Question: How does the Z axis work in GameMaker?

Answer

GameMaker Studio traditionally operates on a 2D plane, using the X and Y axes for positioning objects within a room. While there is no explicit Z axis as you would find in 3D game development environments, GameMaker can simulate a Z axis to create the illusion of depth or to layer objects.

To manage depth (which can be thought of as a pseudo-Z axis), you typically manipulate the depth property of instances. The lower the depth value, the closer the object appears to the foreground, whereas higher values move the object towards the background.

Here's an example of setting an object's depth dynamically:

// Assuming 'y' is our pseudo-Z axis, we could make objects higher up on the screen draw beneath those lower down.
instance_create_layer(x, y, "Instances", obj_Enemy).depth = -y;

In the above code, objects with a higher Y coordinate (further down the screen) will be drawn on top of objects with a lower Y coordinate (further up the screen), creating a simple top-down depth effect.

For more complex effects that require a sense of the third dimension, such as isometric games, developers often use a combination of depth sorting and sprite angles/scales to simulate a 3D environment. Additionally, GameMaker offers functionality for working with layers and cameras that can further enhance the feeling of depth.

Starting from GameMaker Studio 2.3 and onwards, developers also have access to layer functions which can be used to control the drawing order of instances and tiles, effectively manipulating the Z order of elements in the scene.

Here’s how you might use layers to control depth:

// Create a new layer above the current one and set its depth
var new_layer = layer_create(layer_get_depth("current_layer")-100);
layer_add_instance(new_layer, instance_id);

While these methods don't offer true 3D space manipulation, they do allow for a great deal of control over the rendering order and appearance of objects, offering a way to simulate a Z axis in GameMaker's predominantly 2D environment.