Fade Material's Transparency Based on Distance

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Okay, so I've been at this for hours now and still no luck. Thought I'd see if the pros here could help me out :)

So I have everything working correctly except it's opposite:

 dist = Vector3.Distance(transform.position, other.position);
     renderer.material.color.a = dist * .02;

It fades the material when I get closer and then unfades it as I get further away (opposite effect).

How can I fix this? I tried using -Vectot3.Distance and I get some crazy distance number. This is tough because Unity is limited with their scripting references and all they have is Vector3.Distance. Is there another way I can do this? Any help or guidance would be much appreciated and I'll be sure to give an answered question if you can help me get this working. Thanks

Answer 1

Best Answer

Answer by aldonaletto · Apr 20, 2012 at 12:52 AM

Alpha = 0 means transparent, while alpha = 1 means solid. You could use something like this:

var solidDistance: float = 5.0; // max distance to be 100% solid
...
dist = Vector3.Distance(transform.position, other.position);
if (dist < solidDistance) dist = solidDistance;
renderer.material.color.a = solidDistance / dist;

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BHS · Apr 20, 2012 at 01:14 AM 0

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Thank you for this! added a couple things to it to make it faded more gradual and it's almost perfect. How can I fade multiple materials if an object has more than one? So do the same but for all the materials on the object that the script is on?

aldonaletto · Apr 20, 2012 at 01:21 AM 0

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I think you must do the same thing for each material - and the materials must have transparent shaders as well, or the alpha will do nothing.

BHS · Apr 20, 2012 at 01:33 AM 0

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Ok, thank you. Last question, I know how you have to have a transparent material, but is it possible to have one that is able to cast and receive shadows, such as transparent bumped specular? Or am I gonna have to rewrite the shader..

BHS · Apr 20, 2012 at 02:29 AM 0

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Would I be able to use an array to control all the materials at once, then assign the materials that will be used.

var fadeMaterial : Material[];

renderer.material = fadeMaterial[0];

renderer.material.color.a = solidDistance / dist * 10;

How can I control an array of materials? Or is this not possible?

aldonaletto · Apr 20, 2012 at 10:55 AM 0

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I don't know much about shadows, but suspect that they have nothing to do with the shader itself - it seems that they are generated in another process, and only some material properties are taken into account (but I'm not 100% sure about this).
According to the docs, when you modify any renderer.material characteristic, a local copy is created in order to not modify other objects that use the same material. I think that if you have an array of renderers and modify their materials, other objects will not be affected - but if it's an array of materials, you may modify all objects that use them.

Answer 2

Answer by wolvtodd · Apr 20, 2012 at 01:13 AM

I think renderer.material.color can only return a new color, and can not just set a new single alpha value. how about trying this:

renderer.material.color = new Color(renderer.material.color.r, renderer.material.color.g, renderer.material.color.b, solidDistance / dist);

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BHS · Apr 20, 2012 at 01:22 AM 0

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No it works, I have used the same thing in different codes. What it does is just control the alpha value and nothing else.

Answer 3

Answer by Seyed_Morteza_Kamaly · Jan 20, 2018 at 03:52 PM

create shader and copy and paste then add this to your object

 Shader "Kamaly/FarAlpha"
 {
     Properties
     {
         _MainTex ("Texture", 2D) = "white" {}
         _MinVisDistance("MinDistance",Float) = 0
         _MaxVisDistance("MaxDistance",Float) = 20
             _Color("Color",Color) = (0,0,0,1)
     }
     SubShader
     {
             ZWrite Off
             Blend SrcAlpha OneMinusSrcAlpha
         Tags { "RenderType"="Transparent" }
         LOD 100
 
         Pass
         {
             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag 
             // make fog work
             #pragma multi_compile_fog
             
             #include "UnityCG.cginc"
 
         struct v2f
     {
         half4 pos       : POSITION;
         fixed4 color : COLOR0;
         half2 uv        : TEXCOORD0;
     };
 
 
 
     sampler2D   _MainTex;
     half        _MinVisDistance;
     half        _MaxVisDistance;
 
 
 
     v2f vert(appdata_full v)
     {
         v2f o;
 
         o.pos = mul((half4x4)UNITY_MATRIX_MVP, v.vertex);
         o.uv = v.texcoord.xy;
         o.color = v.color;
 
         half3 viewDirW = _WorldSpaceCameraPos - mul((half4x4)unity_ObjectToWorld, v.vertex);
         half viewDist = length(viewDirW);
         half falloff = saturate((viewDist - _MinVisDistance) / (_MaxVisDistance - _MinVisDistance));
         o.color.a *= (1.0f - falloff);
         return o;
     }
 
 
     fixed4 frag(v2f i) : COLOR
     {
         fixed4 color = tex2D(_MainTex, i.uv) * i.color;
     return color;
     }
             ENDCG
         }
     }
 }

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j4p20r · Oct 22 at 09:01 AM 0

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@Seyed_Morteza_Kamaly I like your shader, thanks for sharing!

I've made two small adjustments, that you might like. First of all I added "queue=transparant" to the tags, so that it is drawn later than solid geometry (sometimes your shader pops behind a solid object).

Furthermore I also moved the code for calculating the alpha to the frag method, this causes the alpha to be determined on pixel level, instead of vertex level. For instance a long cube, would be invisible at it's center, because there's no vertices there.

Again thanks for sharing this helped me out with some problems I had myself ;). Here's my version:

 Shader "Kamaly/FarAlpha"
 {
     Properties
     {
         _MainTex ("Texture", 2D) = "white" {}
         _MinVisDistance("MinDistance",Float) = 0
         _MaxVisDistance("MaxDistance",Float) = 20
         _Color("Color",Color) = (0,0,0,1)
     }
     SubShader
     {
         ZWrite Off
         Blend SrcAlpha OneMinusSrcAlpha
         Tags { "RenderType"="Transparent" "Queue"="Transparent" }
         LOD 100
         
         Pass
         {
             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag 
             // make fog work
             #pragma multi_compile_fog
             
             #include "UnityCG.cginc"
  
             struct v2f
             {
                 half4 pos        : POSITION;
                 fixed4 color    : COLOR0;
                 half2 uv        : TEXCOORD0;
                 half4 vert        : TEXCOORD1;
             };
 
             sampler2D   _MainTex;
             half        _MinVisDistance;
             half        _MaxVisDistance;
             fixed4      _Color;
  
  
  
             v2f vert(appdata_full v)
             {
                 v2f o;
                 
                 o.pos = mul((half4x4)UNITY_MATRIX_MVP, v.vertex);
                 o.vert = v.vertex;
                 o.uv = v.texcoord.xy;
                 o.color = _Color;
                 return o;
             }
  
  
             fixed4 frag(v2f i) : COLOR
             {
                 half3 viewDirW = _WorldSpaceCameraPos - mul((half4x4)unity_ObjectToWorld, i.vert);
                 half viewDist = length(viewDirW);
                 half falloff = saturate((viewDist - _MinVisDistance) / (_MaxVisDistance - _MinVisDistance));
                 i.color.a *= (1.0f - falloff);
 
                 fixed4 color = tex2D(_MainTex, i.uv) * i.color;
                 return color;
             }
             ENDCG
          }
      }
  }

Fade Material's Transparency Based on Distance

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