Oct
2
2012

Fake Godrays Shader

An article by mgear

Godrays shader on a plane texture.. since no RenderToTexturein indie. ( Converted to unity from this webgl shader)
Should try it as a camera shader also..

Features:
– Adjustable values: effect xy position, exposure, decay, density, weight, clamp, samples (screenshot is using 100 samples)

Webplayer:
http://unitycoder.com/upload/demos/fake_godrays_shader_unity/

Source (shader):

Shader "UnityCoder/Rays2"
{
    Properties 
    {
        tDiffuse ("Base (RGB)", 2D) = "white" {}
        fX ("fX", Float) = 0.5 // you can feed mouse xpos here with script: var mpos:Vector3 = Camera.main.ScreenToViewportPoint(Input.mousePosition); renderer.material.SetFloat( "fX", mpos.x);
        fY ("fY", Float) = 0.5 //  mouse ypos
        fExposure ("fExposure", Float) = 0.6
        fDecay ("fDecay", Float) = 0.93
        fDensity ("fDensity", Float) = 0.96
        fWeight ("fWeight", Float) = 0.4
        fClamp ("fClamp", Float) = 1.0
        //iSamples ("iSamples", Int) = 20
    }
    SubShader {
        Tags { "RenderType"="Opaque" }
        LOD 200
        Cull Off
         
        CGPROGRAM
        #pragma target 3.0
        #pragma surface surf Lambert
 
        sampler2D tDiffuse;
        float fX,fY,fExposure,fDecay,fDensity,fWeight,fClamp,iSamples;
 
        struct Input {
            float2 uvtDiffuse;
            float4 screenPos;
        };
 
        void surf (Input IN, inout SurfaceOutput o) 
        {
            int iSamples=100;
            float2 vUv = IN.uvtDiffuse;
            //vUv *= float2(1,1); // repeat?
            float2 deltaTextCoord = float2(vUv - float2(fX,fY));
            deltaTextCoord *= 1.0 /  float(iSamples) * fDensity;
            float2 coord = vUv;
            float illuminationDecay = 1.0;
            float4 FragColor = float4(0.0);
            for(int i=0; i < iSamples ; i++)
            {
                coord -= deltaTextCoord;
                float4 texel = tex2D(tDiffuse, coord);
                texel *= illuminationDecay * fWeight;
                FragColor += texel;
                illuminationDecay *= fDecay;
            }
            FragColor *= fExposure;
            FragColor = clamp(FragColor, 0.0, fClamp);
            float4 c = FragColor;
            o.Albedo = c.rgb;
            o.Alpha = c.a;
             
        }
        ENDCG
    } 
    FallBack "Diffuse"
}

—

Image#2: Texture used for the plane, you can use any texture..

Tags: god rays, godrays, light, ray, shader, shining

About the Author:

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11 Comments + Add Comment

Johan 31/10/2012 at 07:20

Seems buggy.

Reply
- mgear 31/10/2012 at 09:38
  
  Which part?
  
  Reply
Warren McCoy 31/01/2013 at 17:01

Does not run in 3.5.6f4 Engine/Webplayer setup, get corrupted error

Reply
- mgear 31/01/2013 at 17:04
  
  I’ll check on what version it was build.. (atleast with latest 4.x webplayer it works)
  
  Reply
- mgear 31/01/2013 at 22:36
  
  Maybe you can report a bug to unity..(or if anyone else can confirm that its working or not?)
  
  Reply
GuySl 12/05/2013 at 22:45

Is it working on Android and iOS?

Reply
- mgear 12/05/2013 at 22:53
  
  Not tested.. i’ll try to test it over next week.
  
  Reply
GuySl 21/05/2013 at 22:23

Any news regarding Android/iOS?

Reply
- mgear 21/05/2013 at 23:46
  
  Sorry forgot to test ipad, but on old galaxy s android it was too slow ~5fps
  (with 40 samples..webplayer had 100samples i think, and with much less samples (like 16..32..) it starts to look bad)
  
  So no use in mobiles.
  
  Reply
sajeel 22/08/2018 at 05:59

Hi,
I am trying to do something similar but the shader does not work with unity 2018.2 says compile error

Shader error in ‘UnityCoder/Rays2’: incorrect number of arguments to numeric-type constructor at line 41 (on d3d11)

What i want is like rays coming out of a perticular point (alpha image soft of rays for hologram’s light emmision point in the shape of hologram) please help if you can Thank you in advance

Reply
- mgear 22/08/2018 at 13:45
  
  for the error, try:
  float4 FragColor = float4(0,0,0,0);
  
  Reply