Opacity Fade Question

candlelight

Hello.

I'm trying to figure out a way to properly fade out a Spine object in Unity. What I've been able to do so far is parent Spine prefabs to an empty container, and then do a foreach to change all the child-Spine opacities via the Skeleton Animation component. So, everything fades out at once, which is fine. Or I can fade out each one individually.

The problem, however, is that you can see the individual pieces of each Spine prefab since each slot is fading on its own. IE, a character with a body and 2 arms: when they all fade, you can see the 'hidden' pieces of the arm as it fades as they overlap with the body. Basically, it's not all fading in unison. Is there a way to properly fade a Spine character then?

One other question with that: is there a good way to opacity-fade between two Spine animations? Instead of one animation instantly jumping to the next one, I want to opacity-fade them into each other (one slowly fades away, the other slowly fades in). My idea right now involves layering two of the same prefab over each other and controlling opacities that way, but I was wondering if there's a more elegant/built-in solution. Thanks.

Pharan

This is two questions.

(1)
This is not particular to Spine. Any puppeted/skeletal 2D sprite system will fade out this way as long as it uses alpha blending.

This is a combination of reasons.
But 3D models can get around this because they have the ability to write to a depth buffer. While that causes artifacts of its own, at least its various parts don't overdraw and show overlaps.
This way of solving the problem is not available for assembled 2D sprites because it uses alpha blending around the edges, which means it can't properly write to the depth buffer. Normally, it doesn't ignore anything. It always just draws parts one after the other, which looks correct at full opacity but incorrect at anything less.

Game rendering always renders things piece by piece.
It doesn't pregroup/prerender them and change the opacity and re-composite that... the unless you tell it to. (which is some obscure programming I'm not too familiar with.)

Specifically for Unity, I've been wanting to look into having a Spine skeleton render to an FBO, rendering that to a quad and and fading that. I've had no luck so far even with a basic setup. Still mostly on the backburner. Been really busy these days.

(2)
No, there is no way to just fade between two Spine animations.
The two skeleton solution may be a good start but you'll still have the same problems as (1).

Right now, these fade effects may not be a good fit for 2D games.
I recommend you explore other ways to get around what you're trying to do.

Someone else who may have solved this could help though.

candlelight

Thank you for the reply. It helped me understand the problem better and what to properly search for (I had been doing "crossfade" searches that got me the wrong results). I finally understood that this is a shader problem for 2D sprites.

I did happen to find a shader that will allow composite Unity Sprite objects to blend together properly. Credit goes to the contributors of this thread: https://www.reddit.com/r/Unity2D/comments/3h7iha/shader_alpha_blending_help/

As long as the sorting orders of the composite Sprite parts in a proper order, it works great. I'm not yet knowledgeable enough about shader scripts to try anything with the Spine shader, but at least for the meantime I can use Unity's built-in sprite engine. I also included the script if anyone is interested.

2D_Alpha_Shader.zip

rxmarcus

Thanks for posting this shader script! I'm trying to use it but am having some strange visual artifacts. You said "As long as the sorting orders of the composite Sprite parts in a proper order, it works great.". Are you talking about the Draw Order of the different bones that gets set in the Spine editor? Can you help me understand in better detail what you had to do for this shader to work properly?

Thanks!

ramenero

Has anyone find a solution for this issue? I tried the shader posted above and it does not work properly.

We are currently using render texture on the spine object and displaying it in a quad and fading that.

but that punches FPS too much when going upwards of 3 objects.

has anyone else found a better solution?

this will severely hinder the usefulness of spine.

pag

My solution is to cover the transition with a special effect like a beam of light, particle explosion. Something appealing and juicy that fit with you game of course.