Shader Story

Patterns & Shapes: Whirl

This pattern uses polar coordinates, angle, and radius combined with frac() and step() to create a swirling, tileable whirl effect. Great for dynamic backgrounds, stylized distortions, or rotational transitions.

half2 uvs_centered = uv - 0.5;
half angle = atan2(uvs_centered.y, uvs_centered.x);
half radius = length(uvs_centered);

half whirl_coords = _Whirl_Density * angle + _Whirl_Twist * radius * 6.2831;
half mask_whirl = step(0.5, frac(whirl_coords / 3.14159));

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Visual demo

This shader converts UVs into polar coordinates, then modulates the pattern by combining angular and radial components. Using frac() and step() produces a clean, alternating swirl pattern with controllable density and twist.

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URP Shader Code

Shader "DecompiledArt/Patterns/Whirl/Whirl"
{
    Properties
    {
        _Tint_01("Tint_01", Color) = (1,1,1,1)
        _Tint_02("Tint_02", Color) = (0,0,0,1)
        _Whirl_Density("Whirl_Density", Range(1.0, 30.0)) = 10.0
        _Whirl_Twist("Whirl_Twist", Range(0.0, 10.0)) = 5.0
    }

    SubShader
    {
        Tags { "RenderType"="Opaque" "RenderPipeline" = "UniversalPipeline" }

        Pass
        {            
            ...
            

            half4 frag(Varyings IN) : SV_Target
            {
                half2 uvs_centered = IN.uvs - 0.5;
                half angle = atan2(uvs_centered.y, uvs_centered.x);
                half radius = length(uvs_centered);

                half whirl_coords = _Whirl_Density * angle + _Whirl_Twist * radius * 6.2831;
                half mask_whirl = step(0.5, frac(whirl_coords / 3.14159));

                half3 col_output = lerp(_Tint_01.rgb, _Tint_02.rgb, mask_whirl);
                return half4(col_output, 1.0);
            }

            ENDHLSL
        }
    }
}

URP Shader graph

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🔗 Related Functions

Frac • Step

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