Transparrent Highlight shader

Unity Engine
1

It’s a little bit tricky to explain what I want to do, but hopefully the images will help clarifying it.

I want to make a shader that takes two textures. The first texture should highlight the texture beneath it, using additive blending.

Texture 1: Black and white image used for Highlight.
Texture 2: RGBA image, alpha is telling what part to render.
Animated UV script is added to scroll the highlight image across the mesh.

So far (with help from a friend) I get this result:
The text alpha is correct and overlay is displaying sort of correct but the text is black.

1499330--84250--$highlightshader2.jpg
1499330--84250--$highlightshader2.jpg977×775 141 KB

This is the additive effect I want but it should only display within the alpha (which is the text border).

1499330--84248--$highlightshader.jpg
1499330--84248--$highlightshader.jpg977×775 104 KB

Here is the code so far (at the moment it displays the text correct but not the highlight, I can sort of see the highlight moving beneath the text when I animate the UV’s):

Here are the texture files: http://www.coindrop.dk/unityforum/highlightshadertextures.zip

Hope someone can point me in the right direction. :sunglasses:

Shader "Decal2" {
Properties {
	_Color ("Main Color", Color) = (1,1,1,1)
	_MainTex ("Base (RGB)", 2D) = "white" {}
	_DecalTex ("Base (RGB) Trans (A)", 2D) = "white" {}
}

SubShader {
	//Tags { "RenderType"="Opaque" }
	//Tags {"Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent"}
	//LOD 200

	
	
CGPROGRAM
#pragma surface surf Lambert alpha

sampler2D _MainTex;
sampler2D _DecalTex;
fixed4 _Color;

struct Input {
	float2 uv_MainTex;
	float2 uv_DecalTex;
};

void surf (Input IN, inout SurfaceOutput o) {
	fixed4 c = tex2D(_MainTex, IN.uv_MainTex);
	half4 decal = tex2D(_DecalTex, IN.uv_DecalTex);
	
 c.rgb = lerp (c.rgb, decal.rgb, decal.a);
 //c.rgb = lerp (decal.rgb, c.rgb, decal.a);
 c.a *= decal.a; 
 c *= _Color;
 o.Albedo = c.rgb;
 o.Alpha = c.a;
	
}
ENDCG




}

Fallback "Diffuse"
}
2

You may try to replace line 31 with:

c.rgb = c.rgb + decal.rgb;
3

You Sir, have just ended a very long struggle for me to figure out this shader - Thank you so much!
As an artist is’t not always easy to figure this stuff out… Think i am getting better at it though :slight_smile:

For anyone who may wish to try out this shader, here are the texture files and the final code (you also need to animate the UV’s with a script):

Textures: http://www.coindrop.dk/unityforum/highlightshadertextures.zip

Shader "Decal2" {

Properties {

    _Color ("Main Color", Color) = (1,1,1,1)

    _MainTex ("Base (RGB)", 2D) = "white" {}

    _DecalTex ("Base (RGB) Trans (A)", 2D) = "white" {}

}

 
SubShader {


CGPROGRAM

#pragma surface surf Lambert alpha

 
sampler2D _MainTex;

sampler2D _DecalTex;

fixed4 _Color;
 

struct Input {

    float2 uv_MainTex;

    float2 uv_DecalTex;

};

 
void surf (Input IN, inout SurfaceOutput o) {

    fixed4 c = tex2D(_MainTex, IN.uv_MainTex);

    half4 decal = tex2D(_DecalTex, IN.uv_DecalTex);

    
c.rgb = c.rgb + decal.rgb;

 c.a *= decal.a; 

 c *= _Color;

 o.Albedo = c.rgb;

 o.Alpha = c.a;

    

}

ENDCG

 
}

 
Fallback "Diffuse"

}
4

I’m assuming your problem was due to the lerp function meaning that either the decal was showing through fully with the decal.a being 1:

c.rgb = lerp (c.rgb, decal.rgb, 1) = full decal texture.

When the decal was transparent (alpha 0):

c.rgb = lerp (c.rgb, decal.rgb, 0) = full normal texture (Except these areas are transparent)

Hence why if you reversed the lerp function:

c.rgb = lerp (decal.rgb, c.rgb, 1) = full normal texture (Black text)

you ended up using the main texture on the text, causing it to be black.

5

Yeah, I think that was the case. Thank you for the explanation :slight_smile: