ZoomShader.shader

Shader "Unlit/ZoomShader"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Zoom ("Zoom", Range(0,1)) = 0
        _Color ("Color", Color) = (1,1,1,1)
    }
    
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // make fog work
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

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

            struct v2f
            {
                float2 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            float _Zoom;
            fixed4 _Color;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                UNITY_TRANSFER_FOG(o,o.vertex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                // sample the texture
                float u = ceil(i.uv.x) * 0.5; // use ceil to round up uv
                float v = ceil(i.uv.y) * 0.5; // multiply by 0.5 to get the zoom effect from center

                float uLerp = lerp(i.uv.x, u, _Zoom); // lerp between the original uv and the rounded uv
                float vLerp = lerp(i.uv.y, v, _Zoom);
                
                fixed4 col = tex2D(_MainTex, float2(uLerp, vLerp));
                col *= _Color;
                // apply fog
                UNITY_APPLY_FOG(i.fogCoord, col);
                return col;
            }
            
            ENDCG
        }
    }
}