Hi, Why does this code draw full black instead of an ellipse unlike on https://www.shadertoy.com/view/MdfGWn Code (CSharp): Shader "Custom/Ellipse" { Properties { _MainTex ("Albedo (RGB)", 2D) = "white" {} } 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; uniform float4 _MainTex_TexelSize; struct Input { float2 uv_MainTex; }; const float a = 1.0; const float b = 3.0; const float g = 2048.0; float r = 0.9, e; float ellipse1(float2 p) { float f = length(p * float2(a, b)); return abs(f - r); } void surf (Input IN, inout SurfaceOutputStandard o) { e = 2.0 / g;// _MainTex_TexelSize.z; // float2 uv = (2.0 * IN.uv_MainTex - _MainTex_TexelSize.zw) / _MainTex_TexelSize.z; float2 uv = (2.0 * IN.uv_MainTex - float2(g, g)) / g; fixed f1 = ellipse1(uv); o.Albedo = f1; // c.rgb; o.Alpha = 1.0; } ENDCG } FallBack "Diffuse" }