GameMaker how to do stuff every time an animation updates

[Capptianm]

I thought that the Animation_Update event to do just what it said on the box. I thought this event would activate every time an objects image index changes. It turns out that this event is only meant for skeletal animation. is there any way to activate some code when the image index updates?

 

[FrostyCat]

Create:

image_index_previous = image_index;

End Step:

if (image_index_previous != image_index) {
  /* Perform actions here */
  image_index_previous = image_index;
}

 

[Capptianm]

this

Create:

image_index_previous = image_index;

End Step:

if (image_index_previous != image_index) {
  /* Perform actions here */
  image_index_previous = image_index;
}

this doesn't exactly work, it constantly activates the code. since the code plays an audio file, it plays that audio file every second. any other options?

 

[MeBoingus]

The way that code works is:

Every time the frame (image_index) changes - the code is triggered.

Could you better describe what you expected/need to happen?

 

[NeZvers]

I think I know what's the problem.
image_index updates by image_speed each frame and so @FrostyCat suggested code will fire each frame. So if you need on each sprite image_index change do this:

if (image_index_previous != floor(image_index)) {
  /* Perform actions here */
  image_index_previous =floor(image_index);
}

 

[MeBoingus]

I think I know what's the problem.
image_index updates by image_speed each frame and so @FrostyCat suggested code will fire each frame. So if you need on each sprite image_index change do this:

if (image_index_previous != floor(image_index)) {
  /* Perform actions here */
  image_index_previous =floor(image_index);
}

This would indeed do the trick. If you DO need to do anything with the areas 'between' frames, here's some info:

Frames are actually decimals.

Let's say we have a sprite with 4 frames.
If your image speed is 1.5, and you're on frame 0, this is what happens:

Image index 1.4 is considered (by the engine) to be image index 1. It will show the first frame.
However, image index 1.5 is rounded up to 2, and will thus show the 2nd frame.

The reason using 'floor' works here, is it rounds the numbers down, so that we're not working with decimals.
Otherwise that code would trigger every frame (1, 1.1, 1.2, etc).

That code above will only trigger whenever the frame changes by a whole number (1, 2, 3, etc).

 

[NeZvers]

This would indeed do the trick. If you DO need to do anything with the areas 'between' frames, here's some info:

Frames are actually decimals.

Let's say we have a sprite with 4 frames.
If your image speed is 1.5, and you're on frame 0, this is what happens:

Image index 1.4 is considered (by the engine) to be image index 1. It will show the first frame.
However, image index 1.5 is rounded up to 2, and will thus show the 2nd frame.

The reason using 'floor' works here, is it rounds the numbers down, so that we're not working with decimals.
Otherwise that code would trigger every frame (1, 1.1, 1.2, etc).

That code above will only trigger whenever the frame changes by a whole number (1, 2, 3, etc).

I don't think there's rounding to native image_index but floor rounding, hence I suggested to use it.
If there's 0.5 rounding up, then it means 0th image_index will be shown for half supposed length and last one 1.5x it's supposed length.