gml_starfield_generator

A script to generate starfields in GameMaker’s GML language.

Overview

Since I found drawing starfields in Photoshop and importing them into GM a waste of texture-page space, I created this little script that creates starfields from scratch onto a transparent surface which can be drawn onto any background. The script is highly customizable and extensively commented so it should be fairly easy to use and modify.

Usage

1. Download the two provided GML files

2. Import the two files as scripts into your Game Maker project

3. Create a new object

4. Add a Creation event and type the following in it:

    madestars = false;
    starsprite = undefined;
    surf_starfield = -1; //do not use anything but -1 for surface variables
   

5. Add a Draw event then type the folling:

    if (madestars == false) {
    //make the star surface
    if(surf_starfield == -1){
            surf_starfield = scr_fx_starfield_init(surf_starfield)
    }
    starsprite = sprite_create_from_surface(surf_starfield, 0,0, room_width,room_height, false, false, 0,0);
    surface_free(surf_starfield);
    madestars = true;
    }
   
    gpu_set_blendmode(bm_add);
    draw_sprite(starsprite, 0, 0, 0);
    gpu_set_blendmode(bm_normal);
   

6. In the Destory event add this:

    if (sprite_exists(starsprite)) {
    sprite_delete(starsprite);
    }
   

7. Modify the values in scr_fx_starfield_init to your needs.

To create a new starfield, just create an instance of the object at any coordinates.

Notes

Since the starfield is drawn onto a surface that is inherently volatile, it’s good practice to check whether it still exists and re-draw it, if necessary. Surfaces get destroyed when switching to/from full screen, for example.