Following on from what was said, texture backdrop is a good function for the purpose. Note that this textures the background of the current camera.
You should be fine with texture backdrop; but there are more CPU friendly ways to draw an image on the screen; just choose what is most convenient for you and your players.
If accuracy of screen co-ordinates is not important; you can quickly and easily take advantage of the accelerated Graphics Processing Unit to draw an image as a texture on a 3D plane, facing the camera using
do
distance# = 100.0
position object id, camera x(), camera y(), camera z()
set object to camera orientation id
move object id, -distance#
point object id, camera x(), camera y(), camera z()
loop
or similar.
We are practically drawing 2 polygons and an image using the GPU, without having to calculate the screen co-ordinates; although you may choose to delve into [pick screen] commands and
rotation calculations if you feel it is necessary. You don't even have to use as much as 2 polygons forming a plane, a single polygon can do the job with some maths.
Whether a 2D game or 3D game, a background is a background; your players do not care what goes in, they care about what they get out of it; therefore, nobody says you have to always use 2D commands for 2D games, don't be afraid to use the 3D commands as well.
For example drawing a shaded 3D sphere with an
.FX shader is easier for your computer to do than drawing a filled 2D circle using dot commands. The industry is building the hardware to make use of that Z axis.
Note that there are
faster 2D command functions available.
It sounds like overkill but the advantage is quite simply, render speed. It allows you to draw one, two even ten images on the screen without losing much performance; 20, 30, 50 images if you like, all the computer has to do is shade some polygons! How many millions of polygons does your graphics card support? -All this whilst also being able to use Texture Backdrop at the same time.
Compared to pasting sprites and images which slows down your CPU dramatically even for one image, and also Texture Backdrop, which only supports one image; this method is useful for special effects in the background, foreground, characters, entities, anywhere you like. You do not even have to use sprites for characters if you don't want to! You could ignore the Z axis and work with X and Y positions with 3D planes which support FX shaders and all of the 3D object commands. Furthermore, who says you have to use images instead of models or particles?
It is all up to you.
Finally, for advanced situations in the future, [texture screen] will give you FULL control over the screen; therefore when you get more experienced, you can control the GPU rendering process; draw your scene exactly how you want it, with backgrounds, movies, FX, dark, bright, blue, pink whatever.
