Here is some information about movement system in HONK which I'll use in my another project One Spear, One Kill.

First of all, it based on this tutorial - A Comprehensive Guide To Time Dilation. Even though there is an example project, I've written my own system, which I use everywhere in the game.

Scripts

If I need to move something with acceleration or deceleration I will add in Step Event these scripts: 1. MoveObject; 2. CalculateAcceleratedVelocity; 3. CalculateDeceleratedVelocity; 4. CalculateConstantMovement;

MoveObject

It's a straightforward script, but because of using this system everywhere wherever I want, I keep it so simple. As different things require different calculations. For instance, I use both CalculateAcceleratedVelocity and CalculateDeceleratedVelocity in the player object; on the other hand, in projectiles, I use only one of these things at the same time.

It's very important to call this script before velocity calculations.

```gml //------------// // MoveObject // //------------//

// @param isConstant

var _isConstant = argument0;

if (_isConstant) { x += velocityX * global.TimeFactor; y += velocityY * global.TimeFactor; } else { x += velocityX; y += velocityY; } ```

CalculateAceleratedVelocity

This script calculates velocity while an object is accelerating.

``` //------------------------------// // CalculateAcceleratedVelocity // //------------------------------//

/// @param direction /// @param velocityCurrent /// @param velocityMax /// @param acceleration

var _targetDirection = argument0; var _velocityCurrent = argument1; var _velocityMax = argument2; var _acceleration = argument3;

//Delta X and Y calculations var positionDelta = global.TimeFactor * _velocityCurrent + (0.5 * sqr(global.TimeFactor) * _acceleration); _velocityCurrent = min(velocityCurrent + acceleration * global.TimeFactor, _velocityMax); velocityX = lengthdirx(positionDelta, _targetDirection); velocityY = lengthdiry(_positionDelta, _targetDirection);

return _velocityCurrent; ```

CalculateDeceleratedVelocity

This script calculates velocity while an object is decelerating.

``` //------------------------------// // CalculateDeceleratedVelocity // //------------------------------//

/// @param direction /// @param velocityCurrent /// @param friction

var _targetDirection = argument0; var _velocityCurrent = argument1; var _friction = argument2;

var addX = _friction * sign(velocityCurrent); var positionDelta = global.TimeFactor * _velocityCurrent + (0.5 * sqr(global.TimeFactor) * _addX); _velocityCurrent = max(velocityCurrent - friction * global.TimeFactor, 0); velocityX = lengthdirx(positionDelta, _targetDirection); velocityY = lengthdiry(_positionDelta, _targetDirection);

return _velocityCurrent; ```

CalculateConstantVelocity

In case when I need to move something with a constant velocity I use this script.

``` //---------------------------// // CalculateConstantVelocity // //---------------------------//

/// @param Velocity /// @param direction

var _velocity = argument0; var _direction = argument1;

velocityX = lengthdirx(velocity, direction); velocityY = lengthdiry(_velocity, _direction); ```

Collisions

And what about collisions? I use a classic script for checking collisions, and I place it after all movement calculations.

But be aware, I don't use this script to execute other code, e.g. destroying projectiles, dealing damage etc.

``` //----------------// // CheckCollision // //----------------//

// @param object

var _object = argument0;

// Collision X if (placemeeting(x + velocityX, y, _object)) { while (!placemeeting(x + sign(velocityX), y, _object)) { x += sign(velocityX); } velocityX = 0; }

// Collision Y if (placemeeting(x, y + velocityY, _object)) { while (!placemeeting(x, y + sign(velocityY), _object)) { y += sign(velocityY); } velocityY = 0; } ```

Thank you for reading, feel free to ask questions and give feedback.

Original devlog