Mar
23
2016

Volumetric Image Effect Shader

An article by mgear

volumetric_effect_unity_1

Converted this old godrays shader ( http://unitycoder.com/blog/2012/10/02/fake-godrays-shader/ ) into image effect – interesting results! (see video below)

Source codes below (Attach script to main camera)

	using UnityEngine;

	[ExecuteInEditMode]
	public class VolumetricImageEffect : MonoBehaviour
	{
	public float exposure=0.6f;
	public float decay = 0.95f;
	public float density = 0.96f;
	public float weight = 0.4f;
	public float clamp = 1f;
	public int samples = 16;

	private Material material;

	// Creates a private material used to the effect
	void Awake()
	{
	material = new Material(Shader.Find("Hidden/VolumetricLightApproximation"));
	}

	// Postprocess the image
	void OnRenderImage(RenderTexture source, RenderTexture destination)
	{
	if (material == null)
	{
	material = new Material(Shader.Find("Hidden/VolumetricLightApproximation"));
	}

	material.SetFloat("fExposure", exposure);
	material.SetFloat("fDecay", density);
	material.SetFloat("fDensity", density);
	material.SetFloat("fWeight", weight);
	material.SetFloat("fClamp", clamp);
	material.SetInt("fSamples", samples);

	Graphics.Blit(source, destination, material);
	}
	}

view raw

VolumetricImageEffect.cs

hosted with ❤ by GitHub

	// original source: http://demo.bkcore.com/threejs/webgl_tron_godrays.html
	// converted to surface shader : http://unitycoder.com/blog/2012/10/02/fake-godrays-shader/
	// converted to image effect :

	Shader "Hidden/VolumetricLightApproximation"
	{
	Properties
	{
	_MainTex ("Texture", 2D) = "white" {
	}

	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
	fSamples ("fSamples", Int) = 32


	}
	SubShader
	{
	// No culling or depth
	Cull Off ZWrite Off ZTest Always

	Blend SrcAlpha OneMinusSrcAlpha // Traditional transparency

	Pass
	{
	CGPROGRAM
	#pragma vertex vert
	#pragma fragment frag

	#include "UnityCG.cginc"

	struct appdata
	{
	float4 vertex : POSITION;
	float2 uv : TEXCOORD0;
	};

	struct v2f
	{
	float2 uv : TEXCOORD0;
	float4 vertex : SV_POSITION;
	};

	v2f vert (appdata v)
	{
	v2f o;
	o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
	o.uv = v.uv;
	return o;
	}

	sampler2D _MainTex;
	float fX,fY,fExposure,fDecay,fDensity,fWeight,fClamp;
	int fSamples;


	fixed4 frag (v2f i) : SV_Target
	{
	float2 vUv = i.uv;
	float2 deltaTextCoord = float2(vUv – float2(0.5,0.5));
	deltaTextCoord = 1.0 / float(fSamples) fDensity;
	float2 coord = vUv;

	float illuminationDecay = 1.0;
	float4 FragColor = float4(0,0,0,0);

	for(int i=0; i < fSamples ; i++)
	{
	coord -= deltaTextCoord;
	float4 texel = tex2D(_MainTex, coord);
	texel = illuminationDecay fWeight;
	FragColor += texel;
	illuminationDecay *= fDecay;
	}

	FragColor *= fExposure;
	FragColor = clamp(FragColor, 0.0, fClamp);
	float4 c = FragColor;

	return c;
	}

	ENDCG
	}
	}
	}