Flashing/ Blinking MeshRenderer

danthat

Hello! I'm trying to make my Spine guys flash white when hit, in that classic game style. I'm using Unity, and swapping shaders over several times a second is going to be very slow.

Just wondering if there's something clever I can do at Spine's end? The SkeletonLit shader doesn't allow for colour changes, and I'm grasping at straws as to how to do the effect cleanly.

Any advice would be much appreciated. I'm sort of hoping there's a magic setting on Spine I haven't noticed 🙁

danthat

Nate

Pharan mentioned something here:
viewtopic.php?p=12434#p12434

I'd be modding it either way to darken the vertex colors it pushes 'cause we're using a modified version of the Skeleton shader that allows it to overbrighten the texture way past RGBA(1,1,1,1)— because flashing skeletons make good game feedback!

Maybe he can share what he uses.

You could use an IF in a shader:

Shader "Spine/Skeleton Flash" {
   Properties {
      _Cutoff ("Shadow alpha cutoff", Range(0,1)) = 0.1
      _MainTex ("Texture to blend", 2D) = "black" {}
      _Flash ("Flash", Range(0,1)) = 0
      _FlashColor ("Flash color", Color) = (1,1,1,1)
   }
   SubShader {
      Cull Off
      ZWrite Off
      Blend One OneMinusSrcAlpha
      Lighting Off

  Pass {
     CGPROGRAM
     #pragma vertex vert_img
     #pragma fragment frag

     #include "UnityCG.cginc"

     uniform sampler2D _MainTex;
     uniform float _Flash;
     uniform float4 _FlashColor;

     float4 frag(v2f_img i) : COLOR {
        float4 t = tex2D(_MainTex, i.uv);
        if (_Flash != 0) {
           t.r = t.a;
           t.g = t.a;
           t.b = t.a;
           t = t * _FlashColor;
        }
        return t;
     }
     ENDCG
  }
   }
}

Branching in a shader isn't recommended, but I doubt will be a problem. I don't know how compatible this shader is for every kind of device though.

danthat

Thanks Nate!

The only other solution I found was to push the skeleton's rgb values off the scale; setting each to 1000 bleaches the mesh out, but causes some transparency issues where the images overlap. Looks cool, but won't work everywhere.

Alternative is to set rgb to 0,0,0, and have them flash black. Which also looks pretty neat.

Søren

Could the character for a single frame be rendered to FBO and then use the alpha as a mask for a white overlay maybe?
Not sure how efficient it would be or even if it's possible I'm just thinking how I would do it if I had to do it for something pre-rendered (which is what I used to work with)

Pharan

My solution was to modify the shader to overbrighten via vertex colors. Pretty standard stuff (at least as far as I've seen some Unity shaders).

It's a two part solution:
Imagine an maximum-overbrightening value: like 4.

(1) Change the shader to multiply the texture contribution * vertex color contribution * 4
(in ShaderLab, this is something texture * primary QUAD, texture * primary. The second formula defines the treatment of the alpha channel )

(2) Change SkeletonRenderer to push vertex color values that are multiplied by 1/4.
this amounts to adding an extra factor to the color calculation in SkeletonRenderer when it sets rgba before the vertices get assigned to the mesh.

The result is that if you set Skeleton.r g or b to 1, it'll be normally colored, as this pushes a maximum of 0.25 to the vertices.
But you can set Skeleton.r g or b up to 4, and it'll overbrighten the thing. This'll push 1's to the vertices which get calculated into * 4 by the shader. This was kind of a workaround thing because you can't assign vertex colors with element values larger than 1.0 (or larger than 255?)

It's important in these modifications that the alpha channel remain untouched on both ends or the edges will get messed up. no extra multiplication on them.

I brought this up last year, Nate! XD

Anyway, just a note, doing it in ShaderLab seems to cause it to not function correctly on some fairly recent (2-3-year-old) Android devices.
I would think coding it in Cg would fix it. If only I knew enough about Cg.

Also, this is purely an overbrightening shader so black texture pixels will always be black, and near-black pixels don't brighten very well.
But it won't break batching... but I guess that' not much of a benefit.