Unity Burn Shader for mobile question.

Hello , struggling for some time with moving this shader

Code (CSharp):

1. Shader "Custom/DissolveWithBurns" {
2.      Properties {
3.         _MainTex ("Texture (RGB)", 2D) = "white" {}
4.         _SliceGuide ("Slice Guide (RGB)", 2D) = "white" {}
5.         _SliceAmount ("Slice Amount", Range(0.0, 1.0)) = 0.5
6.  
7.         _BurnSize("Burn Size", Range(0.0, 1.0)) = 0.15
8.         _BurnRamp("Burn Ramp (RGB)", 2D) = "white" {}
9.     }
10.     SubShader {
11.       Tags { "RenderType" = "Opaque" }
12.       Cull Off
13.       CGPROGRAM
14.      
15.       #pragma surface surf Lambert
16.       struct Input {
17.           float2 uv_MainTex;
18.           float2 uv_SliceGuide;
19.           float _SliceAmount;
20.       };
21.  
22.       sampler2D _MainTex;
23.       sampler2D _SliceGuide;
24.       float _SliceAmount;
25.       sampler2D _BurnRamp;
26.       float _BurnSize;
27.  
28.    
29.       void surf(Input IN, inout SurfaceOutput o) {
30.  
31.           clip(tex2D(_SliceGuide, IN.uv_SliceGuide).rgb - _SliceAmount);
32.           o.Albedo = tex2D(_MainTex, IN.uv_MainTex).rgb;
33.  
34.           half test = tex2D(_SliceGuide, IN.uv_MainTex).rgb - _SliceAmount;
35.  
36.  
37.           if (test < _BurnSize) {
38.           o.Emission = tex2D(_BurnRamp, float2(test *(1 / _BurnSize), 0));
39.           o.Albedo *= o.Emission;
40.           }
41.       }
42.  
43.       ENDCG
44.     }
45.     Fallback "Diffuse"
46. }
47.  

(direct copy-paste from http://www.codeavarice.com/dev-blog/tutorial-burning-edges-dissolve-shader-in-unity)

for mobile.

And it fails.
And I can't understand 2 thins :
1.
half test = tex2D(_SliceGuide, IN.uv_MainTex).rgb - _SliceAmount;
scalar = 3dimenstionVector - scalar.
I get the extraction part, but assigning vector to scalar blows my mind.

2. Have no idea why it fails to run on mobile.

Any help? Pls)

 

Does it work on the editor and fail on mobile?

(and yeah, that casting from 3channels to a scalar is not something that should be done, it might as well be why it doesn't work on mobile, depending on the platform, casting like that may or may not work. Maybe change it so that it reads only one channel?)

 

Editor and windows looks and behaves just as planned.
I've done some code juggling, "removing if", partial code disabling, but failed to extract the problem part.

half test = tex2D(_SliceGuide, IN.uv_MainTex).r - _SliceAmount;

Reducing rgb=>to r , didn't help(

 

Is it pink on mobile, or does it simply do something different?

What happens if you remove the clip line?

 

Not pink, shader compiles without errors.

looks like this part is ignored.

Code (CSharp):

1. if (test < _BurnSize) {
2.           o.Emission = tex2D(_BurnRamp, float2(test *(1 / _BurnSize), 0));
3.           o.Albedo *= o.Emission;
4.           }

It shoud change color on the border of clipping.

 

Code (CSharp):

1. clip(tex2D(_SliceGuide, IN.uv_SliceGuide).rgb - _SliceAmount);
2.        
3.  
4.         half test = tex2D(_SliceGuide, IN.uv_MainTex).rgb - _SliceAmount;
5.    
6.         o.Albedo = float3(0.0, 0.0, 1.0);
7.    
8.  
9.  
10.        
11.         o.Albedo =  float3(1.0, 0.0, 0.0)* step(test, _BurnSize) +
12.                     float3(0.0, 1.0, 0.0)* (1-step(test, _BurnSize));

even simplified logic to this still gets constant color on mobile.
In opposite to desktop "burned" effect.

 

Try writing to Emission instead of Albedo.

 

Nope, didn't help either. It feels like shader picks one of 2 colors and sticks to them cutting out everything else.

 

The step() function makes the code shorter, but doesn't actually reduce the complexity of the shader.

The following two lines will result in identical compiled shaders.
float val = step(y, x);
float val = (x >= y) ? 1 : 0;

However some android devices are totally broken when doing comparisons like that, it's entirely plausible your specific device isn't showing correctly but others would.

My suggestion is to do the compare with out using a comparison, like:

float burn = saturate((test - _BurnSize) * 1000.0);
o.Albedo = lerp(float3(1.0, 0.0, 0.0), float3(0.0, 1.0, 0.0), burn);

 

Wow! Thanks! It's sort of working) Got a little polish to do, but that I can handle)