprite descriptor (e.g., offset +A for an 8-bit velocity) and a constant for gravity. ...