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Modifying UVs using stereographic projection to create the illusion of a sphere.
Shader "Unlit/StereographicProjectionBubble"
{
Properties
{
_MainTex ("Texture", 2D) = "white" {}
_PanSpeed ("Pan Speed", Float) = 0.1
_Spherify ("Spherify", Range(0,1)) = 1
}
SubShader
{
Tags { "Queue"="Transparent" "RenderType"="Transparent" "PreviewType"="Plane" }
LOD 100
Blend SrcAlpha OneMinusSrcAlpha
Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
struct v2f
{
float4 pos : SV_POSITION;
float2 uv : TEXCOORD0;
};
sampler2D _MainTex;
float4 _MainTex_ST;
float _PanSpeed;
float _Spherify;
v2f vert (appdata_base v)
{
v2f o;
o.pos = UnityObjectToClipPos(v.vertex);
o.uv = v.texcoord.xy;
return o;
}
fixed4 frag (v2f i) : SV_Target
{
float2 centered_uv = i.uv * 2.0 - 1.0;
float z = sqrt(1.0 - saturate(dot(centered_uv.xy, centered_uv.xy)));
float2 spherified_uv = centered_uv / (z + 1.0);
float2 uv = spherified_uv * 0.5 + 0.5;
uv = lerp(i.uv, uv, _Spherify);
uv = TRANSFORM_TEX(uv, _MainTex);
uv.x += frac(_Time.y * _PanSpeed);
fixed4 col = tex2D(_MainTex, uv);
half sqrDist = dot(centered_uv.xy, centered_uv.xy);
half mask = 1.0 - sqrDist;
mask = saturate(mask / fwidth(mask));
col.a *= mask;
return col;
}
ENDCG
}
}
}
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