A parent based move and collide platformer system with moving solids made for GameMaker. Based on Celeste and TowerFall Physics
This system includes:
- Simple parenting system for easy implementation in your project
- Many actors simultaneously interacting with many moving solids
- Custom collision event definition
Bonus: Solids and actors can be customized to behave how you want! The demo project includes examples of a player actor and two different kinds of moving solids.
- Drag and drop the yymps file into your project to import the parent objects and utility scripts.
- Enable 'Compatibility Mode' for collisions in the Main Project Settings of your GameMaker project.
- Set the parent object of your Solids to o_solid (eg: walls and moving platforms) or alternate behaving solid such as o_solid_oneway
- Set the parent object of your Actors to o_actor (eg: players and enemies)
- The default collision event for Solids is no collision
- The default collision event for Actors is to set the move speed to zero
Input the desired move distance and collision event into the provided move functions. Note that Solids must be moved before Actors (eg: Solids are moved in the Begin Step event, Actors are moved in the Step event), however these functions can also be called from anywhere to move an object as a one-time event.
move_x(xspd, collision_event());
move_y(yspd, collision_event());
To use the default collision event of the parent, omit the collision_event parameter. The default event can be overridden by including a collision event script as seen above. The custom collision event passes the colliding Solid's instance ID as an argument. This can be used for triggering object specific reactions like determining surface-based particles and audio, and much much more.
//default collision event
move_x(xspd);
move_y(yspd);
//custom collision event
move_y(yspd, function(_inst)) {
collide_y();
show_debug_message("Vertical collision with: " + object_get_name(_inst.object_index));
});
Default movement variables are provided, however the default variables for handling fractional movement should not be changed:
//these can be changed
xspd = 0;
yspd = 0;
//do not change these!
xspd_remainder = 0;
yspd_remainder = 0;The o_actor parent includes a default Squash script in the event the Actor object is crushed between two Solid objects. The default event is empty and requires population or overriding within the child object. eg:
//in create event of player object (child of o_actor)
//override of parent squash function
function squash() {
instance_create_depth(x, y, -1, o_player_squash);
instance_destroy(id);
}
The function determining whether an Actor is riding a Solid should only be overriden or modified with care. This function helps Solids move an Actor when carrying them (as opposed to pushing them). For example, a wall clinging check was added for the player actor in the demo project, while the other checks help ensure the system works as intended and should not be changed:
function is_riding(_solid) {
//optional check for player wall clinging
if (clinging && cling_inst == _solid.id) { return true };
//actor is on top -- *do not modify*
if (place_meeting(x, y+1, _solid)) { return true };
//actor is underneath -- *do not modify*
if (place_meeting(x, y-1, _solid) && sign(_solid.yspd) == 1) { return true };
//actor is moving the same direction horizontally as a moving solid (moving faster than the solid) -- *do not modify*
return (place_meeting(x+sign(_solid.xspd), y, _solid) && sign(xspd) == sign(_solid.xspd));
}
Feel free to reach out to me on Discord if you have questions, comments, or are interested in contributing to the project: bennyfrancis#6146
- obj_frog (colmeye) for helping optimize and refactor the system and for answering all my questions
- The awesome people on the GameMaker Discord for all their help and support
- Pixel Frog who created the free Treasure Hunters asset pack available on itch.io
- Maddy Thorson who wrote the article on the Celeste and Towerfall move and collide system