Unity | Swirl Shader

swirl.shader

// Ref: http://www.geeks3d.com/20110428/shader-library-swirl-post-processing-filter-in-glsl/
// Swirl Effect for Unity

Shader "Custom/swirl" {
	Properties {
		_Color ("Color", Color) = (1,1,1,1)
		_MainTex ("Albedo (RGB)", 2D) = "white" {}
		_Glossiness ("Smoothness", Range(0,1)) = 0.5
		_Metallic ("Metallic", Range(0,1)) = 0.0
	}
	SubShader {
		Tags { "RenderType"="Opaque" }
		LOD 200
		
		CGPROGRAM
		// Physically based Standard lighting model, and enable shadows on all light types
		#pragma surface surf Standard fullforwardshadows

		// Use shader model 3.0 target, to get nicer looking lighting
		#pragma target 3.0

		sampler2D _MainTex;

		struct Input {
			float2 uv_MainTex;
		};

		half _Glossiness;
		half _Metallic;
		fixed4 _Color;

		// Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
		// See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
		// #pragma instancing_options assumeuniformscaling
		UNITY_INSTANCING_CBUFFER_START(Props)
			// put more per-instance properties here
		UNITY_INSTANCING_CBUFFER_END
		
		// possibly add interactivity
		//uniform float radius
		//uniform float angle
		//uniform float2 center

		fixed4 Swirl(sampler2D tex, inout float2 uv, float time) {
			float radius = _ScreenParams.x;
			float2 center = float2(_ScreenParams.x, _ScreenParams.y);
			float2 texSize = float2(_ScreenParams.x / 0.5, _ScreenParams.y / 0.5);
			float2 tc = uv * texSize;
			tc -= center;
			float dist = length(tc);
			float angle = sin(_Time.y * 0.15);
			if (dist < radius)
			{
				float percent = (radius - dist) / radius;
				float theta = percent * percent * angle * 28.0;
				float s = sin(theta);
				float c = cos(theta);
				tc = float2(dot(tc, float2(c, -s)), dot(tc, float2(s, c)));
			}
			tc += center;
			float3 color = tex2D(tex, tc / texSize).rgb;
			//color.r = 1.0;
			return fixed4(color, 1.0);
		}

		void surf (Input IN, inout SurfaceOutputStandard o) {
			// Albedo comes from a texture tinted by color
			//fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
			fixed4 c = Swirl(_MainTex, IN.uv_MainTex.xy, 1) * _Color;
			o.Albedo = c.rgb;
			// Metallic and smoothness come from slider variables
			o.Metallic = _Metallic;
			o.Smoothness = _Glossiness;
			o.Alpha = c.a;
		}
		ENDCG
	}
	FallBack "Diffuse"
}

/*
vec4 PostFX(sampler2D tex, vec2 uv, float time)
{
	vec2 texSize = vec2(rt_w, rt_h);
	vec2 tc = uv * texSize;
	tc -= center;
	float dist = length(tc);
	if (dist < radius)
	{
		float percent = (radius - dist) / radius;
		float theta = percent * percent * angle * 8.0;
		float s = sin(theta);
		float c = cos(theta);
		tc = vec2(dot(tc, vec2(c, -s)), dot(tc, vec2(s, c)));
	}
	tc += center;
	vec3 color = texture2D(tex0, tc / texSize).rgb;
	return vec4(color, 1.0);
}
*/