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